What is Hypertension?
According to the World Health Organization (WHO), hypertension is a medical condition in which a person has abnormally high blood pressure that is persistent and above the treatment required. It is commonly known as high blood pressure. Blood pressure is the amount of force created by the force of blood pushing against the walls of blood vessels (arteries) as it is pumped by the heart. Hypertension is one of the most common non-communicable diseases affecting the world population at large, and a large majority of Nigerians in particular.
The blood pressure is measured by two values namely systolic and diastolic blood pressure. Systolic blood pressure is the force the blood exerts on the artery wall when the heart is actively beating, i.e., pumping blood. It is usually recorded as the first value. The diastolic blood pressure is the force the blood exerts on the artery wall when the heart is at rest i.e., in between beats. It is recorded as the second value.
In general, a blood pressure reading greater than 140/90mmhg is considered an elevated value and requires some form of clinical intervention.
How Common is Hypertension and Who Has It?
Hypertension is one of the most common non-communicable diseases in the world today and affects virtually every 1 in 3 adults including pregnant women. Although recent studies have shown that individuals below the age of 40 years are beginning to develop high blood pressure, and this could be due to several factors including ethnic and social factors.
Classification of Hypertension in Adults
Hypertension in adults can be classified as:
- Normal blood pressure (120/80) – systolic 120-129 and diastolic 80-89.
- High normal (130/85) – systolic 130-139 and diastolic 85-89.
- Stage 1 (Mild hypertension - 140/90) – systolic 140-159 and diastolic 90-99.
- Stage 2 (Moderate hypertension - 160/100) – systolic 160-179 and diastolic 100-109.
- Stage 3 (Severe hypertension - 180/110) – systolic greater than 180 and diastolic greater than 110.
- Hypertensive urgency (No organ damage – 180/30) – usually greater than 180 systolic and greater than 130 diastolic.
- Hypertensive emergency (Rapid increase in blood pressure is evidence of acute organ damage).
What Causes Hypertension?
The exact cause of hypertension can be attributed to a definite cause such as kidney diseases endocrine diseases etc. or an unknown cause, the latter being referred to as idiopathic hypertension. Idiopathic hypertension has many risk factors. Some of these factors are hereditary while some are reversible i.e., social/behavioural factors can be avoided if proper preventive health measures are taken.
Types of Hypertensions
Hypertension may be classified as:
- Essential or Primary Hypertension (Idiopathic hypertension)
- Secondary Hypertension (due to specific diseases or organ damage)
- Pregnancy-Related Hypertension (pre-eclampsia)
- White Coat Hypertension (anxiety induced in the clinic by uniformed health workers)
- Isolated Systolic Hypertension (ISH)
Essential or Primary Hypertension
Essential hypertension or primary hypertension occurs when the cause of the hypertension isn’t linked to any other disease process in the body. It occurs mostly in hypertensive patients, and there is no obvious cause. Instead, it could develop due to environmental as well as genetic factors.
Some of these genetic and environmental factors are reversible and irreversible and include:
Irreversible Risk Factors
- Age: Increased age predisposes to a higher likelihood of hypertension.
- Gender: Hypertension is more common in men than women, especially during childbearing age. Women are more likely to develop high blood pressure after menopause.
- Family History: Considering a genetic standpoint, people with a family history of hypertension have a proven risk of having hypertension.
- Africans and African-Americans (Black Race): These subtypes of people have been shown to have an increased tendency to develop hypertension, although other secondary factors are at play. Hypertension is a Blackman’s disease.
Reversible Risk Factors
- Obesity: This is an excessive and abnormal fat accumulation that harms health. The more one weighs the more the need for blood to supply oxygen and nutrient to tissues. As the volume of blood circulating through the blood vessels increases so does the pressure on artery walls. Obesity has been identified as a risk factor for hypertension. People may have obese abdomens from excessive drinking of sugary drinks, alcohol, and traditional large carbohydrate meals. Weight reduction has been noted to reduce the severity of hypertension.
- Physical Activity: Lack of physical activity is a risk factor for hypertension. Inactive people have a higher heart rate. Lack of physical activity also increases the risk of being obese.
- Tobacco Smoking: Not only does smoking tobacco immediately raise blood pressure temporarily, but the chemicals in tobacco can damage the lining of the artery walls. This can cause arteries to narrow, increasing blood pressure.
- Diet: Certain diets can be an implicating factor towards hypertension, and they could include -
- Excessive Salt Intake: Eating too much salt (sodium) in the diet causes the body to retain fluid which increases blood pressure.
- Potassium helps to balance the amount of sodium in cells. A low potassium diet increases the risk while diets high in potassium (e.g., fruits such as bananas, etc.) lower the risk of hypertension.
- Excessive Caffeine Intake: Having too much or excessive intake of caffeine especially among coffee takers has been implicated to be a likely risk factor for hypertension. (See below)
- Heavy alcohol use can damage the heart. Having more than 3 drinks at a time temporarily raises blood pressure as it may cause the body to release hormones that increase the blood flow and heart rate. Drinking too much alcohol can raise blood pressure to unhealthy levels. Repeated binge drinking can lead to long-term increases in blood pressure.
- Vitamin D: Too little vitamin in the diet may lead to high blood pressure. Researchers think Vitamin D may affect an enzyme the kidney produces that affects blood pressure. (See below)
- Fat (Cholesterol) in Diet: Fats block the inside of the blood vessels and cause an increase in blood pressure. It is also associated with increased body weight (obesity). (See below)
Caffeine and Blood Pressure
Caffeine may cause a short-term dramatic increase in your blood pressure even if you do not have high blood pressure. It is unclear what causes the spike in blood pressure. The blood pressure response to caffeine differs from person to person. Some researchers believe that caffeine could block a hormone that helps to keep your arteries widened. Others think that caffeine causes your adrenal glands to release more adrenaline which causes your blood pressure to increase. Some people who regularly drink caffeinated beverages have a high average blood pressure than those who drink none. Others who regularly drink caffeinated beverages develop a tolerance to caffeine. As a result, caffeine does not have a long-term effect on their blood pressure.
Effects of Vitamin D on Blood Pressure
Effects of vitamin D on hypertension risk and blood pressure have been explored widely in cohort studies and randomized control trials but whether the association is causal is still unknown. Vitamin D supplement is ineffective to prevent hypertension i.e., vitamin D does not lower blood pressure in the general population.
Effects of Cholesterol on Blood Pressure
Cholesterol plaque and calcium cause your arteries to become hard and narrow. So, your heart has to strain much harder to pump blood through them. As a result, your blood pressure becomes too high. When the body cannot clear cholesterol from the bloodstream, that excess cholesterol can deposit along artery walls. When arteries become stiff and narrow for deposits, the heart has to work overtime to pump blood through them. This causes blood pressure to go up.
This can be described as hypertension due to a known, proven cause in the body. There are many such causes which can be categorized as:
- Kidney Diseases: Renal malfunction is one of the most common causes of secondary hypertension. Some of the renal conditions implicated are Chronic Kidney Disease, Urinary Tract Obstruction, Renal vasculitis, Coarctation of the aorta, and Polycystic Kidney disease amongst others.
- Diabetes Mellitus (DM): People who are diagnosed with DM may also have a higher tendency to develop hypertension.
- Endocrinal Causes: Hormone imbalances have also been shown to cause secondary hypertension. Some of these conditions include Cushing syndrome, primary aldosteronism, and others.
- Use of Oral Contraceptives: Studies have shown that women who use oral contraceptives are more likely to develop secondary hypertension. This likelihood is increased if she is above the age of 35 years, is obese, and has a family history of hypertension.
- Use of Drugs and Other Substances: Some drugs that have been implicated include corticosteroids, erythropoietin, decongestants that contain ephedrine, adrenergic drugs, and others. Substances include cocaine, nicotine, and alcohol amongst others.
- Neurogenic Causes: These factors originate primarily from the brain and they include certain types of brain tumors, autonomic dysfunction, intracranial hypertension, sleep apnea, and others.
Pregnancy-Related Hypertension (Pre-Eclampsia)
This is hypertension that occurs only during pregnancy. It is to be noted that there is usually a drop in blood pressure in normal pregnancy and levels considered normal in a non-pregnant person may be hypertension in pregnancy e.g., 140/90.