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Hypertension

What is hypertension?1,2

Systemic arterial hypertension is characterized by persistently high blood pressure (BP) in the systemic arteries. BP is commonly expressed as the ratio of the systolic BP and the diastolic BP. The BP thresholds that define hypertension depend on the measurement method1,2 (Table 1). A positive family history is a frequent occurrence in patients with hypertension, with the heritability estimated to be between 35% and 50% in the majority of studies. Hypertension is the most common preventable risk factor for cardiovascular disease (CVD), chronic kidney disease and cognitive impairment and is the leading single contributor to all-cause mortality and disability worldwide1.

Table 1. Definitions of hypertension based on the 2018 ESH/ESC guidelines2

Category Systolice BP (mmHg)   Diastolic BP (mmHg)
Office BP* ≥140 and/or ≥90
Ambulatory BP      
Daytime (or awake) mean ≥135 and/or ≥85
Nighttime (or asleep) mean ≥120 and/or ≥70
24-h mean ≥130 and/or ≥80
Home BP mean ≥135 and/or ≥85

The pathophysiology of hypertension1,3

Hypertension can be classified as primary or secondary, with most patients having primary hypertension. The cause of hypertension is multifactorial in nature, with environment, genetics, and social determinants having the potential to contribute to its development3.

  • Blood pressure regulation1
    Malfunction or disruption of factors involved in BP control in any component of this integrated neurohumoral system can directly or indirectly lead to increases in mean BP, BP variability or both, over time resulting in target-organ damage and CVD outcomes. The probability of developing hypertension increases with ageing, owing to progressive stiffening of the arterial vasculature caused by, among other factors, slowly developing changes in vascular collagen and increases in atherosclerosis.
  • Sodium homeostasis regulation1
    Sodium is a crucial regulator of blood volume: high serum sodium concentration promotes fluid (water) retention, thereby increasing blood volume and BP. When dietary sodium increases in normotensive individuals, compensatory hemodynamic changes occur to maintain constant BP. These changes include reduction in renal and peripheral vascular resistance and increased production of nitric oxide (NO, a vasodilator) from the endothelium. However, if the effect of NO is impaired or absent, an increase in BP occurs. Endothelial dysfunction is a risk factor for the development of salt sensitivity and subsequent hypertension.
  • Renin–angiotensin–aldosterone system (RAAS)1
    The RAAS has wide-ranging effects on BP regulation, mediating sodium retention, pressure natriuresis (that is, the mechanism whereby increases in renal perfusion pressure (the gradient between renal arterial and venous BP) lead to decreased sodium reabsorption and increased sodium excretion), salt sensitivity, vasoconstriction, endothelial dysfunction and vascular injury and plays an important part in the pathogenesis of hypertension.
Overview_Figure_1_renew

Figure 1. The major neuroendocrine systems involved in the regulation of blood pressure1. Neurohumoral, immune and organ systems involved in the maintenance of BP.

Facts about hypertension4

The prevalence of hypertension in Taiwan is 24.1% and only 57.2% of patients have been treated4

  • Data from the Directorate-General of Budget Accounting and Statistics of Taiwan in 2018 reported a hypertension prevalence rate of 24.1% with an awareness rate of 72.8% and a treatment rate of 57.2%.
  • According to the official statistics of the Taiwan Ministry of Health and Welfare, the age-standardized death rate from CVD, including hypertension, decreased by 54.3% between 1991 and 2015, from 195.2 to 89.2 deaths per 100,000 persons, and was lower than similar rates across the East Asia.

Symptoms5

Most people with high BP have no signs or symptoms, even if blood pressure readings reach dangerously high levels.

A few people with high BP may have headaches, shortness of breath or nosebleeds, but these signs and symptoms aren't specific and usually don't occur until high BP has reached a severe or life-threatening stage.

Causes3,5

Primary hypertension

For most adults, there's no identifiable cause of high BP. This type of high BP, called primary hypertension, tends to develop gradually over many years5.

Secondary hypertension

Secondary hypertension should be considered in young patients without a family history of arterial hypertension, in patients with resistant hypertension, and in patients with a late sudden onset of hypertension. In addition to medical history, a secondary cause might be suggested by symptoms, examination findings, or laboratory abnormalities (Table 2)3.

Table 2. Signs and symptoms suggesting specific causes of secondary hypertension

  Possible diagnosis Diagnostic tests
Different blood pressure (≥20/10 mm Hg) between upper and lower extremities, right and left arms, or both; delayed femoral pulsations, interscapular ejection murmur, rib notching on chest radiograph Coarctation of the aorta Echocardiography, chest radiograph, MRI
Peripheral oedema, pallor, loss of muscle mass Renal parenchymal disease Creatinine, ultrasound of the kidney
Abdominal bruits, peripheral vascular disease Renal artery stenosis Duplex, CT, MRI, angiography
Fatigue, constipation, polyuria, polydipsia, muscle weakness Primary aldosteronism Aldosterone–renin ratio
Weight gain, impotence, fatigue, psychological changes, polydipsia and polyuria, obesity, hirsutism, skin atrophy, striae rubrene, muscle weakness, osteopenia Cushing’s syndrome 24 h urinary cortisol, dexamethasone testing
Headache, palpitations, flushing, anxiety, paroxysmal hypertension, pounding, headache, perspiration, palpitations, pallor Pheochromocytoma Plasma or 24 h urinary metanephrines, 24 h urinary catecholamine
Palpitations, weight loss, anxiety, heat intolerance, tachycardia, atrial fibrillation, accentuated heart sounds, exophthalmos Hyperthyroidism (thyroid disease) Thyroid stimulating hormone, tri-iodothyronine, thyroxine
Weight gain, fatigue, obstipation, bradycardia, muscle weakness, myxedema Hypothyroidism (thyroid disease) Thyroid stimulating hormone, tri-iodothyronine, thyroxine
Snoring, daytime sleepiness, morning headache, irritability, increase in neck circumference, obesity, peripheral oedema Obstructive sleep apnea Screening questionnaire, polysomnography

Although the definition of arterial hypertension differs between guidelines, the indications for antihypertensive therapy are similar: patients with a blood pressure of at least 140/90 mmHg should be treated if the cardiovascular risk is high or if signs of target organ damage are present. All guidelines agree that assessment of hypertension-mediated organ damage is needed to estimate the cardiovascular risk of a patient with hypertension3.

Risk factors5

  • Age: The risk of high BP increases as age. Until about age 64, high BP is more common in men. Women are more likely to develop high BP after age 65.
  • Race: High BP is particularly common among people of African heritage, often developing at an earlier age than it does in whites. Serious complications, such as stroke, heart attack and kidney failure, also are more common in people of African heritage.
  • Family history: High BP tends to run in families.
  • Being overweight or obese: The more you weigh, the more blood you need to supply oxygen and nutrients to your tissues. As the amount of blood flow through your blood vessels increases, so does the pressure on your artery walls.
  • Not being physically active: People who are inactive tend to have higher heart rates. The higher your heart rate, the harder your heart must work with each contraction and the stronger the force on your arteries. Lack of physical activity also increases the risk of being overweight.
  • Using tobacco: Not only does smoking or chewing tobacco immediately raise BP temporarily, but the chemicals in tobacco can damage the lining of artery walls. This can cause the arteries to narrow and increase the risk of heart disease. Secondhand smoke also can increase heart disease risk.
  • Too much sodium in diet: Too much sodium in diet can cause the body to retain fluid, which increases BP.
  • Too little potassium in diet: Potassium helps balance the amount of sodium in cells. A proper balance of potassium is critical for good heart health.
  • Drinking too much alcohol: Over time, heavy drinking can damage the heart. Having more than one drink a day for women and more than two drinks a day for men may affect BP.
  • Stress: High levels of stress can lead to a temporary increase in BP. Stress-related habits such as eating more, using tobacco or drinking alcohol can lead to further increases in BP.
  • Certain chronic conditions: Certain chronic conditions also may increase the risk of high BP, including kidney disease, diabetes and sleep apnea.

Incidence and prevalence6

The global mean age-standardized systolic BP was 127.0 mmHg in men and 122.3 mmHg in women, whereas the mean age-standardized diastolic BP was 78.7 mmHg in men and 76.7 mmHg in women. Higher mean systolic and diastolic BPs in both men and women were found in South Asia, sub-Saharan Africa, and Central and Eastern Europe, whereas lower mean BPs were found in high-income Western and high-income Asia-Pacific regions.

The age-standardized prevalence of hypertension was slightly higher in men (31.9%) than in women (30.1%) and was lower in high-income countries (28.5%) than in low and middle-income countries (31.5%).

Footnotes:

  • *  Refers to conventional office BP rather than unattended office BP.
  • BP, blood pressure; CVD, cardiovascular disease; ESC, European Society of Cardiology; ESH, European Society of Hypertension; NO, nitric oxide; RAAS, Renin–angiotensin–
    aldosterone system; SNS, sympathetic nervous system; Treg, regulatory  T.

References:

  1. Oparil S, et al. Nat Rev Dis Primers. 2018;4:18014.

  2. Williams B, et al. European Heart Journal (2018) 39, 3021–3104.

  3. Brouwers S, et al. Lancet. 2021;398(10296):249-261.

  4. Cheng HM, et al. J Clin Hypertens (Greenwich). 2020;22(3):511-514.

  5. High blood pressure (Hypertension) Symptoms and cause. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/symptoms-causes/syc-20373410 
    Accessed 28 Aug 2021.

  6. Mills KT, Stefanescu A, He J. Nat Rev Nephrol. 2020;16(4):223-237.

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