Hypertension: Prevalence, Distribution and Hypotheses

1. Definition and Symptoms
Hypertension is the result of persistent high arterial blood pressure, which may cause damage to the vessels and arteries of the brain, eyes, heart, and kidneys. The entire circulatory system is affected as it becomes increasingly difficult for blood to travel from the heart to the major organs. Multiple blood pressure readings are taken to establish an average, then analyzed by a physician to determine hypertension, defined as blood pressure excess of 140/90 mm Hg. Hypertension is known as “the silent killer” for its generally asymptomatic with no noticeable signs or symptoms and often discovered through regular check-ups with a healthcare provider. A few people have reported headaches, blurring of vision, chest pain, and frequent urination at night, although these signs and symptoms aren’t specific, and don’t occur until high blood pressure has reached a severe or life-threatening stage. Uncontrolled high blood pressure significantly increases the risk of developing dangerous health complications, like heart attack and stroke.

2. Prevalence, Incidence and Mortality

2.1 Prevalence
Hypertension is an important global health problem due to its high prevalence and resultant cardiovascular and chronic kidney diseases. The occurrence of hypertension is rising globally, with projections evaluating up to a 30% increase in prevalence by the year 2025. The prevalence of hypertension varies considerably by region, which can be attributable to several aspects like growing trends in sedentary lifestyle, obesity, nutritional transition, and other modifiable risk factors, such as insufficient healthcare systems. Subsequently, populations of low- and middle-income carry a higher burden of hypertension compared to the global average of one-third of the adult population in these countries. In terms of the overall burden of hypertension, trends in prevalence signify disparities in awareness, treatment, and control rates of hypertension disease between low/middle-income and high-income countries.                                                                                                      
2.2 Incidence

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Formerly a major public health issue in developed countries, hypertension is no longer a dominant problem of the Western world or wealthy countries. This may be a result from better diets enriched with more fruit and vegetables, as well as better access to healthcare, whereby elevated blood pressure can be detected early by a healthcare provider and treated properly with medications and long-term treatment. However, hypertension remains a problem of the world’s poorest countries and people, particularly of low- and middle- income. Hence, effective blood pressure management has been shown to decrease the incidence of cardiovascular disease, including heart attack, heart failure and stroke.
2.3 Mortality
Hypertension drives the global burden of cardiovascular disease and is the leading preventable risk factor for premature death and/or disability. Mortality from hypertensive disease is largely due to atherosclerotic cardiovascular sequela including coronary disease, ischemic heart disease, and cardiac failure. Several studies of hypertension control have been conducted in various epidemiological and practice settings. Researchers have shown hypertension to be highly prevalent, relatively poorly treated, and a crucial health crisis due to its increasing morbidity, mortality and financial costs to society. Randomized controlled trials have convincingly proven treatment of hypertension reduces the risk of coronary heart disease, congestive heart failure, stroke and mortality. Without effective intervention, the burden of hypertension will only magnify the epidemic of cardiovascular and kidney diseases, particularly in populations of low-and middle-income countries.
 

3. Distribution of Hypertension by Person, Place, and Time factors

3.1 Person Factor – Gender, Age, Race/Ethnicity, and SES

A progressive rise in blood pressure with increasing age is observed nationwide. Studies demonstrate that men are more inclined to hypertension than women below the age of 50, however, in advanced-age, women are at a higher risk for developing hypertension disease due to menopause when estrogen levels fall. Black individuals have a higher prevalence and incidence of hypertension than Caucasian individuals. For persons under 65 years of age, stroke mortality rate is three times greater in Blacks than whites, widely attributed to a higher prevalence and increased severity of hypertension in Blacks. Mexican Americans and Native Americans have lower blood pressure control rates compared to non-Hispanic white persons and black individuals. Across the income groups of countries, hypertension is consistently higher in populations in low, lower-middle and upper-middle countries compared to global average.
3.2 Place Factor

Place factors emphasize the environmental variables that may aid in onset or development of a disease, such as where an individual was born, lives or works. Researchers use differences in place variables to make comparisons on a national, international, and urban vs. rural level. Based on global health observatory data across the World Health Organization (WHO) regions, hypertension was reported highest in Africa in both sexes with prevalence rates over 40%. The lowest prevalence of hypertension was observed in the Americas in which men had higher prevalence estimates compared to the women. Among the income groups of countries, the prevalence of raised blood pressure was consistently high, with low/lower-middle and upper-middle income countries compared to high-income countries. Results can be explained through disparities in awareness, prevention, treatment and control between populations.
(Refer to Figure 1).

Figure 1: Bar graph depicting percent of population with elevated blood pression based on WHO region, gender and socioeconomic status.                                                                                  

3.3 Time Factor – Secular Trend

Secular trends in hypertension and cardiovascular sequelae are of great public health importance because of the insights gained of determinants and continuing contribution to national morbidity and mortality of hypertension disease. For example, the Framingham Heart Study, begun in 1948, initially explored the epidemiologic relationship of blood pressure to coronary vascular disease in men and women and how this risk is further affected by age. Framingham researchers later provided evidence that diastolic blood pressure (DBP) <70 mm Hg with systolic blood pressure (SBP) ≥120 mm Hg was related with a CVD risk equivalent to about 20 mm Hg of additional elevation in SBP, supporting the significance of elevated blood pressure as a coronary vascular disease risk factor (Refer to Figure 2). Data from the Framingham Heart Study also indicated that cardiovascular disease risk increased 2.5-fold in women and 1.6-fold in men with high-normal blood pressures (systolic blood pressure 130–139 mm Hg or diastolic blood pressure 85–89 mm Hg). As such, careful monitoring of the Framingham Study population has led to the identification of major CVD risk factors, as well as valuable information on the effects of these factors such as blood pressure, age, gender, and other variables that are used in research today.

Figure 2: Observed, predicted, and best fit mean hypertension risks of predicted risk obtained from the Framingham hypertension model.

4. Summary of Potential Hypotheses

4.1 Hypothesis for “Person” Factor

It has been hypothesized that a temporal relationship exists between age, obesity, race/ethnicity, and socioeconomic status with hypertension disease. Researchers suggest that advanced-age and increased body weight are reliable indicators of hypertension, given that prevalence estimates of hypertension are substantially higher in the elderly, in contrast to younger adults, and in overweight/obese individuals, compared to normal weight individuals. Increasing evidence also proposes poor nutrition in early life increases the risk of hypertension in later life, which may clarify the developing problem in poor countries.
4.2 Hypothesis for “Place” Factor
Researchers hypothesize that there is a greater prevalence of hypertension in lower-income and rural areas, although significantly less treated. Within the United States alone, southern residents of all ethnicities and genders have been shown to have a hypertension prevalence higher than that in other regions of the US. With this in mind, risk factors of hypertension in today’s times are no longer related to affluence but is now a major health issue correlated with poverty.
4.3 Hypothesis for “Time” Factor

Researchers hypothesize that the prevalence, incidence, and mortality rates of hypertensive can be described by a secular trend of hypertensive disease control. An overall decline in mortality has been indicated. Through examination of hypertension prevalence, awareness, treatment, and control globally, researchers have noted global hypertension disparities are large and increasing in low- and middle-income countries. With this in mind, analysts have rationalized that declines in mortality are related to better awareness, regular checkups with a health care provider, and effective anti-hypertensive therapy.
 

5. Suggested Areas for Further Epidemiological Research

Despite a greater understanding of the risks of elevated blood pressure and the increasing availability of effective antihypertensive therapy, hypertension continues to affect a large proportion of the world’s population. To further understand the epidemiology of hypertension, there is a need for studies to accurately predict future trends of hypertension prevalence estimates of global burden. Hypertension in high-income and low- and middle-income countries are vital in bettering us comprehend the rising public health concern of hypertension. 

References

1. Definition

• High blood pressure (hypertension). (2018, May 12). Retrieved from https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/symptoms-causes/syc-20373410

2. Prevalence

• Sarki, A. M., Nduka, C. U., Stranges, S., Kandala, N., & Uthman, O. A. (2015, December). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5058882/
• Bloch, M. J. (2016). Worldwide prevalence of hypertension exceeds 1.3 billion. Journal of the American Society of Hypertension,10(10), 753-754. Retrieved from https://www.ashjournal.com/article/S1933-1711(16)30489-2/pdf

2. Incidence

• 1 billion people worldwide have high blood pressure. (2017, May 2). Retrieved from http://www.bloodpressureuk.org/mediacentre/Newsreleases/1billionpeopleworldwidenowhavehighbloodpressure

2. Mortality

• Raised blood pressure. (2015, February 01). Retrieved from http://www.who.int/gho/ncd/risk_factors/blood_pressure_prevalence_text/en/
• Hypertension Epidemiology |. (n.d.). Retrieved from https://www.omicsonline.org/conferences-list/hypertension-epidemiology

3. Factors

• Person factor
  • Epidemiology of Hypertension. (2018, April 22). Retrieved from https://emedicine.medscape.com/article/1928048-overview#showall
  • Hypertension differs in Males and Females. (2018, January 19). Retrieved from https://ihealthlabs.com/find-hypertension-differs-males-females/                              
• Place factor
  • Raised blood pressure. (2015, February 01). Retrieved from http://www.who.int/gho/ncd/risk_factors/blood_pressure_prevalence_text/en/
• Figure 1
  • Raised blood pressure. (2015, February 01). Retrieved from http://www.who.int/gho/ncd/risk_factors/blood_pressure_prevalence_text/en/
• Time factor
  • Kannel, W. B., & Wolf, P. A. Inferences from secular trend analysis of hypertension control. American Journal of Public Health,82(12), 1593-1595. Retrieved from https://ajph.aphapublications.org/doi/pdf/10.2105/AJPH.82.12.1593
  • Franklin, S. S., & Wong, N. D. (2013, March). Hypertension and cardiovascular disease: Contributions of the framingham heart study. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/25690263
  • Framingham heart study. Retrieved from https://www.framinghamheartstudy.org/fhs-about/
     
• Figure 2
  • Carson, A. P., Lewis, C. E., Jacobs, D. R., Peralta, C. A., Steffen, L. M., Bower, J. K., . . . Muntner, P. (2013, December). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4019674/                                                                                                                          

4. Hypothesis

• “Person” Factor
  • Hajjar. I, Morley J., Kotchen A. T. Hypertension: trends in prevalence, incidence, and control. Retrieved from https://www.annualreviews.org/doi/pdf/10.1146/annurev.publhealth.27.021405.102132
• “Place” Factor
  • Sarki, A. M., Nduka, C. U., Stranges, S., Kandala, N., & Uthman, O. A. (2015). Prevalence of Hypertension in Low- and Middle-Income Countries. Medicine,94(50). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5058882/

• “Time” Factor
  • Bloch, M. J. (2016). Worldwide prevalence of hypertension exceeds 1.3 billion. Journal of the American Society of Hypertension,10(10), 753-754. Retrieved from: https://www.ashjournal.com/article/S1933-1711(16)30489-2/pdf
  • Hajjar. I, Morley J., Kotchen A. T. Hypertension: trends in prevalence, incidence, and control. Retrieved from https://www.annualreviews.org/doi/pdf/10.1146/annurev.publhealth.27.021405.102132

5. Further Research

• Sarki, A. M., Nduka, C. U., Stranges, S., Kandala, N., & Uthman, O. A. (2015, December). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5058882/
• Mills, K. T., Bundy, J. D., Kelly, T. N., Reed, J. E., Kearney, P. M., Reynolds, K., . . . He, J. (2016, August 09). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4979614/