hypertension hypertension 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 usually does not cause symptoms. high blood pressure, however, is a major risk factor for stroke, coronary artery disease, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia. hypertension is a major cause of premature death worldwide. hypertensionother namesarterial hypertension, high blood pressureautomated arm blood pressure meter showing arterial hypertension (shown by a systolic blood pressure 158 mmhg, diastolic blood pressure 99 mmhg and heart rate of 80 beats per minute)specialtycardiologysymptomsnonecomplicationscoronary artery disease, stroke, heart failure, peripheral arterial disease, vision loss, chronic kidney disease, dementiacausesusually lifestyle and genetic factorsrisk factorslack of sleep, excess salt, excess body weight, smoking, alcohol, air pollutiondiagnostic methodresting blood pressure 130/80 or 140/90 mmhgtreatmentlifestyle changes, medicationsfrequency16–37% globallydeaths9.4 million / 18% (2010) 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, physical inactivity 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 classified 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 taken concurrently 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). signs and symptoms hypertension is rarely accompanied by symptoms, and its identification is usually through health 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 main article: secondary hypertension secondary hypertension is hypertension due to an identifiable cause, and may result in certain specific additional signs and symptoms. for example, as well as causing high blood pressure, cushing's syndrome frequently causes truncal obesity, glucose intolerance, moon face, a hump of fat behind the neck and shoulders (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 episodes of hypertension accompanied by headache, palpitations, pale appearance, and excessive sweating. hypertensive crisis main article: hypertensive crisis severely elevated blood pressure (equal to or greater than a systolic 180 or diastolic of 120) 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 main articles: gestational hypertension and pre-eclampsia 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 main article: essential 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 when associated with a western diet and lifestyle 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 and 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. 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 main article: 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 coffee, 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 main article: pathophysiology of hypertension 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