Lymphatic filariasis

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Lymphatic filariasis
Other names	Elephantiasis tropica, elephantiasis arabum
Bellevue Venus; Oscar G. Mason's portrait of a woman with elephantiasis.
Specialty	Infectious disease
Symptoms	None, severe swelling of the arms, legs, breasts, or genitals
Causes	Filarial worms spread by mosquitos
Diagnostic method	Microscopic examination of blood
Prevention	Bed nets, mass deworming
Medication	Albendazole with ivermectin or diethylcarbamazine
Frequency	38.5 million (2015)

Lymphatic filariasis is a human disease caused by parasitic worms known as filarial worms. Most cases of the disease have no symptoms. Some people, however, develop a syndrome called elephantiasis, which is marked by severe swelling in the arms, legs, breasts, or genitals. The skin may become thicker as well, and the condition may become painful. The changes to the body have the potential to harm the person's social and economic situation.

The worms are spread by the bites of infected mosquitoes. Three types of worms are known to cause the disease: Wuchereria bancrofti, Brugia malayi, and Brugia timori, with Wuchereria bancrofti being the most common. These worms damage the lymphatic system. The disease is diagnosed by microscopic examination of blood collected during the night. The blood is typically examined as a smear after being stained with Giemsa stain. Testing the blood for antibodies against the disease may also permit diagnosis. Other roundworms from the same family are responsible for river blindness.

Prevention can be achieved by treating entire groups in which the disease exists, known as mass deworming. This is done every year for about six years, in an effort to rid a population of the disease entirely. Medications used include antiparasitics such as albendazole with ivermectin, or albendazole with diethylcarbamazine. The medications do not kill the adult worms but prevent further spread of the disease until the worms die on their own. Efforts to prevent mosquito bites are also recommended, including reducing the number of mosquitoes and promoting the use of bed nets.

In 2015 about 38.5 million people were infected. About 950 million people are at risk of the disease in 54 countries. It is most common in tropical Africa and Asia. Lymphatic filariasis is classified as a neglected tropical disease and one of the four main worm infections. The impact of the disease results in economic losses of billions of dollars a year.

Signs and symptoms

The most spectacular symptom of lymphatic filariasis is elephantiasis, a stage 3 lymphedema with thickening of the skin and underlying tissues. This was the first mosquito-borne disease to be discovered. Elephantiasis results when the parasites lodge in the lymphatic system and cause blockages to the flow of lymph. Infections usually begin in childhood.

The skin condition the disease causes is called "elephantiasis tropica" (also known as "elephantiasis arabum").

Elephantiasis mainly affects the lower limbs and various species of filarial worms tend to affect different parts of the body: Wuchereria bancrofti can affect the arms, breasts, legs, scrotum, and vulva (causing hydrocele formation), while Brugia timori rarely affects the genitals. Those who develop the chronic stages of elephantiasis are usually amicrofilaraemic and often have adverse immunological reactions to the microfilariae as well as the adult worms.

The subcutaneous worms present with skin rashes, urticarial papules, and arthritis, as well as hyper- and hypopigmentation macules. The related Onchocerca volvulus manifests itself in the eyes, causing "river blindness" (onchocerciasis), one of the leading causes of blindness in the world.

Serous cavity filariasis presents with symptoms similar to subcutaneous filariasis; it may also be associated with ascites following the severe inflammatory reaction in the lymphatics.

Elephantiasis leads to marked swelling of the lower half of the body and thickening of the skin, making it look like that of an elephant, a term called "pachyderm".

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  Drawn from the collection at the National Museum of Health and Medicine and shows the effect of elephantiasis in an historic context. Anatomical items: Left Leg, Scrotum.

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  Elephantiasis of the legs due to filariasis. Luzon, Philippines.

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  Man with massive scrotal elephantiasis, Tanzania, early 20th century

Causes

Life cycle of Wuchereria bancrofti, a parasite that causes lymphatic filariasis

Elephantiasis occurs in the presence of microscopic, thread-like parasitic worms such as Wuchereria bancrofti (the most common), Brugia malayi, and Brugia timori, all of which are transmitted by bites from infected mosquitoes. It is a type of helminth infection. Three types of worm cause the disease and damage the lymphatic system.

The disease itself is a result of a complex interplay between several factors: the worm, the endosymbiotic Wolbachia bacteria within the worm, the host's immune response, and the numerous opportunistic infections and disorders that arise. The adult worms only live in the human lymphatic system. The parasite infects the lymph nodes and blocks the flow of lymph throughout the body; this results in chronic lymphedema, most often noted in the lower torso (typically in the legs and genitals).

Diagnosis

The standard method for diagnosing active infection is by finding the microfilariae via microscopic examination. This may be difficult, as in most parts of the world, microfilariae only circulate in the blood at night. For this reason, the blood has to be collected nocturnally. The blood sample is typically in the form of a thick smear and stained with Giemsa stain. Testing the blood serum for antibodies against the disease may also be used.

Prevention

The present objective of prevention is the eradication of lymphatic filariasis, which is achievable since the disease has no known animal reservoir.

The World Health Organization recommends mass deworming—treating entire groups of people who are at risk with a single annual dose of two medicines, namely albendazole in combination with either ivermectin or diethylcarbamazine citrate. With consistent treatment, since the disease needs a human host, the reduction of microfilariae means the disease will not be transmitted, the adult worms will die out, and the cycle will be broken. In sub-Saharan Africa, albendazole (donated by GlaxoSmithKline) is being used with ivermectin (donated by Merck & Co.) to treat the disease, whereas elsewhere in the world, albendazole is used with diethylcarbamazine. As of 2019 WHO recommends prevention with a combination of ivermectin, diethylcarbamazine, and albendazole in areas were onchocerciasis does not occur. Transmission of the infection can be broken when a single dose of these combined oral medicines is consistently maintained annually for a duration of four to six years. Using a combination of treatments better reduces the number of microfilariae in blood. Avoiding mosquito bites, such as by using insecticide-treated mosquito bed nets, also reduces the transmission of lymphatic filariasis.

The Carter Center's International Task Force for Disease Eradication declared lymphatic filariasis one of six potentially eradicable diseases. According to medical experts, the worldwide effort to eliminate lymphatic filariasis is on track to potentially succeed by 2020.

For similar-looking but causally unrelated podoconiosis, international awareness of the disease will have to increase before elimination is possible. In 2011, podoconiosis was added to the World Health Organization's Neglected Tropical Diseases list, which was an important milestone in raising global awareness of the condition. The efforts of the Global Programme to Eliminate LF are estimated to have prevented 6.6 million new filariasis cases from developing in children between 2000 and 2007, and to have stopped the progression of the disease in another 9.5 million people who had already contracted it. Dr. Mwele Malecela, who chairs the programme, said: "We are on track to accomplish our goal of elimination by 2020." In 2010, the WHO published a detailed progress report on the elimination campaign in which they assert that of the 81 countries with endemic LF, 53 have implemented mass drug administration, and 37 have completed five or more rounds in some areas, though urban areas remain problematic.

Treatment

Anthelmintic

Treatments for lymphatic filariasis differ depending on the geographic location of the area of the world in which the disease was acquired. In sub-Saharan Africa, albendazole is being used with ivermectin to treat the disease, whereas elsewhere in the world, albendazole is used with diethylcarbamazine. Geo-targeting treatments is part of a larger strategy to eventually eliminate lymphatic filariasis by 2020.

Antibiotics

The antibiotic doxycycline is also effective in treating lymphatic filariasis. Its drawbacks over anthelmintic drugs are that it requires 4 to 6 weeks of treatment, should not be used in young children and pregnant women, and is photosensitizing, which limits its use for mass prevention. The parasites responsible for elephantiasis have a population of endosymbiotic bacteria, Wolbachia, that live inside the worm. When the symbiotic bacteria of the adult worms are killed by the antibiotic, they no longer provide chemicals which the nematode larvae need to develop, which either kills the larvae or prevents their normal development. This permanently sterilizes the adult worms, which also die within 1 to 2 years instead of their normal 10 to 14-year lifespan.

Vaccine

A vaccine is not yet available, but in 2013 the University of Illinois College of Medicine was reporting 95% efficacy in testing against B. malayi in mice.

Supportive treatments

Additionally, surgical treatment may be helpful for issues related to scrotal elephantiasis and hydrocele. However, surgery is generally ineffective at correcting elephantiasis of the limbs.

Epidemiology

Disability-adjusted life year for lymphatic filariasis per 100,000 inhabitants

 

  no data

  less than 10

  10-50

  50-70

  70-80

  80-90

  90-100

  100-150

  150-200

  200-300

  300-400

  400-500

  more than 500

Elephantiasis caused by lymphatic filariasis is one of the most common causes of disability in the world. A 2012 report noted that lymphatic filariasis affected 120 million people and one billion people at risk for infection. About 40 million people were disfigured or incapacitated by the disease in 2015. It is considered endemic in tropical and subtropical regions of Africa, Asia, Central and South America, and Pacific Island nations.

In areas endemic for podoconiosis, prevalence can be 5% or higher. In communities where lymphatic filariasis is endemic, as many as 10% of women can be afflicted with swollen limbs, and 50% of men can suffer from mutilating genital symptoms.

Filariasis is considered endemic in 73 countries; 37 of these are in Africa.

• Togo is the first Africa country to have been validated by the World Health Organization (WHO) as having eliminated LF as public health problem
• In the Americas, it is present in Brazil, Costa Rica, the Dominican Republic, Guyana, Haiti, Suriname, and Trinidad and Tobago.
• In Asia, it is present in Bangladesh, Cambodia, India, Indonesia, Laos, Malaysia, Maldives, the Philippines, Sri Lanka, Thailand, Timor-Leste, and Vietnam.
• In the Middle East, it was present only in Yemen until August 2019 when the World Health Organization (WHO) validated Yemen as having eliminated LF as public health problem
• In the Pacific region, it is endemic in American Samoa, the Cook Islands, Fiji, French Polynesia, Micronesia, Niue, Papua New Guinea, Samoa, Tonga, Tuvalu, and Vanuatu.

In many of these countries, considerable progress has been made towards elimination of filariasis. In July 2017, the World Health Organization (WHO) announced that the disease had been eliminated in Tonga. Elimination of the disease has also occurred in Cambodia, the Cook Islands, Egypt, Kiribati, Maldives, Marshall Islands, Niue, Palau, Sri Lanka, Thailand, Vanuatu, Viet Nam and Wallis and Fortuna. This list is constantly updates and adds on the China and South Korea that were among the first countries to eliminate LF, according to the WHO.

History

A man in Japan is helped to carry his enlarged scrotum

Lymphatic filariasis is thought to have affected humans for about 4000 years. Artifacts from ancient Egypt (2000 BC) and the Nok civilization in West Africa (500 BC) show possible elephantiasis symptoms. The first clear reference to the disease occurs in ancient Greek literature, wherein scholars differentiated the often similar symptoms of lymphatic filariasis from those of leprosy, describing leprosy as elephantiasis graecorum and lymphatic filariasis as elephantiasis arabum.

The first documentation of symptoms occurred in the 16th century, when Jan Huyghen van Linschoten wrote about the disease during the exploration of Goa. Similar symptoms were reported by subsequent explorers in areas of Asia and Africa, though an understanding of the disease did not begin to develop until centuries later.

In 1866, Timothy Lewis, building on the work of Jean Nicolas Demarquay [de] and Otto Henry Wucherer, made the connection between microfilariae and elephantiasis, establishing the course of research that would ultimately explain the disease. In 1876, Joseph Bancroft discovered the adult form of the worm. In 1877, the lifecycle involving an arthropod vector was theorized by Patrick Manson, who proceeded to demonstrate the presence of the worms in mosquitoes. Manson incorrectly hypothesized that the disease was transmitted through skin contact with water in which the mosquitoes had laid eggs. In 1900, George Carmichael Low determined the actual transmission method by discovering the presence of the worm in the proboscis of the mosquito vector.

Many people in Malabar, Nayars as well as Brahmans and their wives — in fact about a quarter or a fifth of the total population, including the people of the lowest castes — have very large legs, swollen to a great size; and they die of this, and it is an ugly thing to see. They say that this is due to the water through which they go, because the country is marshy. This is called pericaes in the native language, and all the swelling is the same from the knees downward, and they have no pain, nor do they take any notice of this infirmity.

— Portuguese diplomat Tomé Pires, Suma Oriental, 1512–1515.

Research directions

Researchers at the University of Illinois at Chicago (UIC) have developed a novel vaccine for the prevention of lymphatic filariasis. This vaccine has been shown to elicit strong, protective immune responses in mouse models of lymphatic filariasis infection. The immune response elicited by this vaccine has been demonstrated to be protective against both W. bancrofti and B. malayi infection in the mouse model and may prove useful in the human.

On September 20, 2007, geneticists published the first draft of the complete genome (genetic content) of Brugia malayi, one of the roundworms which causes lymphatic filariasis. This project had been started in 1994 and by 2000, 80% of the genome had been determined. Determining the content of the genes might lead to the development of new drugs and vaccines.

Diseases of affluence

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Diseases_of_affluence 

Diseases of affluence, previously called diseases of rich people, is a term sometimes given to selected diseases and other health conditions which are commonly thought to be a result of increasing wealth in a society. Also referred to as the "Western disease" paradigm, these diseases are in contrast to so-called "diseases of poverty", which largely result from and contribute to human impoverishment. These diseases of affluence have vastly increased in prevalence since the end of World War II.

Examples of diseases of affluence include mostly chronic non-communicable diseases (NCDs) and other physical health conditions for which personal lifestyles and societal conditions associated with economic development are believed to be an important risk factor — such as type 2 diabetes, asthma, coronary heart disease, cerebrovascular disease, peripheral vascular disease, obesity, hypertension, cancer, alcoholism, gout, and some types of allergy. They may also be considered to include depression and other mental health conditions associated with increased social isolation and lower levels of psychological well being observed in many developed countries. Many of these conditions are interrelated, for example obesity is thought to be a partial cause of many other illnesses.

In contrast, the diseases of poverty have tended to be largely infectious diseases, or the result of poor living conditions. These include tuberculosis, malaria, and intestinal diseases. Increasingly, research is finding that diseases thought to be diseases of affluence also appear in large part in the poor. These diseases include obesity and cardiovascular disease and, coupled with infectious diseases, these further increase global health inequalities.

Diseases of affluence started to become more prevalent in developing countries as diseases of poverty decline, longevity increases, and lifestyles change. In 2008, nearly 80% of deaths due to NCDs — including heart disease, strokes, chronic lung diseases, cancers and diabetes — occurred in low- and middle-income countries.

Main instances

According to the World Health Organization (WHO), the top 10 causes of deaths in high income/affluent countries in 2016 were from:

1. Ischemic heart diseases
2. Stroke
3. Alzheimer disease and other dementia
4. Trachea, bronchus and lung cancer
5. Chronic obstructive pulmonary disease
6. Lower respiratory infections
7. Colon and rectum cancers
8. Diabetes
9. Kidney diseases
10. Breast cancer

Except for the lower respiratory infections, all of them are non-communicable diseases. In 2016 WHO reported 56.9 million deaths worldwide, and more than half (54%), were due to the top causes of death previously mentioned.

Causes

Factors associated with the increase of these conditions and illnesses appear to be things that are a direct result of technological advances. They include:

• Less strenuous physical exercise, often through increased use of motor vehicles
• Irregular exercise as a result of office jobs involving no physical labor.
• Easy accessibility in society to large amounts of low-cost food (relative to the much-lower caloric food availability in a subsistence economy)
  • More food generally, with much less physical exertion expended to obtain a moderate amount of food
  • Higher consumption of vegetable oils and high sugar-containing foods
  • Higher consumption of meat and dairy products
  • Higher consumption of refined flours and products made of such, like white bread or white noodles
  • More foods which are processed, cooked, and commercially provided (rather than seasonal, fresh foods prepared locally at the time of eating)
• Prolonged periods of little activity
• Greater use of alcohol and tobacco
• Longer lifespans
  • Reduced exposure to infectious agents throughout life (this can result in a more idle and inexperienced immune system, as compared to an individual who experienced relatively frequent exposure to certain pathogens in their time of life)
• Increased cleanliness. The hygiene hypothesis postulates that children of affluent families are now exposed to fewer antigens than has been normal in the past, giving rise to increased prevalence of allergy and autoimmune diseases.

Diabetes mellitus

Diabetes is a chronic metabolic disease characterized by increase blood glucose level. Type 2 diabetes is the most common form of diabetes. It is caused by resistance to insulin or the lack of production of insulin. It is seen most commonly in adults. Type 1 diabetes or juvenile diabetes affects mostly children. This condition is due to little or lack of insulin production from the pancreas.

According to WHO the prevalence of diabetes has quadrupled from 1980 to 422 million adults.The global prevalence of diabetes has increased from 4.7% in 1980 to 8.5% in 2014. Diabetes has been a major cause for blindness, kidney failure, heart attack, stroke and lower limb amputation.

Prevalence in countries of affluence

The Centers of Disease Control and Prevention (CDC) released a report in 2015 indicating that more than 100 million Americans have diabetes or pre-diabetes. Diabetes was the seventh leading cause of death in United States in 2015. In developed countries like the United States, the risk for diabetes is seen in people with low socioeconomic status (SES). Socioeconomic status is defined by the education and the income level of a person. The prevalence of diabetes varies by education level. Of those diagnosed with diabetes:12.6% of adults had less than a high school education, 9.5% had a high school education and 7.2% had more than high school education.

Differences in diabetes prevalence are seen in the population and ethnic groups in USA. Diabetes is more common in non-Hispanic whites who are less educated and have a lower income. It is also more common in less educated Hispanics. The highest prevalence of diabetes is seen in the southeast, southern and Appalachian portion of the United States. In the United States the prevalence of diabetes is increasing in children and adolescents. In 2015, 25 million people were diagnosed with diabetes, of which 193,000 were children. The total direct and indirect cost of diagnosed diabetes in US in 2012 was $245 billion.

In 2009, the Canadian Diabetes Association (CDA) estimated that diagnosed diabetes will increase from 1.3 million in 2000 to 2.5 million in 2010 and 3.7 million in 2020. Diabetes was the 7th leading cause of death in Canada in 2015. Like United States, diabetes in more prevalent in the low socioeconomic group of people in Canada.

According to the International Diabetes Federation, more than 58 million people are diagnosed with diabetes in the European Union Region (EUR), and this will go up to 66.7 million by 2045. Similar to other affluent countries like America and Canada, diabetes is more prevalent in the poorer parts of Europe like Central and Eastern Europe.

In Australia according to self-reported data, 1 in 7 adults or approximately 1.2 million people had diabetes in 2014–2015. People who were living in remote or socioeconomically disadvantaged areas were 4 times more likely to develop type 2 diabetes as compared to non-indigenous Australians. Australia incurred $20.8 million in direct costs towards hospitalization, medication, and out-patient treatment towards diabetes. In 2015, $1.2 billion were lost in Australia's Gross Domestic Product (GDP) due to diabetes.

In these countries of affluence, diabetes is prevalent in low socioeconomic groups of people as there is abundance of unhealthy food choices, high energy rich food, and decreased physical activity. More affluent people are typically more educated and have tools to counter unhealthy foods, such as access to healthy food, physical trainers, and parks and fitness centers.

Risk factors

Obesity and being overweight is one of the main risk factors of type 2 diabetes. Other risk factors include lack of physical activity, genetic predisposition, being over 45 years old, tobacco use, high blood pressure and high cholesterol. In United States, the prevalence of obesity was 39.8% in adults and 18.5% in children and adolescents in 2015–2016. In Australia in 2014–2015, 2 out 3 adults or 63% were overweight or obese. Also, 2 out of 3 adults did little or no exercise. According to the World Health Organization, Europe had the 2nd highest proportion of overweight or obese people in 2014 behind the Americas.

In developing countries

According to WHO the prevalence of diabetes is rising more in the middle and low income countries. Over the next 25 years, the number of people with diabetes in developing countries will increase by over 150%. Diabetes is typically seen in people above the retirement age in developed countries, but in developing countries people in the age of 35-64 are mostly affected. Although, diabetes is considered a disease of affluence affecting the developed countries, there is more loss of life and premature death among people with diabetes in the developing countries. Asia accounts for 60% of the world's diabetic population. In 1980 less than 1% of Chinese adults were affected by diabetes, but by 2008 the prevalence was 10%. It is predicted that by 2030 diabetes may affect 79.4 million people in India, 42.3 million people in China and 30.3 million in United States.

These changes are the result of developing nations having rapid economic development. This rapid economic development has caused a change in the lifestyle and food habits leading to over-nutrition, increased intake of fast food causing increase in weight, and insulin resistance. Compared to the west, obesity in Asia is low. India has very low prevalence of obesity, but a very high prevalence of diabetes suggesting that diabetes may occur at a lower BMI in Indians as compared to the Europeans. Smoking increases the risk for diabetes by 45%. In developing countries around 50–60% adult males are regular smokers, increasing their risk for diabetes. In developing countries, diabetes is more commonly seen in the more urbanized areas. The prevalence of diabetes in rural population is 1/4th that of urban population for countries like India, Bangladesh, Nepal, Bhutan and Sri Lanka.

Cardiovascular disease

Cardiovascular disease refers to a disease of the heart and blood vessels. Conditions and diseases associated with heart disease include: stroke, coronary heart disease, congenital heart disease, heart failure, peripheral vascular disease, and cardiomyopathy. Cardiovascular disease is known as the world's biggest killer. 17.5 million people die from it each year, which equals 31% of all deaths. Heart disease and stroke cause 80% of these deaths.

Risk factors

High blood pressure is the leading risk factor for cardiovascular disease and has contributed to 12% of the cardiovascular related deaths worldwide. Other significant risk factors for heart disease include high cholesterol and smoking. 47% of all Americans have one of these three risk factors. Lifestyle choices, such as poor diet and physical inactivity, and excessive alcohol use can also contribute to cardiovascular disease. Medical conditions, like diabetes and obesity can also be risk factors.

Prevalence in countries of affluence

In the United States, 610,000 people die every year from heart disease which is equal to 1 in 4 deaths. The leading cause of death for both men and women in the United States is heart disease. In Canada, heart disease is the second leading cause of death. In 2014, it was the cause of death for 51,000 people. In Australia, heart disease is also the leading cause of death. 29% of deaths in 2015, had an underlying cause of heart disease. Heart disease causes one in four premature deaths in the United Kingdom and in 2015 heart disease caused 26% of all deaths in that country.

People of lower socio-economic status are more likely to have cardiovascular disease than those who have a higher socio-economic status. This inequality gap has occurred in developed countries because people who have a lower socio-economic status often face many of the risk factors of tobacco and alcohol use, obesity as well as having a sedentary lifestyle. Further social and environmental factors such as poverty, pollution, family history, housing and employment contribute to this inequality gap and to risk of having a health condition caused by cardiovascular disease. The increasing inequality gap between the higher and lower income populations continues in countries such as Canada, despite the availability of health care for everyone.

Alzheimer's disease and other dementias

Dementia is a chronic syndrome which is characterized by deterioration in the thought process beyond what is expected from normal aging. It affects the persons memory, thinking, orientation, comprehension, behavior and ability to perform everyday activity. There are many different forms of dementia . Alzheimer is the most common form which contributes to 60–70% of the dementia cases. Different forms of dementia can co-exist. Young onset dementia which occurs in individuals before the age of 65 contributes to 9% of the total cases. It is the major cause of disability and dependency among old people.

Worldwide, there are 50 million people who are suffering from dementia and every year 10 million new cases are being reported. The total number of people with dementia is projected to reach 82 million by 2030 and 152 million in 2050.

Prevalence in countries of affluence

According to CDC, Alzheimer is the 6th leading cause of death in U.S adults and 5th leading cause of death in adults over the age of 65. In 2014, 5 million Americans above the age of 65 were diagnosed with Alzheimer. This number is predicted to triple by the year 2060 and reach up to 14 million. Dementia and Alzheimer has been shown to go unreported on death certificates, leading to under representation of the actual mortality caused by these diseases. Between 2000 and 2015, mortality due to cardiovascular diseases has decreased by 11%, where as death from Alzheimer has increased by 123%. 1 in 3 people over the age of 65 die from Alzheimer or other forms of dementia. Furthermore, 200,000 individuals have been affected by young onset dementia. In United States, Alzheimer affects more women than men. It is twice more common in African-Americans and Hispanics than in whites. As the number of older Americans increases rapidly, the number of new cases of Alzheimer will rise too.

East Asia has the most people living with dementia (9.8 million) followed by Western Europe (7.5 million), South Asia (5.1 million) and North America (4.8 million). In 2016, the prevalence of Alzheimer was 5.05% in Europe. Like in United States, it is more prevalent in women than in men. In the European Union, Finland has the highest mortality among both men and women due to dementia. In Canada, over half a million people are living with dementia. It is projected that by 2031 the number will go up by 66% to 937,000. Every year 25,000 new cases of dementia are diagnosed.

Dementia is the second leading cause of death in Australia. In 2016, it was the leading cause of deaths in females. In Australia 436,366 people are living with dementia in 2018. 3 in 10 people over the age of 85 and 1 in 10 people over the age of 65 have dementia. It is the single greatest cause of disability in older Australians. Rates of dementia are higher for indigenous people. In people from the northern territory and western Australia the prevalence of dementia is 26 times higher in the 45–69 year old group and about 20 times greater in 60–69 year old group.

Risk factors in countries of affluence

The risk factors for developing dementia or Alzheimer's include age, family history, genetic factors, environmental factors, brain injury, viral infections, neurotoxic chemicals, and various immunological and hormonal disorders.

A new research study has found an association between the affluence of a country, hygiene conditions and the prevalence of Alzheimer in their population. According to the Hygiene Hypothesis, affluent countries with more urbanized and industrialized areas have better hygiene, better sanitation, clean water and improved access to antibiotics. This reduces the exposure to the friendly bacteria, virus and other microorganisms that help stimulate our immune system. Decreased microbial exposure leads to immune system that is poorly developed, which exposes the brain to inflammation as is seen in Alzheimer's disease.

Countries like the UK and France that have access to clean drinking water, improved sanitation facilities and have a high GDP show a 9% increase in Alzheimer's disease as opposed to countries like Kenya and Cambodia. Also countries like UK and Australia, where three quarters of their population lives in urban areas, have a 10% higher Alzheimer's rate than in countries like Bangladesh and Nepal where less than one tenth of their population live in urban areas.

Alzheimer's risk changes with the environment. Individuals from the same ethnic background living in an area of low sanitation will have a lower risk as compared to the same individuals living in an area of high sanitation who will be exposed to a higher risk of developing Alzheimer's. An African-American in U.S. has a higher risk of developing Alzheimer's as compared to one living in Nigeria. Immigrant populations exhibit Alzheimer disease rates intermediate between their home country and adopted country. Moving from a country of high sanitation to a country of low sanitation reduces the risk associated with the disease.

Mental illness

People who face poverty have more risks related to having a mental illness and also do not have as much access to treatment. The stressful events that they face, unsafe living condition and poor physical health lead to cycle of poverty and mental illness that is seen all over the world. According to the World Health Organization 76–85% of people living in lower and middle income countries are not treated for their mental illness. For those in higher-income counties, 35–50% of people with mental illness do not receive treatment. It is estimated that 90% of deaths by suicide are caused by substance use disorders and mental illness in higher income countries. In lower to middle income countries, this number is lower.

Prevalence of mental illness

One in four people have experienced mental illness at one time in their lives, and approximately 450 million people in the world currently have a mental illness. Those who are impoverished live in conditions associated with a higher risk for mental illness and, to compound the issue, do not have as much access to treatment. Stress, unsafe living conditions, and poor physical health associated with lack of sufficient income lead to a cycle of poverty and mental illness that is observed worldwide. Of all countries, India, China, and the United States have the highest levels of anxiety, depression and schizophrenia, according to the WHO. The proportion of people with depression is between 2% to 6%; Greenland, Australia, and the United States have the highest rates of this disorder. Of these three, the U.S. is reported to have the greatest rate of depression. In the U.S., approximately one in five adults has a mental illness, or 44.7 million people. In 2016, it was estimated that 268 million people in the world had depression.

Anxiety disorders, such as generalized anxiety, Obsessive Compulsive Disorder, and Post Traumatic Stress Disorder affected 275 million people worldwide in 2016. The global proportion of people affected by anxiety disorders is between 2.5–6.5%. Australia, Brazil, Argentina, Iran, the United States, and a number of countries in Western Europe appear to have a higher prevalence of anxiety disorders.

Cancer

Cancer is a generic term for a large group of disease which is characterized by rapid creation of abnormal cells that grow beyond their usual boundaries. These cells can invade adjoining parts of the body and spread to other organs causing metastases, which is a major cause of death. According to WHO, Cancer is the second leading cause of death globally. One in six deaths worldwide are caused due to cancer, accounting to a total of 9.6 million deaths in 2018.Tracheal, bronchus, and lung cancer is the leading form of cancer deaths across most high and middle-income countries.

Prevalence in countries of affluence

In United States, 1,735,350 new cases of cancer will be diagnosed in 2018. Most common forms of cancer are cancer of the breast, lung, bronchus, prostate, colorectal cancer, melanoma of skin, Non-Hodgkin's lymphoma, renal cancer, thyroid cancer and liver cancer. Cancer mortality is higher among men than in women. African-Americans have the highest risk of mortality due to cancer. Cancer is also the leading cause of death in Australia. The most common cancers in Australia are prostate, breast, colorectal, melanoma and lung cancer. These account for 60% of the cancer cases diagnosed in Australia.

Europe contains only 1/8 of the world population, but has around one quarter of the global cancer cases, with 3.7 million new cases each year. Lung, breast, stomach, liver, colon are the most common cancers in Europe. The overall incidences among different cancers vary across countries.

About one in two Canadians will develop cancer in their lifetime, and one in four will die of the disease. In 2017, 206,200 new cases of cancer were diagnosed. Lung, colorectal, breast, and prostate cancer accounted for about half of all cancer diagnoses and deaths.

Risk factors

High prevalence of cancer in high-income countries is attributed to lifestyle factors like obesity, smoking, physical inactivity, diet and alcohol intake. Around 40% of the cancers can be prevented by modifying these factors.

Allergies/autoimmune diseases

The rate of allergies around the world has risen in industrialized nations over the past 50 years. A number of public health measures, such as sterilized milk, use of antibiotics and improved food production have contributed to a decrease in infections in developed countries. There is a proposed causal relationship, known as the "hygiene hypothesis" that indicates that there are more autoimmune disorders and allergies in developed countries with fewer infections. In developing countries, it is assumed that the rates of allergies are lower than developed countries. That assumption may not be accurate due to limited data on prevalence. Research has found an increase in asthma by 10% in countries such as Peru, Costa Rica, and Brazil.

Inequality in disease

From Wikipedia, the free encyclopedia

Social epidemiology focuses on the patterns in morbidity and mortality rates that emerge as a result of social characteristics. While an individual's lifestyle choices or family history may place him or her at an increased risk for developing certain illnesses, there are social inequalities in health that cannot be explained by individual factors. Variations in health outcomes in the United States are attributed to several social characteristics, such as gender, race, socioeconomic status, the environment, and educational attainment. Inequalities in any or all of these social categories can contribute to health disparities, with some groups placed at an increased risk for acquiring chronic diseases than others.

For example, cardiovascular disease is the leading cause of death in the United States, followed closely by cancer, with the fifth most deadly being diabetes. The general risk factors associated with these diseases include obesity and poor diet, tobacco and alcohol use, physical inactivity, and access to medical care and health information. Although it may seem that many of these risk factors arise solely from individual health choices, such a view neglects the structural patterns in the choices that individuals make. Consequently, a person's likelihood of developing heart disease, cancer, or diabetes is in part correlated with social factors. Among all racial groups, individuals who are impoverished or low income, have lower levels of educational attainment, and/or live in lower-income neighborhoods are all more likely to develop chronic diseases, such as heart disease, cancer, and diabetes.

Gender

In the United States and Europe, up until the 19th century, women tended to die at an earlier age than men. This was largely due to the risks involved in pregnancy and childbirth. However, in the late 19th century there was a shift in life expectancy and women started to live longer than men. Notably, this is partly explained by biological factors. For instance, there is a cross-cultural trend that male fetal mortality rates are higher than female fetal mortality rates. Additionally, estrogen decreases the risk of females acquiring heart disease by lowering the amount of cholesterol in the blood, while testosterone suppresses the immune system in males and puts them at risk for acquiring serious illnesses. However, biological differences do not fully account for the large gender gap in the health outcomes of men and women. Social factors play a large role in gender disparities in health.

One of the main factors that contributes to the decreased life expectancy of males is their propensity to engage in risk-taking behaviors. Some commonly cited examples include heavy drinking, illicit drug use, violence, drunk driving, not wearing helmets, and smoking. These behaviors contribute to injuries that may lead to premature death in males. In particular, the effect of risk-taking behavior on health is especially visible in the case of smoking. As smoking rates have fallen in the United States overall, less men engage in this behavior and the life expectancy gap between men and women has slightly decreased as a result.

The behaviour of men and women also vary in regards to diet and exercise, leading to differential health outcomes . On average, men exercise more than women, but their diet is less nutritious. Consequently, men are more likely to be overweight, while women are at greater risk for obesity. Exposure to violence is another social factor that has an influence on health. In general, women have a higher likelihood of experiencing sexual and intimate partner violence, while men are twice as likely to die from suicide or homicide.

Markedly, the impact of gender on health becomes especially salient in different socioeconomic contexts. In the United States, there is a large economic gender inequality with many economically disadvantaged women occupying much fewer positions of power than men. According to the Panel Study of Income Dynamics, "among adults with the strongest attachment to the labor force, only 9.6% of women earned more than $50,000 annually, compared with 44.5% of men."  This gendered economic inequality is partly responsible for the gender-health paradox: the general trend that women live longer than men, but experience a greater degree of non-life-threatening chronic illnesses over the course of a lifetime. A low socioeconomic status in women contributes to feelings of a lack of personal control over the events in their lives, increased stress, and low self-esteem. Perpetual states of stress inflict damage on the bodies and minds of women, placing them at risk for physical ailments, such as heart disease and arthritis, as well mental health disorders, such as depression.

Another significant social factor is that men and women deal with their illnesses in different ways. Women generally have strong support networks and are able to rely on others for emotional support, with the potential to improve their states of health. In contrast, men are less likely to have strong support networks, they have fewer doctor visits, and often cope with their illnesses on their own. Also, men and women express pain in different ways. Researchers have observed that women openly express feelings of pain, while men are more reserved in this regard and prefer to appear tough even when they experience severe mental or physical suffering. This finding suggests that this is due to socialization processes. Women are taught to be submissive and emotional, while men are taught to be strong, powerful figures that do not show their emotions. The social stigma associated with expressions of pain prevents men from admitting their suffering to others, making it more difficult to overcome the pain.

Moreover, neighborhood effects have a greater influence on women than men. For instance, research findings suggest that women living in impoverished neighborhoods are more likely to experience obesity, while this effect is not as strong for men. The physical environment also generally impacts a woman's self-rated health. This effect can be explained by the fact that women spend more time at home than their male counterparts, as a result of higher unemployment rates, and therefore may be more exposed to negative environmental characteristics that take a toll on their health.

Finally, gender effects also vary with race, ethnicity, and nativity status. Notably, Christy Erving conducted a study in which she examined the gender differences in the health profiles of African Americans and Caribbean blacks (immigrants and U.S. born). One of the findings from this research is that on average, African American women report lower self-rated measures of health, worse physical health, and were more likely to experience severe chronic illnesses than men. This finding contradicts the gender-health paradox in the sense that researchers would expect morbidity rates to be higher for women, but less of the illnesses that they acquire should be debilitating. In contrast, the opposite trend is observed for U.S. born Caribbean blacks, with men more likely to experience chronic, life-threatening illnesses than women. The health outcomes of Caribbean black immigrants are somewhere in-between the health outcomes of U.S. born Caribbean blacks and African Americans, wherein the females have a lower value of self-reported health but experience equal rates of life-threatening, chronic disease as men. This data illustrates that even within one racial category, there can be stark gender differences in health on the basis of social differences within the groups that compose the race.

Race

Studies have shown that individuals that are racially and ethnically stigmatized, not just in the U.S., but globally as well, experience health issues such as mental and physical illness, and in some cases even death, in higher rates than the average individual. There has been some controversy around "race" being a determinant of disease and health issues, since there are unmeasured forms of background history that are potential factors in this research. Geographical origins and the types of environments individual races were exposed to are huge contributes to the health of a certain race, especially when the environment that they are in now is not the same as the one their race originates from geographically.

Along with these factors, physical, psychological, social, and chemical environments are all included and accounted for. Including exposure over the course of one's life and through generations, and biological adaptation to these environmental exposures, including gene expression. An example of this is a study of hypertension between black people and whites. West Africans and people of West African descent levels of hypertension increased when they moved from Africa to the United States. Their levels of hypertension were twice as high as the levels of black people that were in Africa. While whites in the United States even had higher rates of hypertension than Black people in Africa, the black people in the United States rates of hypertension were higher than some predominately white populations in Europe. Again, this proves that when a race is taken out of their original geographic environment, they are more prone to disease and illness, because their genetic make-up was made for a specific type of environment.

Transitioning from the environmental aspect of race and disease, there is a direct correlation between race and socioeconomic status which contributes to racial disparities in health. When it comes to death rates from heart disease, the rate is about twice as high for black men vs. white men. Now, death rates from heart disease are lower for both black and white women compared to their male counterparts, but the patterns of racial disparities and education disparities for women are similar to that of the men. Death from heart disease is about three times as higher for black women than white women. For both black men and women, racial differences in deaths from heart disease at every level of education is evident, with the racial gap being larger at the higher levels of education than at the lowest levels. There are a number of reasons why race matters in terms of health after socioeconomic status has been accounted for. For one, health is affected by adversity early on in one's life, such as traumatic stress, poverty, and abuse. These factors affect the physical and mental health of an individual. As we know, most of the people living in poverty in the United States are minorities, specifically African Americans, so unfortunately there is no surprise that they are the individuals with so many health issues.

Continuously, race is relevant to health issues, because of the non-equivalence of socioeconomic status indicators across racial groups. At the same level of education, minorities (black people and non-white Hispanic people) receive less income than their Anglo-white counterparts, as well as have less wealth and purchasing power. Namely, one of the biggest reasons that race matters in terms of health is due to racism. Both personal and institutionalized racism are very prominent in today's society, maybe not as blunt and easy to notice in comparison to the past, but it still exists. Certain residential segregation by race, such as redlining, has created very distinct racial differences in terms of education, employment, and opportunities. Opportunities such as access to good healthcare/medical care. Institutional and cultural racism can even harm minorities health through stereotypes and prejudices, which contributes to socioeconomic mobility and can reduce and limit resources and opportunities required for a healthy lifestyle.

Socioeconomic status is only one part of racial disparities in health that reflect larger social inequalities in society. Racism is a system that combines with, and sometimes changes, socioeconomic status to influence health, and race still matters for health when socioeconomic status is considered.

Socioeconomic status

Socioeconomic status is a multidimensional classification, often defined using an individual's income and level of education. Other related metrics can round out this definition; for example, in a 2006 study by authors Cox, McKevitt, Rudd and Wolfe, further categories included "occupation, home and goods ownership, and area-based deprivation indices" in their determination of status.

Income inequality has risen rapidly in the United States, pushing greater amounts of the population into positions of lower socioeconomic status. A study published in 1993 examined Americans who had passed away between May and August 1960, and paired the mortality information with income, education and occupation data for each person. The work found an inverse correlation between socioeconomic status and mortality rate, as well as an increasing strength of this pattern and its reflection of the growth of income inequality in the United States.

These findings, although concerned with total mortality of any cause, reflect a similar relationship between socioeconomic status and disease incidence or death in the United States. Disease composes a very significant portion of U.S. mortality; as of May 2017, 6 out of 7 of the leading causes of death in America are non-communicable diseases, including heart disease, cancer, lower respiratory diseases, and cerebrovascular diseases (stroke). Indeed, these diseases have been seen to disproportionately affect the socioeconomically disadvantaged, albeit to different degrees and with differing magnitude. Mortality rates associated with cardiovascular disease (CVD), including coronary heart disease (CHD) and stroke, were assessed for individuals across areas of differing income and income inequality. The authors found that the mortality rates for each of the three respective diseases were greater by a factor of 1.36, 1.26, and 1.60, in areas of higher inequality compared to lower inequality areas of similar income. Across areas of differing income and constant income inequality, the rate of death due to CVD, CHD and stroke was increased by a factor of 1.27, 1.15, and 1.33 in the lower income areas. These trends across two measures of variation in socioeconomic status reflect the complexity and depth of the relationship between disease and economic standing. The authors are careful to state that while these patterns exist, they are not sufficiently described as related by cause and effect. While correlating, health and status have arisen in the U.S. from interrelated forces that may intricately accumulate or negate one another due to specific historical contexts.

As this lack of cause and effect simplicity indicates, exactly where disease-related health inequality arises is murky, and multiple factors likely contribute. Important to an examination of disease and health in the context of a complicated classification like socioeconomic status is the degree to which these measures are tied up with mechanisms that are dependent upon the individual, and those that are regionally variant. In the aforementioned 2006 study, the authors define individualized factors within three categories, "material (eg, income, possessions, environment), behavioural (eg, diet, smoking, exercise) and psychosocial (eg, perceived inequality, stress)", and provide two categories for external, regionally varying factors, "environmental influences (such as provision of and access to services) and psychosocial influences (such as social support)." The interactive and compounding nature of these forces can shape and be shaped by socioeconomic status, presenting a challenge to researchers to tease apart the intersecting factors of health and status. In the 2006 study, authors examined the specific drivers of the correlation between stroke occurrence and socioeconomic status. Identifying more nuanced and interlocking factors, they cited risk behaviors, early life influences, and access to care as tied to socioeconomic status and thus health inequality.

Inequality in disease is intricately tangled up with stratification of social class and economic status in the United States. Correlations, often disease-dependent, between health and socioeconomic attainment have been demonstrated in numerous studies for numerous diseases. The causes of these correlations are interlocking and often related to factors varying between regions and individuals, and design of future studies concerning inequality in disease require careful thought to the multifaceted driving mechanisms of social inequality.

Environment

The neighbourhood and areas people live in, as well as their occupation, make up the environment in which they exist. People living in poverty stricken neighborhoods are at a greater risk for heart disease, possibly because the supermarkets in their area do not sell healthy foods and there is increased availability of stores selling alcohol and tobacco than in more affluent parts of town. People living in rural areas are also more susceptible to heart disease, as well. An agriculturally based diet rich in fat and cholesterol, combined with an isolated environment in which there is limited access to health care and ways to distribute information probably creates a pattern in which people living in rural environments have higher levels of heart disease. Occupational cancer is one way in which the environment one works in can increase their rate of disease. Employees exposed to smoke, asbestos, diesel fumes, paint, and chemicals in factories can develop cancer from their workplace. All of these jobs tend to be low-paying and typically held by low income individuals. The decreased amount of healthy food in stores located in low-income areas also contributes to the increased rates of diabetes for persons living in those neighborhoods. One of the best examples of this can be seen by observing the city of Jacksonville, Florida.

Food deserts in urban Jacksonville

In Jacksonville, Florida it is hard to find groceries stores around the area because it is surrounded by fats, sugar, and high in cholesterol markets. In Duval County, there are 177,000 food insecure individuals such as children, families,senior citizens, and veterans that do not know when they will have a chance to have another meal again. Nearly 60 percent of the food that is consumed in Duval County is processed. To combat this, agencies helped distribute food and they averaged 12.3 million meals over eight counties in Northern Florida. In Duval alone, 3.5 million meals were handed out to families. The image below shows all of the hunger-relief partner agencies located within Jacksonville's food deserts that get food from Feeding Northeast Florida. In all Feeding Northeast Florida provided 4.2 million pounds of food to agencies in food deserts. These numbers were stats recorded in 2016.

Water pollution

Just like Flint Jacksonville had a water crisis and found 23 different chemicals in their water supply. It was so bad that Jacksonville was labeled top 10 in worst water in the nation. They stood at number 10 because of the 23 different chemicals. The chemicals that were most found in the water in high volumes were trihalomethanes, which is made up of four different cleaning by products such as chloroform. Trihalomethanes are confirmed to be carcinogenic. Throughout the five year testing period, unsafe levels of trihalomethanes were found during the 32 months of testing, and levels that are considered illegal by the EPA were found in 12 of those months. In one of the testing periods the trihalomethanes were found at twice the EPA legal limit. Other chemicals such as lead and arsenic that can cause health problems to people, were also found in the drinking water.

Another way that water pollution is damaged is from nutrient overload. Nutrient overload is caused by manure and fertilizers, storm water runoff, and wastewater treatment plants. This occurs in a lot of Florida rivers and the rivers are contained with blue green algae that feed on all those nutrients. All the waste that is dumped into the rivers gets fed on by other plants and animals that release toxins in the area, which makes everything surrounded by it a deadly toxin as well. The toxins that are dumped into the rivers can cause discoloration in the rivers to make a dark blue and green color. By looking at the river most people can tell how dangerous and harmful it is to be around it. If the water were to somehow get into water companies people can receive serious harm from drinking and bathing with this water.

Education

Education level is a great predictor of socioeconomic status. On average, individuals with a bachelors, associates, and high school degrees will annually earn 64.5, 50, and 41 thousand dollars respectively. This means that the average bachelor's degree earner will receive approximately $1,000,000 more over their working life than an individual with only a high school degree. Furthermore, as authors Montez, Hummer, and Hayward explained, "In 2012, unemployment was 12.4 percent among adults who did not graduate high school, compared to 8.3 percent among adults with a high school diploma and 4.5 percent among college graduates." Because the relationship between socioeconomic status and the prevalence of disease has already been well established, education is indirectly responsible for an increased prevalence of disease among the impoverished.

More directly, educational attainment is a great predictor of how likely an individual is to engage in risky, possibly disease causing, behaviors. In terms of smoking, which directly correlates to an increased risk for diseases like lung cancer, education is an important determining factor in the likelihood of an individual to smoke. As of 2009-10, 35 percent of adults who did not graduate high school were smokers, compared to 30 percent of high school graduates and just 13 percent of college graduates. High school graduates also smoked more packs, on average, each year than smokers who had graduated from college. Furthermore, individuals with a high school degree or less were 30% less likely to abstain from smoking for at least 3 months during their time as a regular smoker Other studies have found that binge drinking is higher among those with college degrees, implying that binge drinking is a habitat developed by many during the college years.

Unhealthy dietary habits can also directly lead to diseases such as heart disease, hypertension, and type-2 diabetes. One of the leading causes of unhealthy eating habits is a lack of access to grocery stores, creating so called "food deserts." Studies have found that immediate access to a grocery store (within 1.5 mile radius) was 1.4 times less likely in areas where only 27%, or less, of the population was college graduates. The negative effects of these food deserts are exacerbated by the fact that impoverished neighborhoods also had an oversupply of liquor store, fast food restaurants, and convenience stores.

One significant risk for sexually active individuals is that of sexually transmitted diseases and infections. While studies have found that the correlation between education and carrying these is relatively low on average (and even less so for certain subsets such as Black women), there is a strong correlation between education and other risky sexual behaviors. Those with only a high school degree or less were significantly more likely to engage in risky practices such as early sexual initiation, sexual activity with those who use "shooting" street drugs such as heroin, and even prostitution. In addition, those with less education were also less likely to practice some safe sex practices such as condom use.

Studies have also found that adults with higher educational achievement were more likely to lead healthier lives. Intake of key nutrients such as Vitamins A and C, potassium, and calcium was positively correlated with education level. This is a critical statistic because those nutrients, such as Vitamin C, are critical in helping the body fight diseases and infections. There was also a correlation between education and exercise habits. A 2010 study found that while 85% of college graduates stated they exercised in the last month, only 68% of high school graduates and 61% of non-high school graduates said the same. Because exercise is so crucial to preventing diseases like hypertension and type 2 diabetes, this stark distinction between exercise habitats can have significant effects. By 2011, 15% of high school (or less) graduates had diabetes, compared to just 7% of college graduates.

Arguably the best way of seeing the true effects of education in the inequality of disease is to examine mortality levels, as Heart Disease, Cancer, and Lower Respiratory Diseases are the top three killers, respectively, of Americans every year. By age 25, if an individual does not have at least a high school degree, they will die an average of 9 years earlier than an otherwise similar college graduate. A different national study found that individuals with only bachelor's degrees were 26% more likely to die in the next 5 years than individuals of the same age with professional degrees such as a master's. Even more stark, Americans without a high school degree were almost twice as likely to die than those with a professional degree in the study's 5 year follow-up period.

Population health

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Population_health 

 

Income inequality and mortality in 282 metropolitan areas of the United States. Mortality is correlated with both income and inequality.

Population health has been defined as "the health outcomes of a group of individuals, including the distribution of such outcomes within the group". It is an approach to health that aims to improve the health of an entire human population. It has been described as consisting of three components. These are "health outcomes, patterns of health determinants, and policies and interventions".

A priority considered important in achieving the aim of population health is to reduce health inequities or disparities among different population groups due to, among other factors, the social determinants of health (SDOH). The SDOH include all the factors (social, environmental, cultural and physical) that the different populations are born into, grow up and function with throughout their lifetimes which potentially have a measurable impact on the health of human populations. The population health concept represents a change in the focus from the individual-level, characteristic of most mainstream medicine. It also seeks to complement the classic efforts of public health agencies by addressing a broader range of factors shown to impact the health of different populations. The World Health Organization's Commission on Social Determinants of Health, reported in 2008, that the SDOH factors were responsible for the bulk of diseases and injuries and these were the major causes of health inequities in all countries. In the US, SDOH were estimated to account for 70% of avoidable mortality.

From a population health perspective, health has been defined not simply as a state free from disease but as "the capacity of people to adapt to, respond to, or control life's challenges and changes". The World Health Organization (WHO) defined health in its broader sense in 1946 as "a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity."

Healthy People 2020

Healthy People 2020 is a web site sponsored by the US Department of Health and Human Services, representing the cumulative effort of 34 years of interest by the Surgeon General's office and others. It identifies 42 topics considered social determinants of health and approximately 1200 specific goals considered to improve population health. It provides links to the current research available for selected topics and identifies and supports the need for community involvement considered essential to address these problems realistically.

Economic inequality

Recently, human role has been encouraged by the influence of population growth there has been increasing interest from epidemiologists on the subject of economic inequality and its relation to the health of populations. There is a very robust correlation between socioeconomic status and health. This correlation suggests that it is not only the poor who tend to be sick when everyone else is healthy, heart disease, ulcers, type 2 diabetes, rheumatoid arthritis, certain types of cancer, and premature aging. Despite the reality of the SES Gradient, there is debate as to its cause. A number of researchers (A. Leigh, C. Jencks, A. Clarkwest—see also Russell Sage working papers) see a definite link between economic status and mortality due to the greater economic resources of the better-off, but they find little correlation due to social status differences.

Other researchers such as Richard G. Wilkinson, J. Lynch, and G.A. Kaplan have found that socioeconomic status strongly affects health even when controlling for economic resources and access to health care. Most famous for linking social status with health are the Whitehall studies—a series of studies conducted on civil servants in London. The studies found that, despite the fact that all civil servants in England have the same access to health care, there was a strong correlation between social status and health. The studies found that this relationship stayed strong even when controlling for health-affecting habits such as exercise, smoking and drinking. Furthermore, it has been noted that no amount of medical attention will help decrease the likelihood of someone getting type 1 diabetes or rheumatoid arthritis—yet both are more common among populations with lower socioeconomic status. Lastly, it has been found that amongst the wealthiest quarter of countries on earth (a set stretching from Luxembourg to Slovakia) there is no relation between a country's wealth and general population health—suggesting that past a certain level, absolute levels of wealth have little impact on population health, but relative levels within a country do. The concept of psychosocial stress attempts to explain how psychosocial phenomenon such as status and social stratification can lead to the many diseases associated with the SES gradient. Higher levels of economic inequality tend to intensify social hierarchies and generally degrades the quality of social relations—leading to greater levels of stress and stress related diseases. Richard Wilkinson found this to be true not only for the poorest members of society, but also for the wealthiest. Economic inequality is bad for everyone's health. Inequality does not only affect the health of human populations. David H. Abbott at the Wisconsin National Primate Research Center found that among many primate species, less egalitarian social structures correlated with higher levels of stress hormones among socially subordinate individuals. Research by Robert Sapolsky of Stanford University provides similar findings.

Research

There is well-documented variation in health outcomes and health care utilization & costs by geographic variation in the U.S., down to the level of Hospital Referral Regions (defined as a regional health care market, which may cross state boundaries, of which there are 306 in the U.S.). There is ongoing debate as to the relative contributions of race, gender, poverty, education level and place to these variations. The Office of Epidemiology of the Maternal and Child Health Bureau recommends using an analytic approach (Fixed Effects or hybrid Fixed Effects) to research on health disparities to reduce the confounding effects of neighborhood (geographic) variables on the outcomes.

Critiques

Population health has been subject to ongoing critiques and its assumptions

Subfields

Family planning

Family planning programs (including contraceptives, sexuality education, and promotion of safe sex) play a major role in population health. Family planning is one of the most highly cost-effective interventions in medicine. Family planning saves lives and money by reducing unintended pregnancy and the transmission of sexually transmitted infections.

For example, the United States Agency for International Development lists as benefits of its international family planning program:

• "Protecting the health of women by reducing high-risk pregnancies"
• "Protecting the health of children by allowing sufficient time between pregnancies"
• "Fighting HIV/AIDS through providing information, counseling, and access to male and female condoms"
• "Reducing abortions"
• "Supporting women's rights and opportunities for education, employment, and full participation in society"
• "Protecting the environment by stabilizing population growth"

Mental health

There are three main kinds of population-based approaches to mental health: health care system interventions; public health practice interventions; and social, economic, and environmental policy interventions. Health care system interventions are mediated by the health care system and hospital leaders. Examples of these interventions include enhancing the efficacy of clinical mental health services, providing consultations and training for community partners, and sharing aggregate health data to inform policy, practice, and planning for public mental health. Public health practice interventions are mediated by public health department officials. These interventions include advocating for policy changes, initiating public service announcements to reduce the stigma of mental illness, and conducting outreach to increase the accessibility of community mental health resources. Elected officials and administrative policy makers implement social, economic, and environmental policy interventions. These can include reducing financial and housing insecurity, changing the built environment to increase urban green space and decrease nighttime noise pollution, and reducing structural stigma directed at those with mental illness.

Population health management (PHM)

One method to improve population health is population health management (PHM), which has been defined as "the technical field of endeavor which utilizes a variety of individual, organizational and cultural interventions to help improve the morbidity patterns (i.e., the illness and injury burden) and the health care use behavior of defined populations". PHM is distinguished from disease management by including more chronic conditions and diseases, by use of "a single point of contact and coordination", and by "predictive modeling across multiple clinical conditions". PHM is considered broader than disease management in that it also includes "intensive care management for individuals at the highest level of risk" and "personal health management... for those at lower levels of predicted health risk". Many PHM-related articles are published in Population Health Management, the official journal of DMAA: The Care Continuum Alliance.

The following road map has been suggested for helping healthcare organizations navigate the path toward implementing effective population health management:

• Establish precise patient registries
• Determine patient-provider attribution
• Define precise numerators in the patient registries
• Monitor and measure clinical and cost metrics
• Adhere to basic clinical practice guidelines
• Engage in risk-management outreach
• Acquire external data
• Communicate with patients
• Educate patients and engage with them
• Establish and adhere to complex clinical practice guidelines
• Coordinate effectively between care team and patient
• Track specific outcomes

Healthcare reform and population health

Healthcare reform is driving change to traditional hospital reimbursement models. Prior to the introduction of the Patient Protection and Affordable Care Act (PPACA), hospitals were reimbursed based on the volume of procedures through fee-for-service models. Under the PPACA, reimbursement models are shifting from volume to value. New reimbursement models are built around pay for performance, a value-based reimbursement approach, which places financial incentives around patient outcomes and has drastically changed the way US hospitals must conduct business to remain financially viable. In addition to focusing on improving patient experience of care and reducing costs, hospitals must also focus on improving the health of populations (IHI Triple Aim).

As participation in value-based reimbursement models such as accountable care organizations (ACOs) increases, these initiatives will help drive population health. Within the ACO model, hospitals have to meet specific quality benchmarks, focus on prevention, and carefully manage patients with chronic diseases. Providers get paid more for keeping their patients healthy and out of the hospital. Studies have shown that inpatient admission rates have dropped over the past ten years in communities that were early adopters of the ACO model and implemented population health measures to treat "less sick" patients in the outpatient setting. A study conducted in the Chicago area showed a decline in inpatient utilization rates across all age groups, which was an average of a 5% overall drop in inpatient admissions.

Hospitals are finding it financially advantageous to focus on population health management and keeping people in the community well. The goal of population health management is to improve patient outcomes and increase health capital. Other goals include preventing disease, closing care gaps, and cost savings for providers. In the last few years, more effort has been directed towards developing telehealth services, community-based clinics in areas with high proportion of residents using the emergency department as primary care, and patient care coordinator roles to coordinate healthcare services across the care continuum.

Health can be considered a capital good; health capital is part of human capital as defined by the Grossman model. Health can be considered both an investment good and consumption good. Factors such as obesity and smoking have negative effects on health capital, while education, wage rate, and age may also impact health capital. When people are healthier through preventative care, they have the potential to live a longer and healthier life, work more and participate in the economy, and produce more based on the work done. These factors all have the potential to increase earnings. Some states, like New York, have implemented statewide initiatives to address population health. In New York state there are 11 such programs. One example is the Mohawk Valley Population Health Improvement Program (http://www.mvphip.org/). These programs work to address the needs of the people in their region, as well as assist their local community based organizations and social services to gather data, address health disparities, and explore evidence-based interventions that will ultimately lead to better health for everyone.