Hypertension

Hypertension, commonly referred to as high blood pressure, is a chronic medical condition characterised by a persistent elevation of pressure within the arterial system. It generally develops gradually and often remains undetected for long periods because it usually produces no direct symptoms. Despite this lack of obvious signs, hypertension represents a major global health challenge due to its strong association with serious cardiovascular, renal and neurological disorders. It contributes substantially to premature morbidity and mortality worldwide and is recognised as one of the leading modifiable risk factors for disease burden across populations.

Definition and Classification

Blood pressure represents the force exerted by circulating blood against the walls of the arteries and is recorded using two values: systolic pressure, the pressure during cardiac contraction, and diastolic pressure, the pressure during cardiac relaxation. Among healthy adults at rest, typical systolic values range from 100 to 140 mmHg, while normal diastolic values range from 60 to 90 mmHg. Hypertension is diagnosed when readings consistently meet or exceed 130/80 mmHg, with some diagnostic frameworks using 140/90 mmHg as the threshold.
Hypertension is broadly classified into two categories: essential (primary) hypertension and secondary hypertension. Essential hypertension accounts for an estimated 90–95 per cent of all cases, and arises without a single identifiable cause. It is associated with complex interactions among lifestyle factors, environmental influences and genetic predispositions. Secondary hypertension, accounting for the remaining 5–10 per cent of cases, occurs due to underlying, identifiable conditions such as chronic kidney disease, endocrine disorders, renal artery stenosis or specific medications including certain oral contraceptives.

Aetiology and Risk Factors

Essential hypertension develops from non-specific influences that impair vascular regulation. Important contributors include excessive dietary salt intake, obesity, tobacco consumption, physical inactivity and alcohol or drug misuse. Genetic factors also play a significant role, with familial clustering of high blood pressure commonly observed.
Secondary hypertension arises from identifiable pathological mechanisms. For example, endocrine disorders such as Cushing’s syndrome may produce typical signs including abdominal obesity, glucose intolerance and characteristic fat redistribution. Hyperthyroidism may cause weight loss, tremor and tachycardia, while renal artery stenosis can result in abdominal bruits and unequal limb blood pressures. Structural abnormalities such as coarctation of the aorta lead to blood pressure discrepancies between the upper and lower limbs. Tumours such as phaeochromocytomas cause episodic surges of blood pressure accompanied by headache, palpitations and sweating.

Clinical Presentation and Detection

Hypertension is frequently asymptomatic and is often discovered during routine health screening or when investigating unrelated complaints. When symptoms are reported, they may include headaches, light-headedness, tinnitus, visual disturbances or episodes of syncope, although these are generally non-specific and often linked to associated anxiety rather than the pressure elevation itself.
Long-standing, uncontrolled hypertension produces characteristic forms of end-organ damage. Hypertensive retinopathy, visible on ophthalmoscopic examination, reflects chronic vascular injury and correlates with the severity and duration of hypertension. Other key manifestations include chronic kidney disease, left ventricular hypertrophy and vascular damage across major organ systems.

Hypertensive Crisis

Severely raised blood pressure, typically at or above 180 mmHg systolic or 120 mmHg diastolic, constitutes a hypertensive crisis. This is subdivided into hypertensive urgency and hypertensive emergency. In hypertensive urgency, no evidence of acute end-organ damage is present and blood pressure may be lowered gradually over 24–48 hours using oral agents. In hypertensive emergency, there is demonstrable damage to vital organs such as the brain, heart, lungs or kidneys, producing symptoms that may include chest pain, breathlessness, confusion or reduced consciousness. In such cases, blood pressure reduction is required more rapidly to limit ongoing tissue injury, although high-quality trial data guiding the appropriate rate of reduction remain limited.

Hypertension in Pregnancy

Hypertension affects approximately 8–10 per cent of pregnancies and is diagnosed when repeated measurements exceed 140/90 mmHg. It may be categorised as chronic (pre-existing) hypertension, gestational hypertension or pre-eclampsia. Chronic hypertension increases the risk of poor obstetric outcomes such as preterm birth, growth restriction and stillbirth.
Pre-eclampsia, typically arising in the second half of pregnancy or postpartum, features raised blood pressure accompanied by proteinuria. It affects around 5 per cent of pregnancies and accounts for a significant proportion of maternal and perinatal fatalities worldwide. While often asymptomatic, potential manifestations include headaches, visual disturbance, epigastric pain, vomiting and oedema. In severe cases, progression to eclampsia may occur, involving seizures and life-threatening complications such as pulmonary oedema, renal failure and coagulopathies.
Gestational hypertension is defined as new-onset hypertension without proteinuria. Exercise has been shown to reduce the incidence of hypertension-related complications in pregnancy by improving cardiovascular function, enhancing cardiac output and stabilising systolic and diastolic pressures. Aerobic exercise performed five to seven days per week at light to moderate intensity has demonstrated greater blood pressure-lowering effects compared with resistance training, with reductions in systolic blood pressure of 5–15 mmHg being observed.

Diagnosis and Monitoring

Diagnosis typically relies on repeated office-based blood pressure measurements, but 24-hour ambulatory blood pressure monitoring is considered more accurate, as it captures variations across daily activities and sleep. Home blood pressure monitoring is also useful for assessing long-term control and identifying patterns such as white-coat or masked hypertension. Blood pressure thresholds differ for children and adolescents due to age-specific physiological norms.

Management and Treatment

Management focuses on reducing blood pressure to a safe range to prevent or mitigate long-term complications. Lifestyle modification constitutes first-line therapy for most individuals and includes weight loss, regular physical activity, reduction in salt and alcohol intake, smoking cessation and adherence to a balanced diet rich in fruits, vegetables and whole grains.
If lifestyle measures prove inadequate, pharmacological treatment is initiated. Common classes of antihypertensive medications include diuretics, calcium channel blockers, ACE inhibitors, angiotensin receptor blockers and beta-blockers. Up to three medications used in combination can achieve adequate control in about 90 per cent of patients. Evidence strongly supports the treatment of moderate hypertension (≥160/100 mmHg), with clear improvements in life expectancy. For individuals with milder hypertension (130/80–160/100 mmHg), research findings are mixed but many reviews still indicate overall benefit.