Homo sapiens is the only extant human species. The name is Latin for "wiseman" and was introduced in 1758 by Carl Linnaeus (who is himself the lectotype for the species).
Extinct species of the genus Homo include Homo erectus, extant during roughly 1.9 to 0.4 million years ago, and a number of other species (by some authors considered subspecies of either H. sapiens or H. erectus). The age of speciation of H. sapiens out of ancestral H. erectus (or an intermediate species such as Homo antecessor) is estimated to have been roughly 350,000 years ago. Sustained archaic admixture is known to have taken place both in Africa and (following the recent Out-Of-Africa expansion) in Eurasia, between about 100,000 and 30,000 years ago.
The term anatomically modern humans (AMH) is used to distinguish H. sapiens having an anatomy consistent with the range of phenotypes seen in contemporary humans from varieties of extinct archaic humans. This is useful especially for times and regions where anatomically modern and archaic humans co-existed, for example, in Paleolithic Europe.
Name and taxonomy
The binomial nameHomo sapiens was coined by Linnaeus, 1758. The Latin noun homō (genitive hominis) means "human being", while the participle sapiēns means "discerning, wise, sensible".
The species was initially thought to have emerged from a predecessor within the genus Homo around 300,000 to 200,000 years ago.
A problem with the morphological classification of "anatomically
modern" was that it would not have included certain extant populations.
For this reason, a lineage-based (cladistic) definition of H. sapiens has been suggested, in which H. sapiens
would by definition refer to the modern human lineage following the
split from the Neanderthal lineage. Such a cladistic definition would
extend the age of H. sapiens to over 500,000 years.
Extant human populations have historically been divided into subspecies, but since around the 1980s all extant groups have tended to be subsumed into a single species, H. sapiens, avoiding division into subspecies altogether.
Some sources show Neanderthals (H. neanderthalensis) as a subspecies (H. sapiens neanderthalensis). Similarly, the discovered specimens of the H. rhodesiensis species have been classified by some as a subspecies (H. sapiens rhodesiensis), although it remains more common to treat these last two as separate species within the genus Homo rather than as subspecies within H. sapiens.
The subspecies name H. sapiens sapiens
is sometimes used informally instead of "modern humans" or
"anatomically modern humans". It has no formal authority associated with
it. By the early 2000s, it had become common to use H. s. sapiens for the ancestral population of all contemporary humans, and as such it is equivalent to the binomial H. sapiens in the more restrictive sense (considering H. neanderthalensis a separate species).
Age and speciation process
Schematic representation of the emergence of H. sapiens from earlier species of Homo. The horizontal axis represents geographic location; the vertical axis represents time in millions of years ago (blue areas denote the presence of a certain species of Homo at a given time and place; late survival of robust australopithecines alongside Homo is indicated in purple). Based on Springer (2012), Homo heidelbergensis is shown as diverging into Neanderthals, Denisovans and H. sapiens. With the rapid expansion of H. sapiens after 60 kya, Neanderthals, Denisovans and unspecified archaic African hominins are shown as again subsumed into the H. sapiens lineage.
Derivation from H. erectus
A model of the phylogeny of H. sapiens during the Middle Paleolithic. The horizontal axis represents geographic location; the vertical axis represents time in thousands of years ago. Neanderthals, Denisovans and unspecified archaic African hominins are shown as admixed into the H. sapiens lineage. In addition, prehistoric Archaic Human and Eurasian admixture events in modern African populations are indicated.
The speciation of H. sapiens out of archaic human varieties derived from H. erectus is estimated as having taken place over 350,000 years ago, as the Khoisan split from other populations is dated between 260,000 and 350,000 years ago.
An alternative suggestion defines H. sapienscladistically as including the lineage of modern humans since the split from the lineage of Neanderthals, roughly 500,000 to 800,000 years ago.
The time of divergence between archaic H. sapiens and ancestors of Neanderthals and Denisovans caused by a genetic bottleneck of the latter was dated at 744,000 years ago, combined with repeated early admixture events and Denisovans diverging from Neanderthals 300 generations after their split from H. sapiens, as calculated by Rogers et al. (2017).
The derivation of a comparatively homogeneous single species of H. sapiens from more diverse varieties of archaic humans (all of which were descended from the early dispersal of H. erectus some 1.8 million years ago) was debated in terms of two competing models during the 1980s: "recent African origin" postulated the emergence of H. sapiens from a single source population in Africa, which expanded and led to the extinction of all other human varieties, while the "multiregional evolution" model postulated the survival of regional forms of archaic humans, gradually converging into the modern human varieties by the mechanism of clinal variation, via genetic drift, gene flow and selection throughout the Pleistocene.
Since the 2000s, the availability of data from archaeogenetics and population genetics has led to the emergence of a much more detailed picture, intermediate between the two competing scenarios outlined above: The recent Out-of-Africa expansion accounts for the predominant part of modern human ancestry, while there were also significant admixture events with regional archaic humans.
Since the 1970s, the Omo remains,
dated to some 195,000 years ago, have often been taken as the
conventional cut-off point for the emergence of "anatomically modern
humans". Since the 2000s, the discovery of older remains with comparable
characteristics, and the discovery of ongoing hybridization between
"modern" and "archaic" populations after the time of the Omo remains,
have opened up a renewed debate on the age of H. sapiens in journalistic publications. H. s. idaltu, dated to 160,000 years ago, has been postulated as an extinct subspecies of H. sapiens in 2003. H. neanderthalensis, which became extinct about 40,000 years ago, has also been classified as a subspecies, H. s. neanderthalensis.
H. heidelbergensis, dated 600,000 to 300,000 years ago,
has long been thought to be a likely candidate for the last common
ancestor of the Neanderthal and modern human lineages. However, genetic
evidence from the Sima de los Huesos fossils published in 2016 seems to suggest that H. heidelbergensis
in its entirety should be included in the Neanderthal lineage, as
"pre-Neanderthal" or "early Neanderthal", while the divergence time
between the Neanderthal and modern lineages has been pushed back to
before the emergence of H. heidelbergensis, to close to 800,000 years ago, the approximate time of disappearance of H. antecessor.
Early Homo sapiens
Skhul V (dated at about 80,000–120,000 years old) exhibiting a mix of archaic and modern traits.
The term Middle Paleolithic is intended to cover the time between the first emergence of H. sapiens (roughly 300,000 years ago) and the emergence of full behavioral modernity (roughly 50,000 years ago, corresponding to the start of the Upper Paleolithic).
Many of the early modern human finds, like those of Omo, Herto, Skhul, Jebel Irhoud and Peștera cu Oase exhibit a mix of archaic and modern traits. Skhul V, for example, has prominent brow ridges and a projecting face. However, the brain case
is quite rounded and distinct from that of the Neanderthals and is
similar to the brain case of modern humans. It is uncertain whether the
robust traits of some of the early modern humans like Skhul V reflects mixed ancestry or retention of older traits.
The "gracile" or lightly built skeleton of anatomically modern
humans has been connected to a change in behavior, including increased
cooperation and "resource transport".
There is evidence that the characteristic human brain
development, especially the prefrontal cortex, was due to "an
exceptional acceleration of metabolome
evolution ... paralleled by a drastic reduction in muscle strength. The
observed rapid metabolic changes in brain and muscle, together with the
unique human cognitive skills and low muscle performance, might reflect
parallel mechanisms in human evolution." The Schöningen spears
and their correlation of finds are evidence that complex technological
skills already existed 300,000 years ago, and are the first obvious
proof of an active (big game) hunt. H. heidelbergensis
already had intellectual and cognitive skills like anticipatory
planning, thinking and acting that so far have only been attributed to
modern man.
The ongoing admixture events within anatomically modern human
populations make it difficult to estimate the age of the matrilinear and
patrilinear most recent common ancestors of modern populations (Mitochondrial Eve and Y-chromosomal Adam).
Estimates of the age of Y-chromosomal Adam have been pushed back
significantly with the discovery of an ancient Y-chromosomal lineage in
2013, to likely beyond 300,000 years ago.
There have, however, been no reports of the survival of Y-chromosomal
or mitochondrial DNA clearly deriving from archaic humans (which would
push back the age of the most recent patrilinear or matrilinear ancestor
beyond 500,000 years).
Fossil teeth found at Qesem Cave
(Israel) and dated to between 400,000 and 200,000 years ago have been
compared to the dental material from the younger (120,000–80,000 years
ago) Skhul and Qafzeh hominins.
Dispersal and archaic admixture
Overview map of the peopling of the world by anatomically modern humans (numbers indicate dates in thousands of years ago [ka])
Dispersal of early H. sapiens begins soon after its emergence, as evidenced by the North African Jebel Irhoud finds (dated to between 280,000 and 350,000 years ago). There is indirect evidence for modern human presence in West Asia around 270,000 years ago and Dali Man from China is dated at 260,000 years ago.
Among extant populations, the Khoi-San (or "Capoid")
hunters-gatherers of Southern Africa may represent the human population
with the earliest possible divergence within the group Homo sapiens sapiens.
Their separation time has been estimated in a 2017 study to be as long
as between 260,000 and 350,000 years ago, compatible with the estimated
age of H. sapiens. H. s. idaltu, found at Middle Awash in Ethiopia, lived about 160,000 years ago, and H. sapiens lived at Omo Kibish in Ethiopia about 195,000 years ago. Fossil evidence for modern human presence in West Asia is ascertained for 177,000 years ago, and disputed fossil evidence suggests expansion as far as East Asia by 120,000 years ago.
In July 2019, anthropologists reported the discovery of 210,000 year old remains of a H. sapiens and 170,000 year old remains of a H. neanderthalensis in Apidima Cave, Peloponnese, Greece, more than 150,000 years older than previous H. sapiens finds in Europe.
A significant dispersal event, within Africa and to West Asia, is associated with the African megadroughts during MIS 5, beginning 130,000 years ago.
A 2011 study located the origin of basal population of contemporary
human populations at 130,000 years ago, with the Khoi-San representing
an "ancestral population cluster" located in southwestern Africa (near
the coastal border of Namibia and Angola).
Layer sequence at Ksar Akil in the Levantine corridor, and discovery of two fossils of Homo sapiens, dated to 40,800 to 39,200 years BP for "Egbert",and 42,400–41,700 BP for "Ethelruda".
While early modern human expansion in Sub-Saharan Africa
before 130 kya persisted, early expansion to North Africa and Asia
appears to have mostly disappeared by the end of MIS5 (75,000 years
ago), and is known only from fossil evidence and from archaic admixture. Asia was re-populated by early modern humans in the so-called "recent out-of-Africa migration" post-dating MIS5, beginning around 70,000 years ago. In this expansion, bearers of mt-DNA haplogroup L3 left East Africa, likely reaching Arabia via the Bab-el-Mandeb, and in the Great Coastal Migration spread to South Asia, Maritime South Asia and Oceania by 65,000 years ago, while Europe, East and North Asia, and possibly the Americas, were reached by 50,000 years ago.
Evidence for the overwhelming contribution of this "recent" (L3-derived) expansion to all non-African populations was established based on mitochondrial DNA, combined with evidence based on physical anthropology of archaic specimens, during the 1990s and 2000s. The assumption of complete replacement has been revised in the 2010s with the discovery of admixture events (introgression) of populations of H. sapiens
with populations of archaic humans over the period of between roughly
100,000 and 30,000 years ago, both in Eurasia and in Sub-Saharan Africa.
Neanderthal admixture,
in the range of 1-4%, is found in all modern populations outside of
Africa, including in Europeans, Asians, Papuan New Guineans, Australian
Aboriginals, and Native Americans. This suggests that interbreeding between Neanderthals and anatomically modern humans took place after the recent "out of Africa" migration, likely between 60,000 and 40,000 years ago.
Recent admixture analyses have added to the complexity, finding that
Eastern Neanderthals derive up to 2% of their ancestry from anatomically
modern humans who left Africa some 100 kya. The extent of Neanderthal admixture (and introgression
of genes acquired by admixture) varies significantly between
contemporary racial groups, being absent in Africans, intermediate in
Europeans and highest in East Asians. Certain genes related to UV-light
adaptation introgressed from Neanderthals have been found to have been
selected for in East Asians specifically from 45,000 years ago until
around 5,000 years ago. The extent of archaic admixture is of the order of about 1% to 4% in Europeans and East Asians, and highest among Melanesians (Denisova hominin admixture), at 4% to 6%. Cumulatively, about 20% of the Neanderthal genome is estimated to remain present spread in contemporary populations.
Anatomy
Known
archaeological remains of Anatomically Modern Humans in Europe and
Africa, directly dated, calibrated carbon dates as of 2013.
Generally, modern humans are more lightly built (or more "gracile") than the more "robust" archaic humans. Nevertheless, contemporary humans exhibit high variability in many physiological traits,
and may exhibit remarkable "robustness". There are still a number of
physiological details which can be taken as reliably differentiating the
physiology of Neanderthals vs. anatomically modern humans.
Anatomical modernity
The term "anatomically modern humans" (AMH) is used with varying
scope depending on context, to distinguish "anatomically modern" Homo sapiens from archaic humans such as Neanderthals and Middle and Lower Paleolithic hominins with transitional features intermediate between H. erectus, Neanderthals and early AMH called archaic Homo sapiens. In a convention popular in the 1990s, Neanderthals were classified as a subspecies of H. sapiens, as H. s. neanderthalensis, while AMH (or European early modern humans, EEMH) was taken to refer to "Cro-Magnon" or H. s. sapiens. Under this nomenclature (Neanderthals considered H. sapiens), the term "anatomically modern Homo sapiens" (AMHS) has also been used to refer to EEMH ("Cro-Magnons"). It has since become more common to designate Neanderthals as a separate species, H. neanderthalensis, so that AMH in the European context refers to H. sapiens (but the question is by no means resolved).
In this more narrow definition of H. sapiens, the subspecies H. s. idaltu, discovered in 2003, also falls under the umbrella of "anatomically modern". The recognition of H. s. idaltu as a valid subspecies of the anatomically modern human lineage would justify the description of contemporary humans with the subspecies name H. s. sapiens.
A further division of AMH into "early" or "robust" vs.
"post-glacial" or "gracile" subtypes has since been used for
convenience. The emergence of "gracile AMH" is taken to reflect a
process towards a smaller and more fine-boned skeleton beginning around
50,000–30,000 years ago.
The cranium lacks a pronounced occipital bun
in the neck, a bulge that anchored considerable neck muscles in
Neanderthals. Modern humans, even the earlier ones, generally have a
larger fore-brain than the archaic people, so that the brain sits above
rather than behind the eyes. This will usually (though not always) give a
higher forehead, and reduced brow ridge.
Early modern people and some living people do however have quite
pronounced brow ridges, but they differ from those of archaic forms by
having both a supraorbital foramen or notch, forming a groove through the ridge above each eye.
This splits the ridge into a central part and two distal parts. In
current humans, often only the central section of the ridge is preserved
(if it is preserved at all). This contrasts with archaic humans, where
the brow ridge is pronounced and unbroken.
Modern humans commonly have a steep, even vertical forehead whereas their predecessors had foreheads that sloped strongly backwards. According to Desmond Morris, the vertical forehead in humans plays an important role in human communication through eyebrow movements and forehead skin wrinkling.
Brain size in both Neanderthals and AMH is significantly larger on average (but overlapping in range) than brain size in H. erectus.
Neanderthal and AMH brain sizes are in the same range, but there are
differences in the relative sizes of individual brain areas, with
significantly larger visual systems in Neanderthals than in AMH.
Jaw anatomy
Compared to archaic people, anatomically modern humans have smaller, differently shaped teeth.
This results in a smaller, more receded dentary, making the rest of the
jaw-line stand out, giving an often quite prominent chin. The central
part of the mandible forming the chin carries a triangularly shaped area
forming the apex of the chin called the mental trigon, not found in archaic humans.
Particularly in living populations, the use of fire and tools requires
fewer jaw muscles, giving slender, more gracile jaws. Compared to
archaic people, modern humans have smaller, lower faces.
Body skeleton structure
The body skeletons of even the earliest and most robustly built
modern humans were less robust than those of Neanderthals (and from what
little we know from Denisovans), having essentially modern proportions.
Particularly regarding the long bones of the limbs, the distal bones
(the radius/ulna and tibia/fibula) are nearly the same size or slightly shorter than the proximal bones (the humerus and femur).
In ancient people, particularly Neanderthals, the distal bones were
shorter, usually thought to be an adaptation to cold climate. The same adaptation can be found in some modern people living in the polar regions.
Height
ranges overlap between Neanderthals and AMH, with Neanderthal averages
cited as 164 to 168 cm (65 to 66 in) and 152 to 156 cm (60 to 61 in) for
males and females, respectively. By comparison, contemporary national averages
range between 158 to 184 cm (62 to 72 in) in males and 147 to 172 cm
(58 to 68 in) in females. Neanderthal ranges approximate the height
distribution measured among Malay people, for one.
Recent evolution
Following the peopling of Africa some 130,000 years ago, and the recent Out-of-Africa expansion some 70,000 to 50,000 years ago, some sub-populations of H. sapiens have been essentially isolated for tens of thousands of years prior to the early modern Age of Discovery. Combined with archaic admixture this has resulted in significant genetic variation, which in some instances has been shown to be the result of directional selection taking place over the past 15,000 years, i.e. significantly later than possible archaic admixture events.
Some climatic adaptations, such as high-altitude adaptation in humans, are thought to have been acquired by archaic admixture. Introgression of genetic variants acquired by Neanderthal admixture have different distributions in European and East Asians,
reflecting differences in recent selective pressures. A 2014 study
reported that Neanderthal-derived variants found in East Asian
populations showed clustering in functional groups related to immune and haematopoietic pathways, while European populations showed clustering in functional groups related to the lipid catabolic process. A 2017 study found correlation of Neanderthal admixture in phenotypic traits in modern European populations.
Physiological or phenotypical changes have been traced to Upper Paleolithic mutations, such as the East Asian variant of the EDAR gene, dated to c. 35,000 years ago.
Recent divergence of Eurasian lineages was sped up significantly during the Last Glacial Maximum, the Mesolithic and the Neolithic, due to increased selection pressures and due to founder effects associated with migration. Alleles predictive of light skin have been found in Neanderthals, but the alleles for light skin in Europeans and East Asians, associated with KITLG and ASIP, are (as of 2012) thought to have not been acquired by archaic admixture but recent mutations since the LGM. Phenotypes associated with the "white" or "Caucasian" populations of Western Eurasian stock emerge during the LGM, from about 19,000 years ago. Average cranial capacity in modern human populations varies in the range of 1,200 to 1,450 cm3
(adult male averages). Larger cranial volume is associated with
climatic region, the largest averages being found in populations of Siberia and the Arctic. Both Neanderthal and EEMH
had somewhat larger cranial volumes on average than modern Europeans,
suggesting the relaxation of selection pressures for larger brain volume
after the end of the LGM.
An even more recent adaptation has been proposed for the Austronesian Sama-Bajau, developed under selection pressures associated with subsisting on freediving over the past thousand years or so.
Behavioral modernity
Lithic Industries of early Homo sapiens at Blombos Cave (M3 phase, MIS 5), Southern Cape, South Africa (c. 105 – 90 Ka)
There is considerable debate regarding whether the earliest
anatomically modern humans behaved similarly to recent or existing
humans. Behavioral modernity is taken to include fully developed language (requiring the capacity for abstract thought), artistic expression, early forms of religious behavior, increased cooperation and the formation of early settlements, and the production of articulated tools from lithic cores, bone or antler. The term Upper Paleolithic is intended to cover the period since the rapid expansion of modern humans throughout Eurasia, which coincides with the first appearance of Paleolithic art such as cave paintings and the development of technological innovation such as the spear-thrower.
The Upper Paleolithic begins around 50,000 to 40,000 years ago, and
also coincides with the disappearance of archaic humans such as the Neanderthals.
Bifacial silcrete point of early Homo sapiens, from M1 phase (71,000 BCE) layer of Blombos Cave, South Africa
The term "behavioral modernity" is somewhat disputed. It is most
often used for the set of characteristics marking the Upper Paleolithic,
but some scholars use "behavioral modernity" for the emergence of H. sapiens around 200,000 years ago, while others use the term for the rapid developments occurring around 50,000 years ago. It has been proposed that the emergence of behavioral modernity was a gradual process.
In January 2018, it was announced that modern human finds at
Misliya cave, Israel, in 2002, had been dated to around 185,000 years
ago, the earliest evidence of their out of Africa migration.
The earliest H. sapiens (AMH) found in Europe are the "Cro-Magnon" (named after the site of first discovery in France), beginning about 40,000 to 35,000 years ago. These are also known as "European early modern humans" in contrast to the preceding Neanderthals.
The equivalent of the Eurasian Upper Paleolithic in African archaeology is known as the Later Stone Age,
also beginning roughly 40,000 years ago. While most clear evidence for
behavioral modernity uncovered from the later 19th century was from
Europe, such as the Venus figurines and other artefacts from the Aurignacian,
more recent archaeological research has shown that all essential
elements of the kind of material culture typical of contemporary San hunter-gatherers in Southern Africa was also present by least 40,000 years ago, including digging sticks of similar materials used today, ostrich egg shell beads, bone arrow heads with individual maker's marks etched and embedded with red ochre, and poison applicators.
There is also a suggestion that "pressure flaking best explains the
morphology of lithic artifacts recovered from the c. 75-ka Middle Stone
Age levels at Blombos Cave, South Africa. The technique was used during
the final shaping of Still Bay bifacial points made on heat‐treated
silcrete."
Both pressure flaking and heat treatment of materials were previously
thought to have occurred much later in prehistory, and both indicate a
behaviourally modern sophistication in the use of natural materials.
Further reports of research on cave sites along the southern African
coast indicate that "the debate as to when cultural and cognitive
characteristics typical of modern humans first appeared" may be coming
to an end, as "advanced technologies with elaborate chains of
production" which "often demand high-fidelity transmission and thus
language" have been found at Pinnacle Point Site 5–6. These have been
dated to approximately 71,000 years ago. The researchers suggest that
their research "shows that microlithic technology originated early in
South Africa, evolved over a vast time span (c. 11,000 years), and was
typically coupled to complex heat treatment that persisted for nearly
100,000 years. Advanced technologies in Africa
were early and enduring; a small sample of excavated sites in Africa is
the best explanation for any perceived 'flickering' pattern."
These results suggest that Late Stone Age foragers in Sub-Saharan
Africa had developed modern cognition and behaviour by at least 50,000
years ago.
The change in behavior has been speculated to have been a consequence
of an earlier climatic change to much drier and colder conditions
between 135,000 and 75,000 years ago.
This might have led to human groups who were seeking refuge from the
inland droughts, expanded along the coastal marshes rich in shellfish
and other resources. Since sea levels were low due to so much water tied
up in glaciers, such marshlands would have occurred all along the southern coasts of Eurasia. The use of rafts
and boats may well have facilitated exploration of offshore islands and
travel along the coast, and eventually permitted expansion to New
Guinea and then to Australia.
Dementia is a broad category of brain diseases that cause a long-term and often gradual decrease in the ability to think and remember that is great enough to affect a person's daily functioning. Other common symptoms include emotional problems, difficulties with language, and a decrease in motivation. A person's consciousness is usually not affected.
A dementia diagnosis requires a change from a person's usual mental
functioning and a greater decline than one would expect due to aging. These diseases also have a significant effect on a person's caregivers.
There is no known cure for dementia. Cholinesterase inhibitors such as donepezil are often used and may be beneficial in mild to moderate disorder. Overall benefit, however, may be minor. There are many measures that can improve the quality of life of people with dementia and their caregivers. Cognitive and behavioral interventions may be appropriate. Educating and providing emotional support to the caregiver is important. Exercise programs may be beneficial with respect to activities of daily living and potentially improve outcomes. Treatment of behavioral problems with antipsychotics is common but not usually recommended due to the little benefit and side effects, including an increased risk of death.
Globally, dementia affected about 46 million people in 2015. About 10% of people develop the disorder at some point in their lives. It becomes more common with age.
About 3% of people between the ages of 65–74 have dementia, 19% between
75 and 84, and nearly half of those over 85 years of age. In 2013 dementia resulted in about 1.7 million deaths up from 0.8 million in 1990. As more people are living longer, dementia is becoming more common in the population as a whole.
For people of a specific age, however, it may be becoming less
frequent, at least in the developed world, due to a decrease in risk
factors. It is one of the most common causes of disability amongst the old. It is believed to result in economic costs of US$604 billion a year. People with dementia are often physically or chemically restrained to a greater degree than necessary, raising issues of human rights. Social stigma against those affected is common.
Signs and symptoms
A drawing of a woman diagnosed as having dementia.
An old man diagnosed with senile dementia
The symptoms of dementia vary across types and stages of the diagnosis. The most common affected areas include memory, visual-spatial, language, attention and problem solving.
Most types of dementia are slow and progressive. By the time the person
shows signs of the disorder, the process in the brain has been
happening for a long time. It is possible for a patient to have two
types of dementia at the same time. About 10% of people with dementia
have what is known as mixed dementia, which is usually a combination of Alzheimer's disease and another type of dementia such as frontotemporal dementia or vascular dementia.
Neuropsychiatric symptoms that may be present are termed Behavioural and psychological symptoms of dementia (BPSD) and these can include:
Memory distortions (believing that a memory has already happened
when it has not, thinking an old memory is a new one, combining two
memories, or confusing the people in a memory)
Wandering or restlessness
Perception and visual problems
Behavioral and psychological symptoms of dementia almost always occur in all types of dementia and may manifest as:
When people with dementia are put in circumstances beyond their abilities, there may be a sudden change to crying or anger (a "catastrophic reaction").
Psychosis (often delusions of persecution) and agitation/aggression also often accompany dementia.
Mild cognitive impairment
In
the first stages of dementia, the signs and symptoms of the disorder
may be subtle. Often, the early signs of dementia only become apparent
when looking back in time. The earliest stage of dementia is called mild cognitive impairment (MCI). 70% of those diagnosed with MCI progress to dementia at some point.
In MCI, changes in the person's brain have been happening for a long
time, but the symptoms of the disorder are just beginning to show. These
problems, however, are not yet severe enough to affect the person's
daily function. If they do, it is considered dementia. A person with MCI
scores between 27 and 30 on the Mini-Mental State Examination
(MMSE), which is a normal score. They may have some memory trouble and
trouble finding words, but they solve everyday problems and handle their
own life affairs well.
Early stages
In the early stage of dementia, the person begins to show symptoms
noticeable to the people around them. In addition, the symptoms begin to
interfere with daily activities. The person usually scores between a 20
and 25 on the MMSE.
The symptoms are dependent on the type of dementia a person has. The
person may begin to have difficulty with more complicated chores and
tasks around the house or at work. The person can usually still take
care of him or herself but may forget things like taking pills or doing
laundry and may need prompting or reminders.
The symptoms of early dementia usually include memory difficulty,
but can also include some word-finding problems (anomia) and problems
with planning and organizational skills (executive function).
One very good way of assessing a person's impairment is by asking if
they are still able to handle their finances independently. This is
often one of the first things to become problematic. Other signs might
be getting lost in new places, repeating things, personality changes,
social withdrawal and difficulties at work.
When evaluating a person for dementia, it is important to
consider how the person was able to function five or ten years earlier.
It is also important to consider a person's level of education when
assessing for loss of function. For example, an accountant who can no
longer balance a checkbook would be more concerning than a person who
had not finished high school or had never taken care of his/her own
finances.
In Alzheimer's dementia the most prominent early symptom is
memory difficulty. Others include word-finding problems and getting
lost. In other types of dementia, like dementia with Lewy bodies and
fronto-temporal dementia, personality changes and difficulty with
organization and planning may be the first signs.
Middle stages
As
dementia progresses, the symptoms first experienced in the early stages
of the dementia generally worsen. The rate of decline is different for
each person. A person with moderate dementia scores between 6–17 on the
MMSE. For example, people with Alzheimer's dementia in the moderate
stages lose almost all new information very quickly. People with
dementia may be severely impaired in solving problems, and their social
judgment is usually also impaired. They cannot usually function outside
their own home, and generally should not be left alone. They may be able
to do simple chores around the house but not much else, and begin to
require assistance for personal care and hygiene other than simple
reminders.
Late stages
People
with late-stage dementia typically turn increasingly inward and need
assistance with most or all of their personal care. Persons with
dementia in the late stages usually need 24-hour supervision to ensure
personal safety, as well as to ensure that basic needs are being met. If
left unsupervised, a person with late-stage dementia may wander or
fall, may not recognize common dangers around them such as a hot stove,
may not realize that they need to use the bathroom or become unable to
control their bladder or bowels (incontinent).
Changes in eating frequently occur. Caregivers of people with late-stage dementia often provide pureed diets,
thickened liquids, and assistance in eating, to prolong their lives, to
cause them to gain weight, to reduce the risk of choking, and to make
feeding the person easier.
The person's appetite may decline to the point that the person does not
want to eat at all. They may not want to get out of bed, or may need
complete assistance doing so. Commonly, the person no longer recognizes
familiar people. They may have significant changes in sleeping habits or
have trouble sleeping at all.
Causes
Reversible causes
Causes of easily reversible dementia include hypothyroidism, vitamin B12 deficiency, Lyme disease, and neurosyphilis.
All people with memory difficulty should be checked for hypothyroidism
and B12 deficiency. For Lyme disease and neurosyphilis, testing should
be done if there are risk factors for those diseases in the person.
Because risk f
actors are often difficult to determine, testing for neurosyphilis and
Lyme disease, as well as other mentioned factors, may be undertaken as a
matter of course in cases where dementia is suspected.Hearing loss may also be associated with dementia. There is tentative evidence that hearing aids may have some benefit.
Alzheimer's disease
Brain atrophy in severe Alzheimer's
Alzheimer's disease accounts for 50% to 70% of cases of dementia. The most common symptoms of Alzheimer's disease are short-term memory loss and word-finding difficulties.
People with Alzheimer's disease also have trouble with visual-spatial
areas (for example, they may begin to get lost often), reasoning,
judgment, and insight. Insight refers to whether or not the person
realizes they have memory problems.
Common early symptoms of Alzheimer's include repetition, getting
lost, difficulties keeping track of bills, problems with cooking
especially new or complicated meals, forgetting to take medication, and
word-finding problems.
The part of the brain most affected by Alzheimer's is the hippocampus. Other parts of the brain that show shrinking (atrophy) include the temporal and parietal lobes.
Although this pattern suggests Alzheimer's, the brain shrinkage in
Alzheimer's disease is very variable, and a scan of the brain cannot
actually make the diagnosis. The relationship between undergoing anesthesia and AD is unclear.
Vascular dementia
Vascular dementia is the cause of at least 20% of dementia cases, making it the second most common cause of dementia.
It is caused by disease or injury affecting the blood supply to the
brain, typically involving a series of minor strokes. The symptoms of
this dementia depend on where in the brain the strokes have occurred and
whether the vessels are large or small.
Multiple injuries can cause progressive dementia over time, while a
single injury located in an area critical for cognition (i.e.
hippocampus, thalamus) can lead to sudden cognitive decline.
Dementia with Lewy bodies (DLB) is a dementia that has the primary symptoms of visual hallucinations and "Parkinsonism". Parkinsonism is the symptoms of Parkinson's disease,
which includes tremor, rigid muscles, and a face without emotion. The
visual hallucinations in DLB are generally very vivid hallucinations of
people or animals and they often occur when someone is about to fall
asleep or just waking up. Other prominent symptoms include problems with
attention, organization, problem solving and planning (executive
function), and difficulty with visual-spatial function.
Again, imaging studies cannot necessarily make the diagnosis of
DLB, but some signs are particularly common. A person with DLB often
shows occipital hypoperfusion on SPECT scan or occipital hypometabolism on a PET scan. Generally, a diagnosis of DLB is straightforward and unless it is complicated, a brain scan is not always necessary.
Frontotemporal dementia
Frontotemporal dementias
(FTDs) are characterized by drastic personality changes and language
difficulties. In all FTDs, the person has a relatively early social
withdrawal and early lack of insight into the disorder. Memory problems
are not a main feature of this disorder.
There are six main types of FTD. The first has major symptoms in
the area of personality and behavior. This is called behavioral variant
FTD (bv-FTD) and is the most common. In bv-FTD, the person shows a
change in personal hygiene, becomes rigid in their thinking, and rarely
recognize that there is a problem, they are socially withdrawn, and
often have a drastic increase in appetite. They may also be socially
inappropriate. For example, they may make inappropriate sexual comments,
or may begin using pornography openly when they had not before. One of
the most common signs is apathy, or not caring about anything. Apathy,
however, is a common symptom in many different dementias.
Two types of FTD feature language problems (aphasia)
as the main symptom. One type is called semantic variant primary
progressive aphasia (SV-PPA). The main feature of this is the loss of
the meaning of words. It may begin with difficulty naming things. The
person eventually may also lose the meaning of objects as well. For
example, a drawing of a bird, dog, and an airplane in someone with FTD
may all appear just about the same.
In a classic test for this, a patient is shown a picture of a pyramid
and below there is a picture of both a palm tree and a pine tree. The
person is asked to say which one goes best with the pyramid. In SV-PPA
the person would not be able to answer that question. The other type is
called non-fluent agrammatic variant primary progressive aphasia
(NFA-PPA). This is mainly a problem with producing speech. They have
trouble finding the right words, but mostly they have a difficulty
coordinating the muscles they need to speak. Eventually, someone with
NFA-PPA only uses one-syllable words or may become totally mute.
Progressive supranuclear palsy
(PSP) is a form of FTD that is characterized by problems with eye
movements. Generally the problems begin with difficulty moving the eyes
up or down (vertical gaze palsy). Since difficulty moving the eyes
upward can sometimes happen in normal aging, problems with downward eye
movements are the key in PSP. Other key symptoms of PSP include falling
backwards, balance problems, slow movements, rigid muscles,
irritability, apathy, social withdrawal, and depression. The person may
also have certain "frontal lobe signs" such as perseveration, a grasp
reflex and utilization behavior
(the need to use an object once you see it). People with PSP often have
progressive difficulty eating and swallowing, and eventually with
talking as well. Because of the rigidity and slow movements, PSP is
sometimes misdiagnosed as Parkinson's disease. On scans of the brain, the midbrain
of people with PSP is generally shrunken (atrophied), but there are no
other common brain abnormalities visible on images of the person's
brain.
Corticobasal degeneration
(CBD) is a rare form of FTD that is characterized by many different
types of neurological problems that get progressively worse over time.
This is because the disorder affects the brain in many different places,
but at different rates. One common sign is difficulty with using only
one limb. One symptom that is extremely rare in any condition other than
corticobasal degeneration is the "alien limb." The alien limb is a limb
of the person that seems to have a mind of its own, it moves without
control of the person's brain. Other common symptoms include jerky
movements of one or more limbs (myoclonus),
symptoms that are different in different limbs (asymmetric), difficulty
with speech that is due to not being able to move the mouth muscles in a
coordinated way, numbness and tingling of the limbs and neglecting one
side of the person's vision or senses. In neglect, a person ignores the
opposite side of the body from the one that has the problem. For
example, a person may not feel pain on one side, or may only draw half
of a picture when asked. In addition, the person's affected limbs may be
rigid or have muscle contractions causing strange repetitive movements (dystonia). The area of the brain most often affected in corticobasal degeneration is the posterior frontal lobe and parietal lobe. Still, many other part of the brain can be affected.
Finally, there is FT dementia associated with MND (FTD-MND) in
which the symptoms of FTD (behavior, language and movement problems)
co-occur with Motor Neurone Disease (death of motor neurons).
There
are many other medical and neurological conditions in which dementia
only occurs late in the illness. For example, a proportion of patients
with Parkinson's disease develop dementia, though widely varying figures are quoted for this proportion. When dementia occurs in Parkinson's disease, the underlying cause may be dementia with Lewy bodies or Alzheimer's disease, or both. Cognitive impairment also occurs in the Parkinson-plus syndromes of progressive supranuclear palsy and corticobasal degeneration (and the same underlying pathology may cause the clinical syndromes of frontotemporal lobar degeneration). Although the acute porphyrias may cause episodes of confusion and psychiatric disturbance, dementia is a rare feature of these rare diseases.
Aside from those mentioned above, inherited conditions that can cause dementia (alongside other symptoms) include:
Mild cognitive impairment
means that the person exhibits memory or thinking difficulties, but
those difficulties are not severe enough to meet criteria for a
diagnosis of dementia. They should score between 25–30 on the MMSE. Around 70% of people with MCI go on to develop some form of dementia.
MCI is generally divided into two categories. The first is one that is
primarily memory loss (amnestic MCI). The second category is anything
that is not primarily memory difficulties (non-amnestic MCI). People
with primarily memory problems generally go on to develop Alzheimer's
disease. People with the other type of MCI may go on to develop other
types of dementia.
Diagnosis of MCI is often difficult, as cognitive testing may be normal. Often, more in-depth neuropsychological testing is necessary to make the diagnosis. the most commonly used criteria are called the Peterson criteria and include:
Memory or other cognitive (thought-processing) complaint by the person or a person who knows the patient well.
The person must have a memory or other cognitive problem as compared to a person of the same age and level of education.
The problem must not be severe enough to affect the person's daily function.
Dementia that begins gradually and worsens progressively over several years is usually caused by neurodegenerative disease—that
is, by conditions that affect only or primarily the neurons of the
brain and cause gradual but irreversible loss of function of these
cells. Less commonly, a non-degenerative condition may have secondary
effects on brain cells, which may or may not be reversible if the
condition is treated.
Causes of dementia depend on the age when symptoms begin. In the
elderly population (usually defined in this context as over 65 years of
age), a large majority of dementia cases are caused by Alzheimer's disease, vascular dementia, or both. Dementia with Lewy bodies is another commonly exhibited form, which again may occur alongside either or both of the other causes. Hypothyroidism sometimes causes slowly progressive cognitive impairment as the main symptom, and this may be fully reversible with treatment. Normal pressure hydrocephalus,
though relatively rare, is important to recognize since treatment may
prevent progression and improve other symptoms of the condition.
However, significant cognitive improvement is unusual.
Hearing loss is linked with dementia with a greater degree of hearing loss tied to a higher risk. One hypothesis is that as hearing loss increases, cognitive resources are redistributed to auditory perception to the detriment of other cognitive processes. The second hypothesis is that hearing loss leads to social isolation which negatively affect the cognitive functions.
Diagnosis
As
seen above, there are many specific types and causes of dementia, often
showing slightly different symptoms. However, the symptoms are very
similar and it is usually difficult to diagnose the type of dementia by
symptoms alone. Diagnosis may be aided by brain scanning techniques. In many cases, the diagnosis cannot be absolutely sure except with a brain biopsy, but this is very rarely recommended (though it can be performed at autopsy). In those who are getting older, general screening for cognitive impairment using cognitive testing or early diagnosis of dementia has not been shown to improve outcomes. However, it has been shown that screening exams are useful in those people over the age of 65 with memory complaints.
Normally, symptoms must be present for at least six months to support a diagnosis. Cognitive dysfunction of shorter duration is called delirium.
Delirium can be easily confused with dementia due to similar symptoms.
Delirium is characterized by a sudden onset, fluctuating course, a short
duration (often lasting from hours to weeks), and is primarily related
to a somatic (or medical) disturbance. In comparison, dementia has
typically a long, slow onset (except in the cases of a stroke or
trauma), slow decline of mental functioning, as well as a longer
duration (from months to years).
Some mental illnesses, including depression and psychosis, may produce symptoms that must be differentiated from both delirium and dementia. Therefore, any dementia evaluation should include a depression screening such as the Neuropsychiatric Inventory or the Geriatric Depression Scale.
Physicians used to think that anyone who came in with memory complaints
had depression and not dementia (because they thought that those with
dementia are generally unaware of their memory problems). This is called
pseudodementia. However, in recent years researchers have realized that
many older people with memory complaints in fact have MCI, the earliest
stage of dementia. Depression should always remain high on the list of
possibilities, however, for an elderly person with memory trouble.
Changes in thinking, hearing and vision are associated with
normal ageing and can cause problems when diagnosing dementia due to the
similarities.
There are some brief tests (5–15 minutes) that have reasonable reliability to screen for dementia.
While many tests have been studied, presently the mini mental state examination
(MMSE) is the best studied and most commonly used. The MMSE is a useful
tool for helping to diagnose dementia if the results are interpreted
along with an assessment of a person's personality, their ability to
perform activities of daily living, and their behaviour. Other cognitive tests include the abbreviated mental test score (AMTS), the, Modified Mini-Mental State Examination (3MS), the Cognitive Abilities Screening Instrument (CASI), the Trail-making test, and the clock drawing test. The MoCA (Montreal Cognitive Assessment) is a very reliable screening test and is available online for free in 35 different languages. The MoCA has also been shown somewhat better at detecting mild cognitive impairment than the MMSE. Brief cognitive tests may be affected by factors such as age, education and ethnicity.
Another approach to screening for dementia is to ask an informant
(relative or other supporter) to fill out a questionnaire about the
person's everyday cognitive functioning. Informant questionnaires
provide complementary information to brief cognitive tests. Probably the
best known questionnaire of this sort is the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). There is not sufficient evidence to determine how accurate the IQCODE is for diagnosing or predicting dementia.
The Alzheimer's Disease Caregiver Questionnaire is another tool. It is
about 90% accurate for Alzheimer's and can be completed online or in the
office by a caregiver. On the other hand, the General Practitioner Assessment Of Cognition
combines both, a patient assessment and an informant interview. It was
specifically designed for the use in the primary care setting.
Clinical neuropsychologists provide diagnostic consultation
following administration of a full battery of cognitive testing, often
lasting several hours, to determine functional patterns of decline
associated with varying types of dementia. Tests of memory, executive
function, processing speed, attention, and language skills are relevant,
as well as tests of emotional and psychological adjustment. These tests
assist with ruling out other etiologies and determining relative
cognitive decline over time or from estimates of prior cognitive
abilities.
Instead of using “mild or early stage”, “middle stage”, and “late
stage” dementia as descriptors, there are scales that that allow more
details descriptions. These scales include: Global Deterioration Scale
for Assessment of Primary Degenerative Dementia (GDS or Reisberg Scale), Functional Assessment Staging Test (FAST), and Clinical Dementia Rating (CDR).
A CT scan or magnetic resonance imaging
(MRI scan) is commonly performed, although these tests do not pick up
diffuse metabolic changes associated with dementia in a person that
shows no gross neurological problems (such as paralysis or weakness) on
neurological exam. CT or MRI may suggest normal pressure hydrocephalus,
a potentially reversible cause of dementia, and can yield information
relevant to other types of dementia, such as infarction (stroke) that would point at a vascular type of dementia.
The functional neuroimaging modalities of SPECT and PET
are more useful in assessing long-standing cognitive dysfunction, since
they have shown similar ability to diagnose dementia as a clinical exam
and cognitive testing. The ability of SPECT to differentiate the vascular cause (i.e., multi-infarct dementia) from Alzheimer's disease dementias, appears superior to differentiation by clinical exam.
Recent research has established the value of PET imaging using
carbon-11 Pittsburgh Compound B as a radiotracer (PIB-PET) in predictive
diagnosis of various kinds of dementia, in particular Alzheimer's disease.
Studies from Australia have found PIB-PET 86% accurate in predicting
which patients with mild cognitive impairment will develop Alzheimer's
disease within two years. In another study, carried out using 66
patients seen at the University of Michigan, PET studies using either
PIB or another radiotracer, carbon-11 dihydrotetrabenazine (DTBZ), led
to more accurate diagnosis for more than one-fourth of patients with
mild cognitive impairment or mild dementia.
Prevention
A number of factors can decrease the risk of dementia.
A group of efforts is believed to be able to prevent a third of cases
and include early education, treating high blood pressure, preventing
obesity, preventing hearing loss, treating depression, being active, preventing diabetes, not smoking, and preventing social isolation. The decreased risk with a healthy lifestyle is seen even in those with a high genetic risk.
A 2018 review however concluded that no medications have good evidence
of a preventative effect including blood pressure medications.
Among otherwise healthy older people, computerized cognitive training may improve memory. However it is not known if it prevents dementia. Exercise has poor evidence of preventing dementia. In those with normal mental function evidence for medications is poor. The same applies to supplements.
Except for the treatable types listed above, there is no cure. Cholinesterase inhibitors are often used early in the disorder course; however, benefit is generally small.[8][88]
Cognitive and behavioral interventions may be appropriate. There is
some evidence that educating and providing support for the person with
dementia, as well as caregivers and family members, improves outcomes.[89] Exercise programs are beneficial with respect to activities of daily living and potentially improve dementia.
Psychological therapies
Psychological therapies for dementia include some limited evidence for reminiscence therapy
(namely, some positive effects in the areas of quality of life,
cognition, communication and mood – the first three particularly in care
home settings), some benefit for cognitive reframing for caretakers, unclear evidence for validation therapy, and tentative evidence for mental exercises, such as cognitive stimulation programs for people with mild to moderate dementia.
Reminiscence therapy can improve quality of life, cognition,
communication, and possibly mood in people with dementia in some
circumstances, although all of these benefits may be small.
Adult daycare
centers as well as special care units in nursing homes often provide
specialized care for dementia patients. Adult daycare centers offer
supervision, recreation, meals, and limited health care to participants,
as well as providing respite for caregivers. In addition, home care
can provide one-on-one support and care in the home allowing for more
individualized attention that is needed as the disorder progresses.
Psychiatric nurses can make a distinctive contribution to people's
mental health.
Since dementia impairs normal communication due to changes in
receptive and expressive language, as well as the ability to plan and
problem solve, agitated behaviour is often a form of communication for
the person with dementia. Actively searching for a potential cause, such
as pain, physical illness, or overstimulation can be helpful in
reducing agitation.
Additionally, using an "ABC analysis of behaviour" can be a useful tool
for understanding behavior in people with dementia. It involves looking
at the antecedents (A), behavior (B), and consequences (C) associated
with an event to help define the problem and prevent further incidents
that may arise if the person's needs are misunderstood.
The strongest evidence for non-pharmacological therapies for the
management of changed behaviours in dementia is for using such
approaches. There is low quality evidence that regular (at least five sessions of) music therapy
may help residents in institutions. It may reduce depressive symptoms
and improve overall behaviour. There may also be a beneficial effect on
emotional well-being and quality of life, as well as anxiety reduction.
Medications
Donepezil
No medications have been shown to prevent or cure dementia. Medications may be used to treat the behavioural and cognitive symptoms but have no effect on the underlying disease process.
Acetylcholinesterase inhibitors, such as donepezil, may be useful for Alzheimer disease and dementia in Parkinson's, DLB, or vascular dementia. The quality of the evidence however is poor and the benefit is small. No difference has been shown between the agents in this family. In a minority of people side effects include a slow heart rate and fainting.
As assessment for an underlying cause of the behavior is needed
before prescribing antipsychotic medication for symptoms of dementia.
Antipsychotic drugs should be used to treat dementia only if non-drug
therapies have not worked, and the person's actions threaten themselves
or others.
Aggressive behavior changes are sometimes the result of other solvable
problems, that could make treatment with antipsychotics unnecessary.
Because people with dementia can be aggressive, resistant to their
treatment, and otherwise disruptive, sometimes antipsychotic drugs are
considered as a therapy in response. These drugs have risky adverse effects, including increasing the person's chance of stroke and death. Given these adverse events and small benefit antipsychotics should be avoided whenever possible.
Generally, stopping antipsychotics for people with dementia does not
cause problems, even in those who have been on them a long time.
N-methyl-D-aspartate (NMDA) receptor blockers such as memantine may be of benefit but the evidence is less conclusive than for AChEIs.
Due to their differing mechanisms of action memantine and
acetylcholinesterase inhibitors can be used in combination however the
benefit is slight.
While depression is frequently associated with dementia, selective serotonin reuptake inhibitors (SSRIs) do not appear to affect outcomes. The SSRIs sertraline and citalopram have been demonstrated to reduce symptoms of agitation, compared to placebo.
The use of medications to alleviate sleep disturbances that
people with dementia often experience has not been well researched, even
for medications that are commonly prescribed. In 2012 the American Geriatrics Society recommended that benzodiazepines such as diazepam, and non-benzodiazepine hypnotics, be avoided for people with dementia due to the risks of increased cognitive impairment and falls. Additionally, there is little evidence for the effectiveness of benzodiazepines in this population. There is no clear evidence that melatonin or ramelteon improves sleep for people with dementia due to Alzheimer's disease. There is limited evidence that a low dose of trazodone may improve sleep, however more research is needed.
There is no solid evidence that folate or vitamin B12 improves outcomes in those with cognitive problems. Statins also have no benefit in dementia.
Medications for other health conditions may need to be managed
differently for a person who also has a diagnosis of dementia. It is
unclear if there is a link between blood pressure medication and
dementia. There is a possibility that people may experience an increase
in cardiovascular-related events if these medications are withdrawn.
The Medication Appropriateness Tool for Comorbid Health Conditions in Dementia
(MATCH-D) criteria can help identify ways that a diagnosis of dementia
changes medication management for other health conditions.
These criteria were developed because people with dementia live with an
average of five other chronic diseases, which are often managed with
medications.
Pain
As people age, they experience more health problems, and most health
problems associated with aging carry a substantial burden of pain;
therefore, between 25% and 50% of older adults experience persistent
pain. Seniors with dementia experience the same prevalence of conditions
likely to cause pain as seniors without dementia.
Pain is often overlooked in older adults and, when screened for, often
poorly assessed, especially among those with dementia since they become
incapable of informing others that they're in pain.
Beyond the issue of humane care, unrelieved pain has functional
implications. Persistent pain can lead to decreased ambulation,
depressed mood, sleep disturbances, impaired appetite, and exacerbation
of cognitive impairment, and pain-related interference with activity is a factor contributing to falls in the elderly.
Although persistent pain in the person with dementia is difficult
to communicate, diagnose, and treat, failure to address persistent pain
has profound functional, psychosocial, and quality of life
implications for this vulnerable population. Health professionals often
lack the skills and usually lack the time needed to recognize,
accurately assess, and adequately monitor pain in people with dementia.
Family members and friends can make a valuable contribution to the care
of a person with dementia by learning to recognize and assess their
pain. Educational resources (such as the Understand Pain and Dementia tutorial) and observational assessment tools are available.
Eating difficulties
Persons
with dementia may have difficulty eating. Whenever it is available as
an option, the recommended response to eating problems is having a
caretaker do assisted feeding for the person. A secondary option for people who cannot swallow effectively is to consider gastrostomyfeeding tube
placement as a way to give nutrition. However, in bringing person
comfort and keeping functional status while lowering risk of aspiration
pneumonia and death, assistance with oral feeding is at least as good as
tube feeding.
Tube-feeding is associated with agitation, increased use of physical
and chemical restraints, and worsening pressure ulcers. Tube feedings
may also cause fluid overload, diarrhea, abdominal pain, local
complications, less human interaction, and may increase the risk of
aspiration.
Benefits of this procedure in those with advanced dementia has not been shown.
The risks of using tube feeding include agitation, the person pulling
out the tube or otherwise being physically or chemically immobilized to
prevent them from doing this, or getting pressure ulcers. There is about a 1% fatality rate directly related to the procedure with a 3% major complication rate.
The percentage of people at the end of their life with dementia using
feeding tubes in the USA has dropped from 12% in 2000 to 6% as of 2014.
Aromatherapy and massage have unclear evidence. There have been studies on the efficacy and safety of cannabinoids in relieving behavioral and psychological symptoms of dementia.
Omega-3 fatty acid
supplements from plants or fish sources do not appear to benefit or
harm people with mild to moderate Alzheimer's disease. It is unclear if
taking omega-3 fatty acid supplements can improve other types of
dementia.
Palliative care
Given the progressive and terminal nature of dementia, palliative care
can be helpful to patients and their caregivers by helping both people
with the disorder and their caregivers understand what to expect, deal
with loss of physical and mental abilities, plan out a patient's wishes
and goals including surrogate decision making, and discuss wishes for or
against CPR and life support.
Because the decline can be rapid, and because most people prefer to
allow the person with dementia to make their own decisions, palliative
care involvement before the late stages of dementia is recommended.
Further research is required to determine the appropriate palliative
care interventions and how well they help people with advanced dementia.
The number of cases of dementia worldwide in 2010 was estimated at 35.6 million. In 2015, 46.8 million people live with dementia, with 58% living in low and middle income countries.
The prevalence of dementia differs in different world regions, ranging
from 4.7% in Central Europe to 8.7% in North Africa/Middle East; the
prevalence in other regions is estimated to be between 5.6 and 7.6% .
The number of people living with dementia is estimated to double every
20 years. In 2013 dementia resulted in about 1.7 million deaths, up from
0.8 million in 1990.
Around two thirds of individuals with dementia live in low- and
middle-income countries, where the sharpest increases in numbers are
predicted.
The annual incidence of dementia is over 9.9 million worldwide.
Almost half of the new cases of dementia occur in Asia, followed by
Europe (25%), the Americas (18%) and Africa (8%). The incidence of
dementia increases exponentially with increase in age, doubling with
every 6.3 year increase in age. Dementia affecting 5% of the population older than 65 and 20–40% of those older than 85. Rates are slightly higher in women than men at ages 65 and greater.
Dementia impacts not only the individuals with dementia, but also
their carers and the wider society. Among people aged 60 years and
over, dementia is ranked the 9th most burdensome condition according to
the 2010 Global Burden of Disease (GBD) estimates.The global costs of
dementia is around US$818 billion in 2015, a 35.4% increase from US$604
billion in 2010.
History
Until the end of the 19th century, dementia was a much broader
clinical concept. It included mental illness and any type of
psychosocial incapacity, including conditions that could be reversed. Dementia
at this time simply referred to anyone who had lost the ability to
reason, and was applied equally to psychosis of mental illness,
"organic" diseases like syphilis that destroy the brain, and to the dementia associated with old age, which was attributed to "hardening of the arteries".
Dementia has been referred to in medical texts since antiquity.
One of the earliest known allusions to dementia is attributed to the
7th-century BC Greek philosopherPythagoras,
who divided the human lifespan into six distinct phases, which were 0–6
(infancy), 7–21 (adolescence), 22–49 (young adulthood), 50–62 (middle
age), 63–79 (old age), and 80–death (advanced age). The last two he
described as the "senium", a period of mental and physical decay, and of
the final phase being where "the scene of mortal existence closes after
a great length of time that very fortunately, few of the human species
arrive at, where the mind is reduced to the imbecility of the first
epoch of infancy". In 550 BC, the Greek Athenian statesman and poet Solon
argued that the terms of a man's will might be invalidated if he
exhibited loss of judgement due to advanced age. Chinese medical texts
made allusions to the condition as well, and the characters for
"dementia" translate literally to "foolish old person".
Aristotle and Plato
from Ancient Greece spoke of the mental decay of advanced age, but
apparently simply viewed it as an inevitable process that affected all
old men, and which nothing could prevent. Plato stated that the elderly
were unsuited for any position of responsibility because, "There is not
much acumen of the mind that once carried them in their youth, those
characteristics one would call judgement, imagination, power of
reasoning, and memory. They see them gradually blunted by deterioration
and can hardly fulfill their function."
For comparison, the Roman statesman Cicero
held a view much more in line with modern-day medical wisdom that loss
of mental function was not inevitable in the elderly and "affected only
those old men who were weak-willed". He spoke of how those who remained
mentally active and eager to learn new things could stave off dementia.
However, Cicero's views on aging, although progressive, were largely
ignored in a world that would be dominated by Aristotle's medical
writings for centuries. Subsequent physicians during the time of Roman
Empire such as Galen and Celsus simply repeated the beliefs of Aristotle while adding few new contributions to medical knowledge.
Byzantine physicians sometimes wrote of dementia, and it is
recorded that at least seven emperors whose lifespans exceeded the age
of 70 displayed signs of cognitive decline. In Constantinople,
there existed special hospitals to house those diagnosed with dementia
or insanity, but these naturally did not apply to the emperors who were
above the law and whose health conditions could not be publicly
acknowledged.
Otherwise, little is recorded about dementia in Western medical
texts for nearly 1700 years. One of the few references to it was the
13th-century friar Roger Bacon, who viewed old age as divine punishment for original sin.
Although he repeated existing Aristotelian beliefs that dementia was
inevitable after a long enough lifespan, he did make the extremely
progressive assertion that the brain was the center of memory and
thought rather than the heart.
Poets, playwrights, and other writers however made frequent allusions to the loss of mental function in old age. Shakespeare notably mentions it in some of his plays including Hamlet and King Lear.
During the 19th century, doctors generally came to believe that dementia in the elderly was the result of cerebral atherosclerosis,
although opinions fluctuated between the idea that it was due to
blockage of the major arteries supplying the brain or small strokes
within the vessels of the cerebral cortex. This viewpoint remained
conventional medical wisdom through the first half of the 20th century,
but by the 1960s was increasingly challenged as the link between
neurodegenerative diseases and age-related cognitive decline was
established. By the 1970s, the medical community maintained that
vascular dementia was rarer than previously thought and Alzheimer's
disease caused the vast majority of mental impairments in old age. More
recently however, it is believed that dementia is often a mixture of
both conditions.
Much like other diseases associated with aging, dementia was
comparatively rare before the 20th century, due to the fact that it is
most common in people over 80, and such lifespans were uncommon in
preindustrial times. Conversely, syphilitic dementia was widespread in
the developed world until largely being eradicated by the use of
penicillin after WWII. With significant increases in life expectancy
following WWII, the number of people in developed countries over 65
started rapidly climbing. While elderly persons constituted an average
of 3–5% of the population prior to 1945, by 2010 it was common in many
countries to have 10–14% of people over 65 and in Germany and Japan,
this figure exceeded 20%. Public awareness of Alzheimer's Disease was
greatly increased in 1994 when former US president Ronald Reagan announced that he had been diagnosed with the condition.
In the more recent history of dementia, some hospitals in London
have found that using color, designs, pictures and lights have helped
dementia patients adjust to being at the hospital. These adjustments to
the layout of the dementia wings at these hospitals have helped patients
by preventing confusion.
Terminology
Dementia in the elderly has previously been called senile dementia or senility,
and viewed as a normal and somewhat inevitable aspect of growing old,
rather than as being caused by any specific diseases. The terminology,
"senile dementia" or "senility", is no longer recommended. In 1907, a specific organic dementia-causing process of early onset, called Alzheimer's disease,
was described. This was associated with particular microscopic changes
in the brain, but was seen as a rare disease of middle age because the
first person diagnosed with it was a 50-year-old woman.
By the period of 1913–20, schizophrenia had been well-defined in a way similar to today, and also the term dementia praecox
had been used to suggest the development of senile-type dementia at a
younger age. Eventually the two terms fused, so that until 1952
physicians used the terms dementia praecox (precocious dementia) and schizophrenia interchangeably. The term precocious dementia
for a mental illness suggested that a type of mental illness like
schizophrenia (including paranoia and decreased cognitive capacity)
could be expected to arrive normally in all persons with greater age. After about 1920, the beginning use of dementia
for what is now understood as schizophrenia and senile dementia helped
limit the word's meaning to "permanent, irreversible mental
deterioration". This began the change to the more recognizable use of
the term today.
In 1976, neurologist Robert Katzmann suggested a link between senile dementia and Alzheimer's disease.
Katzmann suggested that much of the senile dementia occurring (by
definition) after the age of 65, was pathologically identical with
Alzheimer's disease occurring before age 65 and therefore should not be
treated differently. He noted that "senile dementia" not being
considered a disease, but rather part of aging, was keeping millions of
aged patients experiencing what otherwise was identical with Alzheimer's
disease from being diagnosed as having a disease process, rather than
simply considered as aging normally.
Katzmann thus suggested that Alzheimer's disease, if taken to occur
over age 65, is actually common, not rare, and was the fourth- or
5th-leading cause of death, even though rarely reported on death
certificates in 1976.
This suggestion opened the view that dementia is never normal,
and must always be the result of a particular disease process, and is
not part of the normal healthy aging process, per se. The ensuing
debate led for a time to the proposed disease diagnosis of "senile
dementia of the Alzheimer's type" (SDAT) in persons over the age of 65,
with "Alzheimer's disease" diagnosed in persons younger than 65 who had
the same pathology. Eventually, however, it was agreed that the age
limit was artificial, and that Alzheimer's disease was the
appropriate term for persons with the particular brain pathology seen in
this disorder, regardless of the age of the person with the diagnosis. A
helpful finding was that although the incidence of Alzheimer's disease
increased with age (from 5–10% of 75-year-olds to as many as 40–50% of
90-year-olds), there was no age at which all persons developed it, so it
was not an inevitable consequence of aging, no matter how great an age a
person attained. Evidence of this is shown by numerous documented
supercentenarians (people living to 110 or more) that experienced no
serious cognitive impairment. There is some evidence that dementia is
most likely to develop between the ages of 80 and 84 and individuals who
pass that point without being affected have a lower chance of
developing it. Women account for a larger percentage of dementia cases
than men, although this can be attributed to their longer overall
lifespan and greater odds of attaining an age where the condition is
likely to occur.
Also, after 1952, mental illnesses like schizophrenia were removed from the category of organic brain syndromes,
and thus (by definition) removed from possible causes of "dementing
illnesses" (dementias). At the same, however, the traditional cause of
senile dementia – "hardening of the arteries" – now returned as a set of
dementias of vascular cause (small strokes). These were now termed multi-infarct dementias or vascular dementias.
In the 21st century, a number of other types of dementia have
been differentiated from Alzheimer's disease and vascular dementias
(these two being the most common types). This differentiation is on the
basis of pathological examination of brain tissues, by symptomatology,
and by different patterns of brain metabolic activity in nuclear medical
imaging tests such as SPECT and PETscans
of the brain. The various forms of dementia have differing prognoses
(expected outcome of illness), and also differing sets of epidemiologic
risk factors. The causal etiology of many of them, including Alzheimer's
disease, remains unclear, although many theories exist such as
accumulation of protein plaques as part of normal aging, inflammation
(either from bacterial pathogens or exposure to toxic chemicals),
inadequate blood sugar, and traumatic brain injury.
The societal cost of dementia is high, especially for family caregivers.
Many countries consider the care of people living with dementia a
national priority and invest in resources and education to better
inform health and social service workers, unpaid caregivers, relatives,
and members of the wider community. Several countries have national
plans or strategies.
In these national plans, there is recognition that people can live well
with dementia for a number of years, as long as there is the right
support and timely access to a diagnosis. The former British Prime
Minister David Cameron has described dementia as being a "national crisis", affecting 800,000 people in the United Kingdom.
In the United Kingdom, as with all mental disorders, where people
with dementia could potentially be a danger to themselves or others,
they can be detained under the Mental Health Act 1983
for the purposes of assessment, care and treatment. This is a last
resort, and usually avoided if the person has family or friends who can
ensure care.
Some hospitals in Britain are working to provide enriched and
friendlier care. To make the hospital wards calmer and less overwhelming
to the residents, the staff is replacing the usual nurses' station with
a collection of smaller desks, similar to a receptionist's. The
incorporation of bright lighting helps increase positive mood and allow
for the residents to see more easily.
Driving
with dementia could lead to severe injury or even death to self and
others. Doctors should advise appropriate testing on when to quit
driving. The United Kingdom DVLA
(Driver & Vehicle Licensing Agency) states that people with
dementia who specifically have poor short term memory, disorientation,
or lack of insight or judgment are not fit to drive, and in these
instances the DVLA must be informed so that the driving licence can be
revoked. They do, however, acknowledge low-severity cases and those with
an early diagnosis, and those drivers may be permitted to drive pending
medical reports.
Many support networks are available to people with dementia and
their families and caregivers. Several charitable organisations aim to
raise awareness and campaign for the rights of people living with
dementia. There is also support and guidance on assessing testamentary
capacity in people who have dementia.
In 2015, Atlantic Philanthropies announced a $177 million gift
aimed at understanding and reducing dementia. The recipient was Global
Brain Health Institute, a program co-led by the University of California, San Francisco and Trinity College Dublin.
This donation is the largest non-capital grant Atlantic has ever made,
and the biggest philanthropic donation in Irish history.
Dental health
There
is limited evidence that links poor oral health to cognitive decline.
However, failure to perform tooth brushing and gingival inflammation can
be used as dementia risk predictors.
Oral bacteria
The link between Alzheimer's and gum disease is oral bacteria.[166] In the oral cavity, a large number of bacterial species can be found including P. gingivalis, F. nucleatum, P. intermedia, and T. forsythia. Six oral trepomena spirochetes have also been examined in the brains of Alzheimer's patients.
Spirochetes are neurotropic in nature, meaning they act to destroy
nerve tissue and create inflammation. Inflammatory pathogens are an
indicator of Alzheimer's disease and bacteria related to gum disease
have been found in the brains of Alzheimer's disease individuals. The bacteria invade nerve tissue in the brain, increasing the permeability of the blood-brain barrier
and promoting the onset of Alzheimer's among the elderly population. It
has also been found that individuals with a plethora of tooth plaque
have a risk of cognitive decline. Poor oral hygiene can also have an adverse effect on speech and nutrition causing general and cognitive health decline.
Oral viruses
Herpes
simplex virus (HSV) has been found in over 70% of the 50 and older
population. HSV persists in the peripheral nervous system and can be
triggered by stress, illness or fatigue.
High proportions of viral-associated proteins in amyloid-containing
plaques or neurofibrillary tangles (NFTs) highly confirm the involvement
of HSV-1 in Alzheimer's disease pathology. NFTs are known as the
primary marker of Alzheimer's disease. HSV-1 produces the main
components of NFTs.
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