Hypertension
Hypertension (HTN or HT), also known as high blood pressure or arterial hypertension, is a chronic medical condition in which the blood pressure in the arteries is elevated. Blood pressure is expressed by two measurements, systolic and diastolic, which depend on whether the heart muscle is contracting (systole), or relaxed between contractions (diastole). This equals the maximum and minimum pressure, respectively. Normal blood pressure at rest is 100–140 millimeters mercury (mmHg) systolic (top reading) and 60–90 mmHg diastolic (bottom reading). Hypertension is said to be present if it is persistently at or above 140/90 mmHg.
Hypertension usually does not cause symptoms, but it is a major risk factor for hypertensive heart disease, coronary artery disease, stroke, aneurysms of the arteries (e.g.aortic aneurysm), peripheral artery disease and chronic kidney disease.
Hypertension is classified by cause as either primary (essential) hypertension or secondary hypertension; about 90–95% of cases are categorized as primary hypertension which means high blood pressure with no obvious underlying medical cause. The remaining 5–10% of cases categorized as secondary hypertension is caused by identifiable conditions such as kidney disease, narrowing of the aorta or kidney arteries, or endocrine disorders such as excess aldosterone or excess cortisol.
Dietary and lifestyle changes can improve blood pressure control and decrease the risk of health complications, although treatment with medication is still often necessary in people for whom lifestyle changes are not enough or not effective. The treatment of moderately high arterial blood pressure (defined as >160/100 mmHg) with medications is associated with an improved life expectancy. The benefits of treatment of blood pressure that is between 140/90 mmHg and 160/100 mmHg are less clear, with some reviews finding no benefit[3][4] and other reviews finding benefit.