Hypertension - Causes, Risk Factors, and Treatment
Hypertension is one of the most common health issues along with obesity and diabetes faced by people all over the world. it is often defined as having high blood pressure above 120mmHg/80mmHg for a prolonged period. Having such high blood pressure for extended periods can inflict serious damage on the blood vessels, and predisposes a person to other serious conditions such as stroke.
According to the Center for Disease Control (CDC), about half of the adult population in the United States suffers from hypertension [1]. The occurrence of this disorder in such high numbers has taken people to ignore this condition. This ignorance is even more serious than the disorder itself, as unattended hypertension can lead to serious conditions that can be potentially fatal.
How is Hypertension Caused?
The exact underlying mechanisms which lead to abnormally high blood pressures in individuals are not known, however, the pathologies behind certain risk factors are studied in detail through clinical research. Normal blood pressure regulation in the body is maintained through complex neuro-hormonal coordination in the body.
Kidneys and Renin-Angiotensin System:
The primary system regulating blood pressure is the cardiovascular system, with the heart and arteries playing the primary role. Your kidneys also play a very significant role in regulating the blood pressure in the body through the renin-angiotensin system [2]. The blood volume inside the blood vessels directly determines the amount of force being exerted on the blood vessel walls, which determines the blood pressure of an individual. The kidneys serve to regulate the blood volume by adjusting the amount of water being excreted out of the body through urine. The renin-angiotensin system affects the amount of water being excreted through the kidneys by influencing the distal parts of the kidney.
The Role of Brain:
The brain also plays an important role in regulating the blood pressure of the body through a specific group of neurons situated in the cardiovascular center in the hindbrain. This control is purely automatic and is maintained through sensing any changes in the blood pressure, volume, and blood pH and responding through nervous signals that affect different mechanisms in the body [3].
Blood Vessels:
Another major component regulating blood pressure is the blood vessels themselves. The blood vessels have three layers, out of which the innermost layer is known as the endothelium. The endothelium is made up of endothelial cells which secrete some factors such as nitric oxide (NO). Nitric oxide is the most important factor that determines the tone of smooth muscles in the blood vessels, thereby causing vasodilation (increase in the lumen size of blood vessels) according to the needs of the body. Vasodilation due to the release of NO causes a decrease in blood pressure. Anything that affects the synthesis and release of nitric oxide in the blood vessels (for example oxidative stress) can lead to resultant vasoconstriction, thereby causing an increase in the blood pressure inside the vessels [4].
Heart:
The heart influences blood pressure through heart rate. An increase in the heart rate due to any cause leads to an increase in the hydrostatic pressure against the blood vessel walls. This increase puts more force on the walls, leading to increased blood pressure. Abnormally increased heart rates for extended periods can lead to hypertension if the blood vessel walls do not function properly to adjust for the increased output.
Risk Factors:
Several risk factors increase the chances of becoming hypertensive. Some of them are listed below:
Genetics:
One of the most important risk factors associated with hypertension is the genetic makeup of the individual. People having a family history of being hypertensive have many chances of becoming hypertensive themselves. Abnormal changes in the genes coding for some specific factors that regulate blood pressure are considered to be the culprit behind people having a genetic predisposition to becoming hypertensive [5].
Age:
The blood vessels of an individual lose their elasticity due to age-related changes. As a result, they become hardened and are unable to adjust to the changing blood volume in the body. The deposition of cholesterol plaques (atherosclerosis) due to decreased physical activity in advanced age and other cardiovascular changes contribute to increased blood pressure in older individuals.
Smoking:
Tobacco smoke causes hypertension by making the blood vessels narrower (vasoconstriction). Nicotine in tobacco smoke is associated with increased heart rate and blood pressure through various mechanisms.
Obesity:
Obesity is defined as an abnormally increased amount of fat in the body, with an increased number of adipocytes. The levels of adipocyte-derived angiotensinogen increase in obese people (due to the increased number of adipocytes) as compared to individuals having normal body weight. The increased angiotensinogen increases the blood pressure through vasoconstriction brought about by angiotensin II [6].
Excessively Salty Diet:
Salt contains sodium, and using salt in excess leads to increased amounts of sodium in the body. as a result, the body starts retaining water which leads to an increase in blood volume. Increased blood volume is responsible for elevated blood pressure in people who use excess salt in their diet.
Management and Treatment:
Non-pharmacologic Management:
The management of hypertension to avoid the progression from a prehypertensive to a proper hypertensive stage is done through lifestyle changes. Lifestyle changes include limiting the amount of salt in the diet and adequate exercise to prevent the formation of atherosclerotic plaques due to high cholesterol. Moreover, people having a genetic predisposition to hypertension need to abide by the preventive lifestyle more strictly as they have a family history of hypertension.
Smoking cessation also has a lot of importance for the people trying to control their elevated blood pressures. Nicotine and tobacco smoke can lead to high blood pressure through various mechanisms, and stopping smoking is an important lifestyle modification for people with hypertension.
Using less amount of salt in the diet directly affects the blood pressure in hypertensive persons. Salt can also be modified chemically to contain less amount of sodium, which is beneficial for people with elevated blood pressures.
Weight reduction and getting rid of excess cholesterol in the body through sufficient aerobic exercise are essential in controlling hypertension through non-pharmacological interventions. The consumption of fruits rich in potassium, magnesium, and calcium is also found to be beneficial for controlling high blood pressure.
Stress and anxiety appear to be a direct trigger for high blood pressure. Maintaining a balanced lifestyle free of any stress can help control blood pressures in hypertensive people.
Pharmacologic Interventions:
Pharmacologic treatment includes long-term administration of diuretics and angiotensin-converting enzyme inhibitors such as lisinopril and receptor blockers such as losartan. Other pharmacologic agents used for severe hypertension include calcium channel blockers such as verapamil and beta-blockers such as metoprolol.
References:
- Facts About Hypertension | cdc.gov. Centers for Disease Control and Prevention. (2021). Retrieved 29 July 2021.
- Oparil, S., Acelajado, M., Bakris, G., Berlowitz, D., Cífková, R., & Dominiczak, A. et al. (2018). Hypertension. Nature Reviews Disease Primers, 4(1).
- Control of Blood Pressure | Boundless Anatomy and Physiology. Courses.lumenlearning.com. (2021). Retrieved 29 July 2021.
- Spieker, L., Flammer, A., & Lüscher, T. The Vascular Endothelium in Hypertension. The Vascular Endothelium II, 249-283.
- Potter, L., Yoder, A., Flora, D., Antos, L., & Dickey, D. (2009). Natriuretic Peptides: Their Structures, Receptors, Physiologic Functions, and Therapeutic Applications. Cgmp: Generators, Effectors And Therapeutic Implications, 341-366.
- Yiannikouris, F., Karounos, M., Charnigo, R., English, V., Rateri, D., Daugherty, A., & Cassis, L. (2012). Adipocyte-specific deficiency of angiotensinogen decreases plasma angiotensinogen concentration and systolic blood pressure in mice. American Journal Of Physiology-Regulatory, Integrative And Comparative Physiology, 302(2), R244-R251.
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