Hypertension

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

Hypertension
Other names	Arterial hypertension, high blood pressure
Automated arm blood pressure meter showing arterial hypertension (shown a systolic blood pressure 158 mmHg, diastolic blood pressure 99 mmHg and heart rate of 80 beats per minute)
Specialty	Cardiology
Symptoms	None
Complications	Coronary artery disease, stroke, heart failure, peripheral arterial disease, vision loss, chronic kidney disease, dementia
Causes	Usually lifestyle and genetic factors
Risk factors	Excess salt, excess body weight, smoking, alcohol
Diagnostic method	Resting blood pressure  130/80 or 140/90 mmHg
Treatment	Lifestyle changes, medications
Frequency	16–37% globally
Deaths	9.4 million / 18% (2010)

Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure typically does not cause symptoms. Long-term high blood pressure, however, is a major risk factor for coronary artery disease, stroke, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia.

High blood pressure is classified as primary (essential) hypertension or secondary hypertension. About 90–95% of cases are primary, defined as high blood pressure due to nonspecific lifestyle and genetic factors. Lifestyle factors that increase the risk include excess salt in the diet, excess body weight, smoking, and alcohol use. The remaining 5–10% of cases are categorized as secondary high blood pressure, defined as high blood pressure due to an identifiable cause, such as chronic kidney disease, narrowing of the kidney arteries, an endocrine disorder, or the use of birth control pills.

Blood pressure is expressed by two measurements, the systolic and diastolic pressures, which are the maximum and minimum pressures, respectively. For most adults, normal blood pressure at rest is within the range of 100–130 millimeters mercury (mmHg) systolic and 60–80 mmHg diastolic. For most adults, high blood pressure is present if the resting blood pressure is persistently at or above 130/80 or 140/90 mmHg. Different numbers apply to children. Ambulatory blood pressure monitoring over a 24-hour period appears more accurate than office-based blood pressure measurement.

Lifestyle changes and medications can lower blood pressure and decrease the risk of health complications. Lifestyle changes include weight loss, physical exercise, decreased salt intake, reducing alcohol intake, and a healthy diet. If lifestyle changes are not sufficient then blood pressure medications are used. Up to three medications can control blood pressure in 90% of people. The treatment of moderately high arterial blood pressure (defined as >160/100 mmHg) with medications is associated with an improved life expectancy. The effect of treatment of blood pressure between 130/80 mmHg and 160/100 mmHg is less clear, with some reviews finding benefit and others finding unclear benefit. High blood pressure affects between 16 and 37% of the population globally. In 2010 hypertension was believed to have been a factor in 18% of all deaths (9.4 million globally).

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Signs and symptoms

Hypertension is rarely accompanied by symptoms, and its identification is usually through screening, or when seeking healthcare for an unrelated problem. Some people with high blood pressure report headaches (particularly at the back of the head and in the morning), as well as lightheadedness, vertigo, tinnitus (buzzing or hissing in the ears), altered vision or fainting episodes. These symptoms, however, might be related to associated anxiety rather than the high blood pressure itself.

On physical examination, hypertension may be associated with the presence of changes in the optic fundus seen by ophthalmoscopy. The severity of the changes typical of hypertensive retinopathy is graded from I to IV; grades I and II may be difficult to differentiate. The severity of the retinopathy correlates roughly with the duration or the severity of the hypertension.

Secondary hypertension

Hypertension with certain specific additional signs and symptoms may suggest secondary hypertension, i.e. hypertension due to an identifiable cause. For example, Cushing's syndrome frequently causes truncal obesity, glucose intolerance, moon face, a hump of fat behind the neck/shoulder (referred to as a buffalo hump), and purple abdominal stretch marks. Hyperthyroidism frequently causes weight loss with increased appetite, fast heart rate, bulging eyes, and tremor. Renal artery stenosis (RAS) may be associated with a localized abdominal bruit to the left or right of the midline (unilateral RAS), or in both locations (bilateral RAS). Coarctation of the aorta frequently causes a decreased blood pressure in the lower extremities relative to the arms, or delayed or absent femoral arterial pulses. Pheochromocytoma may cause abrupt ("paroxysmal") episodes of hypertension accompanied by headache, palpitations, pale appearance, and excessive sweating.

Hypertensive crisis

Severely elevated blood pressure (equal to or greater than a systolic 180 or diastolic of 110) is referred to as a hypertensive crisis. Hypertensive crisis is categorized as either hypertensive urgency or hypertensive emergency, according to the absence or presence of end organ damage, respectively.

In hypertensive urgency, there is no evidence of end organ damage resulting from the elevated blood pressure. In these cases, oral medications are used to lower the BP gradually over 24 to 48 hours.

In hypertensive emergency, there is evidence of direct damage to one or more organs. The most affected organs include the brain, kidney, heart and lungs, producing symptoms which may include confusion, drowsiness, chest pain and breathlessness. In hypertensive emergency, the blood pressure must be reduced more rapidly to stop ongoing organ damage, however, there is a lack of randomized controlled trial evidence for this approach.

Pregnancy

Hypertension occurs in approximately 8–10% of pregnancies. Two blood pressure measurements six hours apart of greater than 140/90 mm Hg are diagnostic of hypertension in pregnancy. High blood pressure in pregnancy can be classified as pre-existing hypertension, gestational hypertension, or pre-eclampsia.

Pre-eclampsia is a serious condition of the second half of pregnancy and following delivery characterised by increased blood pressure and the presence of protein in the urine. It occurs in about 5% of pregnancies and is responsible for approximately 16% of all maternal deaths globally. Pre-eclampsia also doubles the risk of death of the baby around the time of birth. Usually there are no symptoms in pre-eclampsia and it is detected by routine screening. When symptoms of pre-eclampsia occur the most common are headache, visual disturbance (often "flashing lights"), vomiting, pain over the stomach, and swelling. Pre-eclampsia can occasionally progress to a life-threatening condition called eclampsia, which is a hypertensive emergency and has several serious complications including vision loss, brain swelling, seizures, kidney failure, pulmonary edema, and disseminated intravascular coagulation (a blood clotting disorder).

In contrast, gestational hypertension is defined as new-onset hypertension during pregnancy without protein in the urine.

Children

Failure to thrive, seizures, irritability, lack of energy, and difficulty in breathing can be associated with hypertension in newborns and young infants. In older infants and children, hypertension can cause headache, unexplained irritability, fatigue, failure to thrive, blurred vision, nosebleeds, and facial paralysis.

Causes

Primary hypertension

Hypertension results from a complex interaction of genes and environmental factors. Numerous common genetic variants with small effects on blood pressure have been identified as well as some rare genetic variants with large effects on blood pressure. Also, genome-wide association studies (GWAS) have identified 35 genetic loci related to blood pressure; 12 of these genetic loci influencing blood pressure were newly found. Sentinel SNP for each new genetic locus identified has shown an association with DNA methylation at multiple nearby CpG sites. These sentinel SNP are located within genes related to vascular smooth muscle and renal function. DNA methylation might affect in some way linking common genetic variation to multiple phenotypes even though mechanisms underlying these associations are not understood. Single variant test performed in this study for the 35 sentinel SNP (known and new) showed that genetic variants singly or in aggregate contribute to risk of clinical phenotypes related to high blood pressure.

Blood pressure rises with aging and the risk of becoming hypertensive in later life is significant. Several environmental factors influence blood pressure. High salt intake raises the blood pressure in salt sensitive individuals; lack of exercise, central obesity can play a role in individual cases. The possible roles of other factors such as caffeine consumption, and vitamin D deficiency are less clear. Insulin resistance, which is common in obesity and is a component of syndrome X (or the metabolic syndrome), also contributes to hypertension. One review suggests that sugar may play an important role in hypertension and salt is just an innocent bystander.

Events in early life, such as low birth weight, maternal smoking, and lack of breastfeeding may be risk factors for adult essential hypertension, although the mechanisms linking these exposures to adult hypertension remain unclear. An increased rate of high blood uric acid has been found in untreated people with hypertension in comparison with people with normal blood pressure, although it is uncertain whether the former plays a causal role or is subsidiary to poor kidney function. Average blood pressure may be higher in the winter than in the summer. Periodontal disease is also associated with high blood pressure.

Secondary hypertension

Secondary hypertension results from an identifiable cause. Kidney disease is the most common secondary cause of hypertension. Hypertension can also be caused by endocrine conditions, such as Cushing's syndrome, hyperthyroidism, hypothyroidism, acromegaly, Conn's syndrome or hyperaldosteronism, renal artery stenosis (from atherosclerosis or fibromuscular dysplasia), hyperparathyroidism, and pheochromocytoma. Other causes of secondary hypertension include obesity, sleep apnea, pregnancy, coarctation of the aorta, excessive eating of liquorice, excessive drinking of alcohol, certain prescription medicines, herbal remedies, and stimulants such as cocaine and methamphetamine. Arsenic exposure through drinking water has been shown to correlate with elevated blood pressure. Depression was also linked to hypertension. Loneliness is also a risk factor.

A 2018 review found that any alcohol increased blood pressure in males while over one or two drinks increased the risk in females.

Pathophysiology

Determinants of mean arterial pressure

 

Illustration depicting the effects of high blood pressure

 

In most people with established essential hypertension, increased resistance to blood flow (total peripheral resistance) accounts for the high pressure while cardiac output remains normal. There is evidence that some younger people with prehypertension or 'borderline hypertension' have high cardiac output, an elevated heart rate and normal peripheral resistance, termed hyperkinetic borderline hypertension. These individuals develop the typical features of established essential hypertension in later life as their cardiac output falls and peripheral resistance rises with age. Whether this pattern is typical of all people who ultimately develop hypertension is disputed. The increased peripheral resistance in established hypertension is mainly attributable to structural narrowing of small arteries and arterioles, although a reduction in the number or density of capillaries may also contribute.

It is not clear whether or not vasoconstriction of arteriolar blood vessels plays a role in hypertension. Hypertension is also associated with decreased peripheral venous compliance which may increase venous return, increase cardiac preload and, ultimately, cause diastolic dysfunction. 

Pulse pressure (the difference between systolic and diastolic blood pressure) is frequently increased in older people with hypertension. This can mean that systolic pressure is abnormally high, but diastolic pressure may be normal or low, a condition termed isolated systolic hypertension. The high pulse pressure in elderly people with hypertension or isolated systolic hypertension is explained by increased arterial stiffness, which typically accompanies aging and may be exacerbated by high blood pressure.

Many mechanisms have been proposed to account for the rise in peripheral resistance in hypertension. Most evidence implicates either disturbances in the kidneys' salt and water handling (particularly abnormalities in the intrarenal renin–angiotensin system) or abnormalities of the sympathetic nervous system. These mechanisms are not mutually exclusive and it is likely that both contribute to some extent in most cases of essential hypertension. It has also been suggested that endothelial dysfunction and vascular inflammation may also contribute to increased peripheral resistance and vascular damage in hypertension. Interleukin 17 has garnered interest for its role in increasing the production of several other immune system chemical signals thought to be involved in hypertension such as tumor necrosis factor alpha, interleukin 1, interleukin 6, and interleukin 8.

Excessive sodium or insufficient potassium in the diet leads to excessive intracellular sodium, which contracts vascular smooth muscle, restricting blood flow and so increases blood pressure.

Diagnosis

Hypertension is diagnosed on the basis of a persistently high resting blood pressure. The American Heart Association recommends at least three resting measurements on at least two separate health care visits. The UK National Institute for Health and Care Excellence recommends ambulatory blood pressure monitoring to confirm the diagnosis of hypertension if a clinic blood pressure is 140/90 mmHg or higher.

Measurement technique

For an accurate diagnosis of hypertension to be made, it is essential for proper blood pressure measurement technique to be used. Improper measurement of blood pressure is common and can change the blood pressure reading by up to 10 mmHg, which can lead to misdiagnosis and misclassification of hypertension. Correct blood pressure measurement technique involves several steps. Proper blood pressure measurement requires the person whose blood pressure is being measured to sit quietly for at least five minutes which is then followed by application of a properly fitted blood pressure cuff to a bare upper arm. The person should be seated with their back supported, feet flat on the floor, and with their legs uncrossed. The person whose blood pressure is being measured should avoid talking or moving during this process. The arm being measured should be supported on a flat surface at the level of the heart. Blood pressure measurement should be done in a quiet room so the medical professional checking the blood pressure can hear the Korotkoff sounds while listening to the brachial artery with a stethoscope for accurate blood pressure measurements. The blood pressure cuff should be deflated slowly (2-3 mmHg per second) while listening for the Korotkoff sounds. The bladder should be emptied before a person's blood pressure is measured since this can increase blood pressure by up to 15/10 mmHg. Multiple blood pressure readings (at least two) spaced 1–2 minutes apart should be obtained to ensure accuracy. Ambulatory blood pressure monitoring over 12 to 24 hours is the most accurate method to confirm the diagnosis. An exception to this is those with very high blood pressure readings especially when there is poor organ function.

With the availability of 24-hour ambulatory blood pressure monitors and home blood pressure machines, the importance of not wrongly diagnosing those who have white coat hypertension has led to a change in protocols. In the United Kingdom, current best practice is to follow up a single raised clinic reading with ambulatory measurement, or less ideally with home blood pressure monitoring over the course of 7 days. The United States Preventive Services Task Force also recommends getting measurements outside of the healthcare environment. Pseudohypertension in the elderly or noncompressibility artery syndrome may also require consideration. This condition is believed to be due to calcification of the arteries resulting in abnormally high blood pressure readings with a blood pressure cuff while intra arterial measurements of blood pressure are normal. Orthostatic hypertension is when blood pressure increases upon standing.

Other investigations

Typical tests performed

System	Tests
Kidney	Microscopic urinalysis, protein in the urine, BUN, creatinine
Endocrine	Serum sodium, potassium, calcium, TSH
Metabolic	Fasting blood glucose, HDL, LDL, total cholesterol, triglycerides
Other	Hematocrit, electrocardiogram, chest radiograph

Once the diagnosis of hypertension has been made, healthcare providers should attempt to identify the underlying cause based on risk factors and other symptoms, if present. Secondary hypertension is more common in preadolescent children, with most cases caused by kidney disease. Primary or essential hypertension is more common in adolescents and adults and has multiple risk factors, including obesity and a family history of hypertension. Laboratory tests can also be performed to identify possible causes of secondary hypertension, and to determine whether hypertension has caused damage to the heart, eyes, and kidneys. Additional tests for diabetes and high cholesterol levels are usually performed because these conditions are additional risk factors for the development of heart disease and may require treatment.

Initial assessment of the hypertensive people should include a complete history and physical examination. Serum creatinine is measured to assess for the presence of kidney disease, which can be either the cause or the result of hypertension. Serum creatinine alone may overestimate glomerular filtration rate and recent guidelines advocate the use of predictive equations such as the Modification of Diet in Renal Disease (MDRD) formula to estimate glomerular filtration rate (eGFR). eGFR can also provide a baseline measurement of kidney function that can be used to monitor for side effects of certain anti-hypertensive drugs on kidney function. Additionally, testing of urine samples for protein is used as a secondary indicator of kidney disease. Electrocardiogram (EKG/ECG) testing is done to check for evidence that the heart is under strain from high blood pressure. It may also show whether there is thickening of the heart muscle (left ventricular hypertrophy) or whether the heart has experienced a prior minor disturbance such as a silent heart attack. A chest X-ray or an echocardiogram may also be performed to look for signs of heart enlargement or damage to the heart.

Classification in adults

Classification in adults (Persons with systolic and diastolic in different categories are assigned to the higher category.)

Category	Systolic, mmHg	Diastolic, mmHg
Hypotension	< 90	< 60
Normal	90–119 90–129	60–79[7] 60–84
Prehypertension (high normal, elevated)	120–129 130–139	60–79 85–89
Stage 1 hypertension	130-139 140–159	80-89[7] 90–99
Stage 2 hypertension	>140 160–179	>90 100–109
Hypertensive crises	≥ 180	≥ 120
Isolated systolic hypertension	≥ 160	< 90 to 110
Isolated diastolic hypertension	< 140	≥ 90

Children

Hypertension occurs in around 0.2 to 3% of newborns; however, blood pressure is not measured routinely in healthy newborns. Hypertension is more common in high risk newborns. A variety of factors, such as gestational age, postconceptional age and birth weight needs to be taken into account when deciding if a blood pressure is normal in a newborn.

Hypertension defined as elevated blood pressure over several visits affects 1% to 5% of children and adolescents and is associated with long term risks of ill-health. Blood pressure rises with age in childhood and, in children, hypertension is defined as an average systolic or diastolic blood pressure on three or more occasions equal or higher than the 95th percentile appropriate for the sex, age and height of the child. High blood pressure must be confirmed on repeated visits however before characterizing a child as having hypertension. Prehypertension in children has been defined as average systolic or diastolic blood pressure that is greater than or equal to the 90th percentile, but less than the 95th percentile. In adolescents, it has been proposed that hypertension and pre-hypertension are diagnosed and classified using the same criteria as in adults.

The value of routine screening for hypertension in children over the age of 3 years is debated. In 2004 the National High Blood Pressure Education Program recommended that children aged 3 years and older have blood pressure measurement at least once at every health care visit and the National Heart, Lung, and Blood Institute and American Academy of Pediatrics made a similar recommendation. However, the American Academy of Family Physicians supports the view of the U.S. Preventive Services Task Force that the available evidence is insufficient to determine the balance of benefits and harms of screening for hypertension in children and adolescents who do not have symptoms.

Prevention

Much of the disease burden of high blood pressure is experienced by people who are not labeled as hypertensive. Consequently, population strategies are required to reduce the consequences of high blood pressure and reduce the need for antihypertensive medications. Lifestyle changes are recommended to lower blood pressure, before starting medications. The 2004 British Hypertension Society guidelines proposed lifestyle changes consistent with those outlined by the US National High BP Education Program in 2002 for the primary prevention of hypertension:

• maintain normal body weight for adults (e.g. body mass index 20–25 kg/m²)
• reduce dietary sodium intake to <100 chloride="" day="" g="" li="" mmol="" nbsp="" of="" or="" per="" sodium="">
• engage in regular aerobic physical activity such as brisk walking (≥30 min per day, most days of the week)
• limit alcohol consumption to no more than 3 units/day in men and no more than 2 units/day in women
• consume a diet rich in fruit and vegetables (e.g. at least five portions per day);

Effective lifestyle modification may lower blood pressure as much as an individual antihypertensive medication. Combinations of two or more lifestyle modifications can achieve even better results. There is considerable evidence that reducing dietary salt intake lowers blood pressure, but whether this translates into a reduction in mortality and cardiovascular disease remains uncertain. Estimated sodium intake ≥6g/day and <3g 3g="" a="" absence="" adverse="" and="" are="" associated="" association="" been="" below="" between="" both="" but="" cardiovascular="" class="mw-redirect" consequently="" controlled="" day="" death="" dietary="" disease="" esc="" from="" guidelines="" has="" high="" href="https://en.wikipedia.org/wiki/Periodontitis" hypertension.="" in="" intake="" is="" levels="" major="" mention="" observed="" of="" only="" or="" outcomes="" people="" questioned.="" randomized="" reducing="" results="" risk="" salt="" sodium="" the="" title="Periodontitis" trials="" wisdom="" with="">periodontitis

is associated with poor cardiovascular health status.

Management

According to one review published in 2003, reduction of the blood pressure by 5 mmHg can decrease the risk of stroke by 34%, of ischemic heart disease by 21%, and reduce the likelihood of dementia, heart failure, and mortality from cardiovascular disease.

Target blood pressure

Various expert groups have produced guidelines regarding how low the blood pressure target should be when a person is treated for hypertension. These groups recommend a target below the range 140–160 / 90–100 mmHg for the general population. Cochrane reviews recommend similar targets for subgroups such as people with diabetes and people with prior cardiovascular disease.

Many expert groups recommend a slightly higher target of 150/90 mmHg for those over somewhere between 60 and 80 years of age. The JNC-8 and American College of Physicians recommend the target of 150/90 mmHg for those over 60 years of age, but some experts within these groups disagree with this recommendation. Some expert groups have also recommended slightly lower targets in those with diabetes or chronic kidney disease with protein loss in the urine, but others recommend the same target as for the general population. The issue of what is the best target and whether targets should differ for high risk individuals is unresolved, although some experts propose more intensive blood pressure lowering than advocated in some guidelines.

For people who have never experienced cardiovascular disease who are at a 10-year risk of cardiovascular disease of less than 10%, the 2017 American Heart Association guidelines recommend medications if the systolic blood pressure is >140 mmHg or if the diastolic BP is >90 mmHg.^[7] For people who have experienced cardiovascular disease or those who are at a 10-year risk of cardiovascular disease of greater than 10%, it recommends medications if the systolic blood pressure is >130 mmHg or if the diastolic BP is >80 mmHg.

Lifestyle modifications

The first line of treatment for hypertension is lifestyle changes, including dietary changes, physical exercise, and weight loss. Though these have all been recommended in scientific advisories, a Cochrane systematic review found no evidence for effects of weight loss diets on death, long-term complications or adverse events in persons with hypertension. The review did find a decrease in blood pressure. Their potential effectiveness is similar to and at times exceeds a single medication. If hypertension is high enough to justify immediate use of medications, lifestyle changes are still recommended in conjunction with medication.

Dietary changes shown to reduce blood pressure include diets with low sodium, the DASH diet,^[118] vegetarian diets, and green tea consumption.

Increasing dietary potassium has a potential benefit for lowering the risk of hypertension. The 2015 Dietary Guidelines Advisory Committee (DGAC) stated that potassium is one of the shortfall nutrients which is under-consumed in the United States. However, people who take certain antihypertensive medications (such as ACE-inhibitors or ARBs) should not take potassium supplements or potassium-enriched salts due to the risk of high levels of potassium.

Physical exercise regimens which are shown to reduce blood pressure include isometric resistance exercise, aerobic exercise, resistance exercise, and device-guided breathing.

Stress reduction techniques such as biofeedback or transcendental meditation may be considered as an add-on to other treatments to reduce hypertension, but do not have evidence for preventing cardiovascular disease on their own. Self-monitoring and appointment reminders might support the use of other strategies to improve blood pressure control, but need further evaluation.

Medications

Several classes of medications, collectively referred to as antihypertensive medications, are available for treating hypertension.

First-line medications for hypertension include thiazide-diuretics, calcium channel blockers, angiotensin converting enzyme inhibitors (ACE inhibitors), and angiotensin receptor blockers (ARBs). These medications may be used alone or in combination (ACE inhibitors and ARBs are not recommended for use in combination); the latter option may serve to minimize counter-regulatory mechanisms that act to restore blood pressure values to pre-treatment levels. Most people require more than one medication to control their hypertension. Medications for blood pressure control should be implemented by a stepped care approach when target levels are not reached.

Previously beta-blockers such as atenolol were thought to have similar beneficial effects when used as first-line therapy for hypertension. However, a Cochrane review that included 13 trials found that the effects of beta-blockers are inferior to that of other antihypertensive medications in preventing cardiovascular disease.

Resistant hypertension

Resistant hypertension is defined as high blood pressure that remains above a target level, in spite of being prescribed three or more antihypertensive drugs simultaneously with different mechanisms of action. Failing to take prescribed medications as directed is an important cause of resistant hypertension. Resistant hypertension may also result from chronically high activity of the autonomic nervous system, an effect known as "neurogenic hypertension". Electrical therapies that stimulate the baroreflex are being studied as an option for lowering blood pressure in people in this situation.

Epidemiology

Rates of hypertension in adult men in 2014.

 

Disability-adjusted life year for hypertensive heart disease per 100,000 inhabitants in 2004.

no data   <110 div="">   110-220   220-330   330-440   440-550   550-660

660-770   770-880   880-990   990-1100   1100–1600   >1600

Adults

As of 2014, approximately one billion adults or ~22% of the population of the world have hypertension. It is slightly more frequent in men, in those of low socioeconomic status, and it becomes more common with age. It is common in high, medium, and low income countries. In 2004 rates of high blood pressure were highest in Africa, (30% for both sexes) and lowest in the Americas (18% for both sexes). Rates also vary markedly within regions with rates as low as 3.4% (men) and 6.8% (women) in rural India and as high as 68.9% (men) and 72.5% (women) in Poland. Rates in Africa were about 45% in 2016.

In Europe hypertension occurs in about 30-45% of people as of 2013. In 1995 it was estimated that 43 million people (24% of the population) in the United States had hypertension or were taking antihypertensive medication. By 2004 this had increased to 29% and further to 32% (76 million US adults) by 2017. In 2017, with the change in definitions for hypertension, 46% of people in the United States are affected. African-American adults in the United States have among the highest rates of hypertension in the world at 44%. It is also more common in Filipino Americans and less common in US whites and Mexican Americans.  Differences in hypertension rates are multifactorial and under study.

Children

Rates of high blood pressure in children and adolescents have increased in the last 20 years in the United States. Childhood hypertension, particularly in pre-adolescents, is more often secondary to an underlying disorder than in adults. Kidney disease is the most common secondary cause of hypertension in children and adolescents. Nevertheless, primary or essential hypertension accounts for most cases.

Outcomes

Diagram illustrating the main complications of persistent high blood pressure

 

Hypertension is the most important preventable risk factor for premature death worldwide. It increases the risk of ischemic heart disease, strokes, peripheral vascular disease, and other cardiovascular diseases, including heart failure, aortic aneurysms, diffuse atherosclerosis, chronic kidney disease, atrial fibrillation, and pulmonary embolism. Hypertension is also a risk factor for cognitive impairment and dementia. Other complications include hypertensive retinopathy and hypertensive nephropathy.

History

Image of veins from Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus

Measurement

Modern understanding of the cardiovascular system began with the work of physician William Harvey (1578–1657), who described the circulation of blood in his book "De motu cordis". The English clergyman Stephen Hales made the first published measurement of blood pressure in 1733. However, hypertension as a clinical entity came into its own with the invention of the cuff-based sphygmomanometer by Scipione Riva-Rocci in 1896. This allowed easy measurement of systolic pressure in the clinic. In 1905, Nikolai Korotkoff improved the technique by describing the Korotkoff sounds that are heard when the artery is ausculted with a stethoscope while the sphygmomanometer cuff is deflated. This permitted systolic and diastolic pressure to be measured.

Identification

The symptoms similar to symptoms of patients with hypertensive crisis are discussed in medieval Persian medical texts in the chapter of "fullness disease". The symptoms include headache, heaviness in the head, sluggish movements, general redness and warm to touch feel of the body, prominent, distended and tense vessels, fullness of the pulse, distension of the skin, coloured and dense urine, loss of appetite, weak eyesight, impairment of thinking, yawning, drowsiness, vascular rupture, and hemorrhagic stroke. Fullness disease was presumed to be due to an excessive amount of blood within the blood vessels. 

Descriptions of hypertension as a disease came among others from Thomas Young in 1808 and especially Richard Bright in 1836. The first report of elevated blood pressure in a person without evidence of kidney disease was made by Frederick Akbar Mahomed (1849–1884).

Treatment

Historically the treatment for what was called the "hard pulse disease" consisted in reducing the quantity of blood by bloodletting or the application of leeches. This was advocated by The Yellow Emperor of China, Cornelius Celsus, Galen, and Hippocrates. The therapeutic approach for the treatment of hard pulse disease included changes in lifestyle (staying away from anger and sexual intercourse) and dietary program for patients (avoiding the consumption of wine, meat, and pastries, reducing the volume of food in a meal, maintaining a low-energy diet and the dietary usage of spinach and vinegar). 

In the 19th and 20th centuries, before effective pharmacological treatment for hypertension became possible, three treatment modalities were used, all with numerous side-effects: strict sodium restriction (for example the rice diet), sympathectomy (surgical ablation of parts of the sympathetic nervous system), and pyrogen therapy (injection of substances that caused a fever, indirectly reducing blood pressure).

The first chemical for hypertension, sodium thiocyanate, was used in 1900 but had many side effects and was unpopular. Several other agents were developed after the Second World War, the most popular and reasonably effective of which were tetramethylammonium chloride, hexamethonium, hydralazine, and reserpine (derived from the medicinal plant Rauvolfia serpentina). None of these were well tolerated. A major breakthrough was achieved with the discovery of the first well-tolerated orally available agents. The first was chlorothiazide, the first thiazide diuretic and developed from the antibiotic sulfanilamide, which became available in 1958. Subsequently, beta blockers, calcium channel blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers, and renin inhibitors were developed as antihypertensive agents.

Society and culture

Awareness

Graph showing, prevalence of awareness, treatment and control of hypertension compared between the four studies of NHANES

 

The World Health Organization has identified hypertension, or high blood pressure, as the leading cause of cardiovascular mortality. The World Hypertension League (WHL), an umbrella organization of 85 national hypertension societies and leagues, recognized that more than 50% of the hypertensive population worldwide are unaware of their condition. To address this problem, the WHL initiated a global awareness campaign on hypertension in 2005 and dedicated May 17 of each year as World Hypertension Day (WHD). Over the past three years, more national societies have been engaging in WHD and have been innovative in their activities to get the message to the public. In 2007, there was record participation from 47 member countries of the WHL. During the week of WHD, all these countries – in partnership with their local governments, professional societies, nongovernmental organizations and private industries – promoted hypertension awareness among the public through several media and public rallies. Using mass media such as Internet and television, the message reached more than 250 million people. As the momentum picks up year after year, the WHL is confident that almost all the estimated 1.5 billion people affected by elevated blood pressure can be reached.

Economics

High blood pressure is the most common chronic medical problem prompting visits to primary health care providers in USA. The American Heart Association estimated the direct and indirect costs of high blood pressure in 2010 as $76.6 billion. In the US 80% of people with hypertension are aware of their condition, 71% take some antihypertensive medication, but only 48% of people aware that they have hypertension adequately control it. Adequate management of hypertension can be hampered by inadequacies in the diagnosis, treatment, or control of high blood pressure. Health care providers face many obstacles to achieving blood pressure control, including resistance to taking multiple medications to reach blood pressure goals. People also face the challenges of adhering to medicine schedules and making lifestyle changes. Nonetheless, the achievement of blood pressure goals is possible, and most importantly, lowering blood pressure significantly reduces the risk of death due to heart disease and stroke, the development of other debilitating conditions, and the cost associated with advanced medical care.

Research

A 2015 review of several studies found that restoring blood vitamin D levels by using supplements (more than 1,000 IU per day) reduced blood pressure in hypertensive individuals when they had existing vitamin D deficiency. The results also demonstrated a correlation of chronically low vitamin D levels with a higher chance of becoming hypertensive. Supplementation with vitamin D over 18 months in normotensive individuals with vitamin D deficiency did not significantly affect blood pressure.

There is tentative evidence that an increased calcium intake may help in preventing hypertension. However, more studies are needed to assess the optimal dose and the possible side effects.

Other animals

Cats

Hypertension in cats is indicated with a systolic blood pressure greater than 150 mm Hg, with amlodipine the usual first-line treatment.

Dogs

Normal blood pressure can differ substantially between breeds but hypertension in dogs is often diagnosed if systolic blood pressure is above 160 mm Hg particularly if this is associated with target organ damage. Inhibitors of the renin-angiotensin system and calcium channel blockers are often used to treat hypertension in dogs, although other drugs may be indicated for specific conditions causing high blood pressure.

Deliberative democracy

From Wikipedia, the free encyclopedia

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

 

Deliberative democracy or discursive democracy is a form of democracy in which deliberation is central to decision-making. It adopts elements of both consensus decision-making and majority rule. Deliberative democracy differs from traditional democratic theory in that authentic deliberation, not mere voting, is the primary source of legitimacy for the law.

While deliberative democracy is generally seen as some form of an amalgam of representative democracy and direct democracy, the actual relationship is usually open to dispute. Some practitioners and theorists use the term to encompass representative bodies whose members authentically and practically deliberate on legislation without unequal distributions of power, while others use the term exclusively to refer to decision-making directly by lay citizens, as in direct democracy.

The term "deliberative democracy" was originally coined by Joseph M. Bessette in his 1980 work Deliberative Democracy: The Majority Principle in Republican Government.

Overview

Deliberative democracy holds that, for a democratic decision to be legitimate, it must be preceded by authentic deliberation, not merely the aggregation of preferences that occurs in voting. Authentic deliberation is deliberation among decision-makers that is free from distortions of unequal political power, such as power a decision-maker obtained through economic wealth or the support of interest groups. If the decision-makers cannot reach consensus after authentically deliberating on a proposal, then they vote on the proposal using a form of majority rule.

The roots of deliberative democracy can be traced back to Aristotle and his notion of politics; however, the German philosopher Jürgen Habermas' work on communicative rationality and the public sphere is often identified as a major work in this area.

Deliberative democracy can be practiced by decision-makers in both representative democracies and direct democracies. In elitist deliberative democracy, principles of deliberative democracy apply to elite societal decision-making bodies, such as legislatures and courts; in populist deliberative democracy, principles of deliberative democracy apply to groups of lay citizens who are empowered to make decisions. One purpose of populist deliberative democracy can be to use deliberation among a group of lay citizens to distill a more authentic public opinion about societal issues but not directly create binding law; devices such as the deliberative opinion poll have been designed to achieve this goal. Another purpose of populist deliberative democracy can be to serve as a form of direct democracy, where deliberation among a group of lay citizens forms a "public will" and directly creates binding law. If political decisions are made by deliberation but not by the people themselves or their elected representatives, then there is no democratic element; this deliberative process is called elite deliberation. According to Fishkin, this process attempts to indirectly filter the mass public opinion because representatives are better equipped with the knowledge of the common good than ordinary citizens.

Characteristics

Fishkin's model of deliberation

James Fishkin, who has designed practical implementations of deliberative democracy for over 15 years in various countries, describes five characteristics essential for legitimate deliberation:

• Information: The extent to which participants are given access to reasonably accurate information that they believe to be relevant to the issue
• Substantive balance: The extent to which arguments offered by one side or from one perspective are answered by considerations offered by those who hold other perspectives
• Diversity: The extent to which the major position in the public are represented by participants in the discussion
• Conscientiousness: The extent to which participants sincerely weigh the merits of the arguments
• Equal consideration: The extent to which arguments offered by all participants are considered on the merits regardless of which participants offer them

In Fishkin's definition of deliberative democracy, lay citizens must participate in the decision-making process, thus making it a subtype of direct democracy.

James Fishkin and Robert Luskin suggest that deliberative discussion should be:

1. Informed (and thus informative). Arguments should be supported by appropriate and reasonably accurate factual claims.
2. Balanced. Arguments should be met by contrary arguments.
3. Conscientious. The participants should be willing to talk and listen, with civility and respect.
4. Substantive. Arguments should be considered sincerely on their merits, not on how they are made or by who is making them.
5. Comprehensive. All points of view held by significant portions of the population should receive attention.

Cohen's outline

Joshua Cohen, a student of John Rawls, outlined conditions that he thinks constitute the root principles of the theory of deliberative democracy, in the article "Deliberation and Democratic Legitimacy" in the 1989 book The Good Polity. He outlines five main features of deliberative democracy, which include:

1. An ongoing independent association with expected continuation.
2. The citizens in the democracy structure their institutions such that deliberation is the deciding factor in the creation of the institutions and the institutions allow deliberation to continue.
3. A commitment to the respect of a pluralism of values and aims within the polity.
4. The citizens consider deliberative procedure as the source of legitimacy, and prefer the causal history of legitimation for each law to be transparent and easily traceable to the deliberative process.
5. Each member recognizes and respects other members' deliberative capacity.

This can be construed as the idea that in the legislative process, we "owe" one another reasons for our proposals.

Cohen presents deliberative democracy as more than a theory of legitimacy, and forms a body of substantive rights around it based on achieving "ideal deliberation":

1. It is free in two ways:
   1. The participants consider themselves bound solely by the results and preconditions of the deliberation. They are free from any authority of prior norms or requirements.
   2. The participants suppose that they can act on the decision made; the deliberative process is a sufficient reason to comply with the decision reached.
2. Parties to deliberation are required to state reasons for their proposals, and proposals are accepted or rejected based on the reasons given, as the content of the very deliberation taking place.
3. Participants are equal in two ways:
   1. Formal: anyone can put forth proposals, criticize, and support measures. There is no substantive hierarchy.
   2. Substantive: The participants are not limited or bound by certain distributions of power, resources, or pre-existing norms. "The participants…do not regard themselves as bound by the existing system of rights, except insofar as that system establishes the framework of free deliberation among equals."
4. Deliberation aims at a rationally motivated consensus: it aims to find reasons acceptable to all who are committed to such a system of decision-making. When consensus or something near enough is not possible, majoritarian decision making is used.

In Democracy and Liberty, an essay published in 1998, Cohen reiterated many of these points, also emphasizing the concept of "reasonable pluralism" – the acceptance of different, incompatible worldviews and the importance of good faith deliberative efforts to ensure that as far as possible the holders of these views can live together on terms acceptable to all.

Gutmann and Thompson's model

Amy Gutmann and Dennis F. Thompson's definition captures the elements that are found in most conceptions of deliberative democracy. They define it as "a form of government in which free and equal citizens and their representatives justify decisions in a process in which they give one another reasons that are mutually acceptable and generally accessible, with the aim of reaching decisions that are binding on all at present but open to challenge in the future".

They state that deliberative democracy has four requirements, which refer to the kind of reasons that citizens and their representatives are expected to give to one another:

1. Reciprocal. The reasons should be acceptable to free and equal persons seeking fair terms of cooperation.
2. Accessible. The reasons must be given in public and the content must be understandable to the relevant audience.
3. Binding. The reason-giving process leads to a decision or law that is enforced for some period of time. The participants do not deliberate just for the sake of deliberation or for individual enlightenment.
4. Dynamic or Provisional. The participants must keep open the possibility of changing their minds, and continuing a reason-giving dialogue that can challenge previous decisions and laws.

Strengths and weaknesses

A claimed strength of deliberative democratic models is that they are more easily able to incorporate scientific opinion and base policy on outputs of ongoing research, because:

• Time is given for all participants to understand and discuss the science
• Scientific peer review, adversarial presentation of competing arguments, refereed journals, even betting markets, are also deliberative processes.
• The technology used to record dissent and document opinions opposed to the majority is also useful to notarize bets, predictions and claims.

According to proponents such as James Fearon, another strength of deliberative democratic models is that they tend, more than any other model, to generate ideal conditions of impartiality, rationality and knowledge of the relevant facts. The more these conditions are fulfilled, the greater the likelihood that the decisions reached are morally correct. Deliberative democracy takes on the role of an "epistemic democracy" in this way, as it thus has an epistemic value: it allows participants to deduce what is morally correct. This view has been prominently held by Carlos Nino.

Studies by James Fishkin and others have found that deliberative democracy tends to produce outcomes which are superior to those in other forms of democracy. Deliberative democracy produces less partisanship and more sympathy with opposing views; more respect for evidence-based reasoning rather than opinion; a greater commitment to the decisions taken by those involved; and a greater chance for widely shared consensus to emerge, thus promoting social cohesion between people from different backgrounds. Fishkin cites extensive empirical support for the increase in public spiritedness that is often caused by participation in deliberation, and says theoretical support can be traced back to foundational democratic thinkers such as John Stuart Mill and Alexis de Tocqueville. Former diplomat Carne Ross writes that in 2011 that the debates arising from deliberative democracy are also much more civil, collaborative, and evidence-based than the debates in traditional town hall meetings or in internet forums. For Ross, the key reason for this is that in deliberative democracy citizens are empowered by knowledge that their debates will have a measurable impact on society.

Efforts to promote public participation have been widely critiqued. There is particular concern regarding the potential capture of the public into the sphere of influence of governance stakeholders, leaving communities frustrated by public participation initiatives, marginalized and ignored.

A claimed failure of most theories of deliberative democracy is that they do not address the problems of voting. James Fishkin's 1991 work, "Democracy and Deliberation", introduced a way to apply the theory of deliberative democracy to real-world decision making, by way of what he calls the deliberative opinion poll. In the deliberative opinion poll, a statistically representative sample of the nation or a community is gathered to discuss an issue in conditions that further deliberation. The group is then polled, and the results of the poll and the actual deliberation can be used both as a recommending force and in certain circumstances, to replace a vote. Dozens of deliberative opinion polls have been conducted across the United States since his book was published.

The political philosopher Charles Blattberg has criticized deliberative democracy on four grounds: (i) the rules for deliberation that deliberative theorists affirm interfere with, rather than facilitate, good practical reasoning; (ii) deliberative democracy is ideologically biased in favor of liberalism as well as republican over parliamentary democratic systems; (iii) deliberative democrats assert a too-sharp division between just and rational deliberation on the one hand and self-interested and coercive bargaining or negotiation on the other; and (iv) deliberative democrats encourage an adversarial relationship between state and society, one that undermines solidarity between citizens.

A criticism of deliberation is that potentially it allows those most skilled in rhetoric to sway the decision in their favour. This criticism has been made since deliberative democracy first arose in Ancient Athens.

History

Consensus-based decision making similar to deliberative democracy is characteristic of the hunter gather band societies thought to predominate in pre-historical times. As some of these societies became more complex with developments like division of labour, community-based decision making was displaced by various forms of authoritarian rule. The first example of democracy arose in Greece as Athenian democracy during the sixth century BC. Athenian democracy was both deliberative and largely direct: some decisions were made by representatives but most were made by ″the people″ directly. Athenian democracy came to an end in 322BC. When democracy was revived as a political system about 2000 years later, decisions were made by representatives rather than directly by the people. In a sense, this revived version was deliberative from its beginnings; for example, in 1774 Edmund Burke made a famous speech where he called Great Britain's parliament a deliberative assembly. Similarly, the Founding Fathers of the United States considered deliberation an essential part of the government they created in the late 18th century.

The deliberative element of democracy was not widely studied by academics until the late 20th century. Although some of the seminal work was done in the 1970s and 80s, it was only in 1990 that deliberative democracy began to attract substantial attention from political scientists. According to Professor John Dryzek, early work on Deliberative Democracy was part of efforts to develop a theory of Democratic legitimacy. Theorists such as Carne Ross advocate deliberative democracy as a complete alternative to representative democracy. The more common view, held by contributors such as James Fishkin, is that direct deliberative democracy can be complementary to traditional representative democracy. Since 1994, hundreds of implementations of direct deliberative democracy have taken place throughout the world. For example, lay citizens have used deliberative democracy to determine local budget allocations in various cities and to undertake major public projects, such as the rebuilding of New Orleans after Hurricane Katrina.

Association with political movements

Call for the establishment of deliberative democracy on the Rally to Restore Sanity and/or Fear

 

Deliberative democracy recognizes a conflict of interest between the citizen participating, those affected or victimized by the process being undertaken, and the group-entity that organizes the decision. Thus it usually involves an extensive outreach effort to include marginalized, isolated, ignored groups in decisions, and to extensively document dissent, grounds for dissent, and future predictions of consequences of actions. It focuses as much on the process as the results. In this form it is a complete theory of civics. 

On the other hand, many practitioners of deliberative democracy attempt to be as neutral and open-ended as possible, inviting (or even randomly selecting) people who represent a wide range of views and providing them with balanced materials to guide their discussions. Examples include National Issues Forums, Choices for the 21st Century, study circles, deliberative opinion polls, the Citizens' Initiative Review, and the 21st-century town meetings convened by AmericaSpeaks, among others. In these cases, deliberative democracy is not connected to left-wing politics but is intended to create a conversation among people of different philosophies and beliefs.

In Canada, there have been two prominent applications of deliberative democratic models. In 2004, the British Columbia Citizens' Assembly on Electoral Reform convened a policy jury to consider alternatives to the first-past-the-post electoral systems. In 2007, the Ontario Citizens' Assembly on Electoral Reform convened to consider alternative electoral systems in that province. Similarly, three of Ontario's Local Health Integration Networks (LHIN) have referred their budget priorities to a policy jury for advice and refinement.

The Green Party of the United States refers to its particular proposals for grassroots democracy and electoral reform by this name. Although not always the case, participation in deliberation has often been found to shift participants opinions in favour of Green positions, and can even cause a favourable change of voting intention. For example, with Europolis 2009, at the time one of the largest deliberative assemblies ever held, which set out to assess the public's view on a wide range of issues and included representatives from all 27 EU member nations, the share of citizens intending to vote for the Greens increased from 8% to 18%.

Academic contributors

According to Professor Stephen Tierney, perhaps the earliest notable example of academic interest in the deliberative aspects of democracy occurred in John Rawls 1971 work A Theory of Justice.

Joseph M. Bessette coined the term "deliberative democracy" in his 1980 work "Deliberative Democracy: The Majority Principle in Republican Government", and went on to elaborate and defend the notion in "The Mild Voice of Reason" (1994). Others contributing to the notion of deliberative democracy include Carlos Nino, Jon Elster, Roberto Gargarella, John Gastil, Jürgen Habermas, David Held, Joshua Cohen, John Rawls, Amy Gutmann, Noëlle McAfee, John Dryzek, Rense Bos, James S. Fishkin, Jane Mansbridge, Jose Luis Marti, Dennis Thompson, Benny Hjern, Hal Koch, Seyla Benhabib, Ethan Leib, Charles Sabel, Jeffrey K. Tulis, David Estlund, Mariah Zeisberg, Jeffrey L. McNairn, Iris Marion Young and Robert B. Talisse.

Although political theorists took the lead in the study of deliberative democracy, political scientists have in recent years begun to investigate its processes. One of the main challenges currently is to discover more about the actual conditions under which the ideals of deliberative democracy are more or less likely to be realized.

Global Climate Observing System

From Wikipedia, the free encyclopedia

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

 

Global Climate Observing System

Abbreviation	GCOS
Formation	1992
Type	INGO
Region served	Worldwide
Official language	English
Parent organization	United Nations Framework Convention on Climate Change (UNFCCC)
Website	GCOS Official website

The Global Climate Observing System (GCOS) was established in 1992 as an outcome of the Second World Climate Conference, to ensure that the observations and information needed to address climate-related issues are obtained and made available to all potential users. The GCOS is co-sponsored by the World Meteorological Organization (WMO), the Intergovernmental Oceanographic Commission (IOC) of UNESCO, the United Nations Environment Programme (UNEP), and the International Council for Science (ICSU). In order to assess and monitor the adequacy of in-situ observation networks as well as satellite-based observing systems, GCOS regularly reports on the adequacy of the current climate observing system to the United Nations Framework Convention on Climate Change (UNFCCC), and thereby identifies the needs of the current climate observing system.

GCOS is a system that comprises the climate-relevant components of many contributing observing systems and networks. Its mission is to help ensure that these contributing systems, taken as a whole, provide the comprehensive information on the global climate system that is required by users, including individuals, national and international organizations, institutions and agencies. The programme promotes the sustained provision and availability of reliable physical, chemical and biological observations and data records for the total climate system - across the atmospheric, oceanic and terrestrial domains, including the hydrological cycle, the carbon cycle and the cryosphere.

Structure

The primary observing systems contributing to the GCOS are the WMO Integrated Global Observing System (WIGOS), the Global Cryosphere Watch (GCW), and the World Hydrological Cycle Observing System (WHYCOS), and the Intergovernmental Oceanographic Commission-led Global Ocean Observing System (GOOS). A number of other domain-based and cross-domain research and operational observing systems also provide important contributions and encompass both in-situ and satellite observations. GCOS is both supported by and supports the international scientific and technical community, and the World Climate Research Programme (WCRP) co-sponsors the expert panels set up by GCOS for the atmospheric, oceanic and terrestrial domains. The composite observing system designated by GCOS serves as the climate-observation component of the broader Global Earth Observation System of Systems (GEOSS), and at the same time a number of specific observing-system initiatives of GEOSS contribute to the GCOS.

Essential Climate Variables (ECVs)

GCOS has identified 50 Essential Climate Variables (ECVs) considered to be feasible for global climate observation and to have a high impact on the requirements of the UNFCCC and other stakeholders. There is a strong need for sustained observation of these ECVs, as the observations are needed for the generation and updating of global climate products and derived information. GCOS and its partners are developing ways of improving the generation and supply of data products relating to the ECVs.

Expert Panels

Three expert panels have been established by the GCOS Steering Committee to define the observations needed in each of the main global domains - Atmosphere, oceans, and land - to prepare specific programme elements and to make recommendations for implementation. GCOS is both supported by and supports the international scientific community, and therefore the three expert panels are co-sponsored by the World Climate Research Programme (WCRP). The Atmospheric, Ocean, and Terrestrial Observation Panel for Climate gather scientific and technical experts in the respective areas to generate inputs from these fields to the climate observing community. Those expert panels report to the GCOS Steering Committee, and have been established to define the observations needed in each of the main global domains to prepare scientific programme-elements and to make recommendations for implementation.

Atmospheric Observation Panel for Climate (AOPC)

AOPC was established in recognition of the need for specific scientific and technical input concerning atmospheric observations for climate. Its aim is to ensure the quality, long-term homogeneity and continuity of data needed. AOPC supports and is supported by the WMO Integrated Global Observing System (WIGOS).

Key activities of AOPC are: 

- Assessing the current state of the atmospheric component of the global observing system for climate and identify its gaps and adequacies;

- Securing the implementation of designated GCOS Networks and promote the establishment and enhancement of new and current systems to provide long-term and consistent data and information for Essential Climate Variables, such as earth radiation budget, surface radiation, greenhouse gases, water vapour, clouds and aerosols;

- Liaising with relevant research, operational and end-user bodies in order to determine and maintain the requirements for data to monitor, understand and predict the dynamical, physical and chemical state of the atmosphere and its interface on seasonal and multi-decadal time scales, on both global and regional levels;

- Promoting the transfer and accessibility to the user community, as well as the rehabilitation of historical observational and proxy climate data sets.

Ocean Observations Panel for Climate (OOPC)

OOPC, co-sponsored by GOOS, as well as GCOS and WCRP, is a scientific and technical advisory group charged with making recommendations for a sustained global ocean observing system for climate in support of the goals of its sponsors. This includes recommendations for phased implementation. The Panel also aids in the development of strategies for evaluation and evolution of the system and of its recommendations, and supports global ocean observing activities by interested parties through liaison and advocacy for the agreed observing plans.

OOPC recognizes the need for sustainable ocean observations, and the increased need to connect to societal issues in the coastal zone. OOPC's role has evolved to oversee the ocean component of the GCOS, and the physical variables for GOOS, while defining long-term observing requirements for climate research of WCRP.

Key activities of OOPC are:

- Providing advice on scientific and technical requirements to the Joint WMO-IOC Technical Commission on Oceanography and Marine Meteorology (JCOMM), which is responsible for the coordination and implementation of platform-based observing system components;

- Coordinate ocean observing networks that contribute to ocean ECVs by encouraging GOOS Regional Alliances (GRAs) and national commitments to global observing networks, and promoting common best practices and observing standards;

- Reviewing and prioritizing requirements for sustained ocean observations of the physical Essential Ocean Variables (EOVs), and ocean ECVs, to engage the broad stakeholder community, to assess the readiness of observing technologies and adequacy of present global key variable observations, and to provide a source of technical advice on the development of national coastal and ocean observing requirements and observing system implementation plans.

Terrestrial Observation Panel for Climate (TOPC)

TOPC was set up to develop a balanced and integrated system of-in situ and satellite observations of the terrestrial ecosystem. The Panel focuses on the identification of terrestrial observation requirements, assisting the establishment of observing networks for climate, providing guidance on observation standards and norms, facilitating access to climate data and information and its assimilation, and promoting climate studies and assessments.

Key activities of TOPC are:

- Identification of measurable terrestrial (biosphere, cryosphere, and hydrosphere) properties and key variables (ECVs) that control the physical, biological and chemical processes affecting climate, and are indicators of climate change; 

- Coordination of activities with other global observing system panels and task groups to ensure the consistency of requirements with the overall programmes;

- Assessing and monitoring the adequacy of terrestrial observing networks such as the Global Terrestrial Networks (GTNs), and promoting their integration and development to measure and exchange climate data and information;

- Identification of gaps in present observing systems and designs to ensure long-term monitoring of terrestrial ECVs.

Networks

One of the first tasks of the GCOS programme was to define a subset of the World Weather Watch (WWW) stations appropriate for basic climate monitoring. The subset of roughly 1000 baseline surface stations became the GCOS Surface Network (GSN), while a subset of 150 upper air stations was designated as the GCOS Upper-Air Network (GUAN). These were built on existing WMO classifications and became the initial baseline components of the atmospheric networks. Considerations for selection of GSN included spatial distribution, length and quality of record, long-term commitment, and degree of urbanization. Similar considerations were used for GUAN. Designation of these networks benefited both the GCOS and the National Meteorological and Hydrological Services (NMHS). For NMHSs, designation of a station as part of the global climate network helped sustain support for these sites with long-term records. The networks provided the foundation for the Regional Basic Climatological Network, which provides far greater spatial detail on the variability of climate.

Recognizing that a balance has to be struck between standards and completeness of ground-based measurement, the GCOS programme recognized a hierarchy of observational networks and systems, comprising comprehensive, baseline and reference networks based on assumptions of spatial sampling needs.

An example of a particularly successful step forward in implementing a global observing system for climate is the initiation of a reference network for upper-air observations - the GCOS Reference Upper-Air Network (GRUAN). The network is the prototype of a hybrid observing system, combining operational upper-air measurement sites with research sites and providing high-quality reference data for atmospheric profiles. GRUAN sites are undertaking high-quality atmospheric profile measurements that will help understand trends in upper-air ECVs, assist in investigating processes in the upper-troposphere and lower stratosphere, and provide data for calibrating satellite measurements and validating independent climate analyses and models. At GRUAN sites, the principles of quality, traceability and complete error characterization have been heeded, for at least part of the observing programme. The network is planned to grow over its initial size of 15 stations in coming years; introducing climate quality standards to a larger number of sites.