The Epidemiology of Hypertension

1

What is the prevalence of hypertension?

Hypertension is a major global public health problem and is estimated to impact nearly a third of the world’s population (1.13 billion people). In the 1970s, higher-income Western countries were known to have the highest prevalence of hypertension when compared to low-income countries, as evidenced by a pooled analysis of 1479 population studies from 200 countries. However, between 1975 and 2015, this trend effectively reversed. Among those who had hypertension, the proportion of people living in low-income countries was 66% in 2000 and more recently has grown to 75%. The average systolic blood pressures (SBPs) have dropped by 2 to 3 mm Hg in Western and high-income Asian-Pacific countries, whereas the highest average SBPs in 2015 were found in Southeast Asia and sub-Saharan Africa.

According to a 2017 report by the National Center for Health Statistics (NCHS), the prevalence of hypertension in American adults from 2015 to 2016 was estimated to be around 29%. Although the percentage of hypertensive adults in the United States has not significantly changed between 1999 and 2016, the proportion of controlled blood pressure (BP) has improved from 32% to 48% during this period.

With the recent changes in hypertension definitions introduced by the American College of Cardiology/American Heart Association (ACC/AHA) 2017, the prevalence of hypertension in the United States expanded from 31% to 45%, thus identifying a growing need for more widespread awareness as well as need for preventive and treatment strategies to reduce the burden of hypertension and downstream health outcomes.

2

Which groups have a higher risk of developing hypertension and its complications?

With each decade of life, hypertension becomes more common. By 75 years of age, more than 70% of Americans meet the criteria for hypertension based on the ACC/AHA definitions. Male gender is associated with higher rates of hypertension before the age of 65 as compared to women (age 20–44 years: 30% vs. 19%; age 45–54 years: 50% vs. 44%; and age 55–64 years: 70% vs. 63%, respectively). However, women older than the age of 75 have a higher prevalence of hypertension (85%) and higher average BPs compared to older men in the same age group (79%). Overall, men are less likely to be aware that they have hypertension and have higher rates of uncontrolled BP.

African Americans (AAs) are known to have higher risk of developing hypertension and related end-organ complications. The National Health and Nutrition Examination Survey (NHANES) of American adults between 2013 and 2016 found that the prevalence of hypertension was highest in Blacks (31%) compared to Whites (22%) and Mexican Americans (22%). This racial disparity persisted in spite of adjustments for demographics, socioeconomic status, and comorbidities. Similarly, in the Multiethnic Study of Atherosclerosis (MESA) study, investigators have shown an increased incidence rate ratio (IRR) for hypertension among Blacks (IRR = 2.1, 95% confidence interval [CI] = 1.5 to 2.9) as compared to Whites.

Mexican Americans have lower rates of awareness of the diagnosis of hypertension (28%) as compared to Whites (35%) and Blacks (43%). A larger proportion of hypertensive Blacks and Mexican Americans in NHANES have uncontrolled BP (37% and 38%, respectively) as compared to Whites (28%). These ethnic disparities in hypertension are important to recognize because of disproportionate clinical outcomes in minority populations. AAs experience greater rates of end-stage kidney disease (ESKD), cardiovascular disease (CVD), and all-cause mortality when compared to Whites. Recent studies in different settings demonstrate the incidence of CVD outcomes in AAs is 50% to 100% higher than in Whites. Similarly, the incidence of ESKD in Hispanics is 50% higher than in Whites, although studies have not consistently found an associated increase in mortality risk or CVD events. These findings are largely due to the fact that epidemiological studies to date have not adequately represented the Hispanic population; data from NHANES has largely been limited to Mexican Americans, and further epidemiological studies are needed to examine the disaggregated profiles of specific ethnicities within this culturally, socioeconomically, and genetically heterogeneous group. For instance, cross-sectional analysis of participants in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL) showed that Dominicans, Cubans, and Puerto Ricans have higher rates of hypertension than those of Mexican background.

3