Prevalence of Hypertension and Controlled Hypertension — United States, 2007–2010

Cathleen D. Gillespie, MS1

Kimberly A. Hurvitz, MHS2

1National Center for Chronic Disease Prevention and Health Promotion, CDC

2National Center for Health Statistics, CDC

Corresponding author: Cathleen D. Gillespie, MS, Division for Heart Disease and Stroke Prevention, National Center for Health Statistics, CDC. Telephone: 770-488-5855; E-mail: ckg2@cdc.gov.

Introduction

Hypertension is a major risk factor for heart disease and stroke. As the first and fourth leading causes of death in the United States, heart disease and stroke occur in approximately 30% of adults aged ≥18 years in the United States (1). Disparities in the prevalence of hypertension among racial/ethnic groups have persisted at least since 1960, with the prevalence remaining highest among non-Hispanic black adults (1–4). Blood pressure control among those with hypertension can reduce the risk of subsequent cardiovascular diseases (5). Among adults with hypertension, Mexican-American persons born outside the United States, and persons without health insurance had lower rates of blood pressure control in 2005–2008 (3). Not only do non-Hispanic black adults have higher rates of hypertension, but among those with hypertension they also have lower rates of blood pressure control than non-Hispanic white adults (2,3).

Healthy People 2020 includes objectives to reduce the prevalence of hypertension among adults to 26.9% (objective HDS-5.1) and to increase the prevalence of blood pressure control among adults with hypertension to 61.2% (objective HDS-12) (6). Further, in 2011, the U.S. Department of Health and Human Services launched the Million Hearts initiative, which is intended to bring together communities, health systems, nonprofit organizations, federal agencies, and private-sector partners from across the country to prevent 1 million heart attacks and strokes over the course of 5 years (available at http://millionhearts.hhs.gov/index.html). Blood pressure control is a part of the initiative in the prevention of these adverse events. Therefore, hypertension prevalence and blood pressure control among those with hypertension are important indicators to monitor over time to identify improvements or persistent challenges in vulnerable segments of the U.S. population.

This analysis of hypertension and the discussion that follows are part of the second CDC Health Disparities and Inequalities Report (2013 CHDIR) (3).The 2011 CHDIR was the first CDC report to assess disparities across a wide range of diseases, behavioral risk factors, environmental exposures, social determinants, and health-care access. The topic presented in this report is based on criteria that are described in the 2013 CHDIR Introduction (7). This report provides more current information on the prevalence of hypertension and blood pressure control among adults aged ≥18 years. The purposes of this report on hypertension and controlled hypertension are to discuss and raise awareness of differences in the characteristics of persons with hypertension and controlled hypertension, and to prompt actions to reduce disparities.

Methods

To estimate the age-adjusted prevalence of hypertension and blood pressure control among adults aged ≥18 years by selected demographic and health characteristics, CDC analyzed data from the National Health and Nutrition Examination Survey (NHANES) aggregated from two survey cycles: 2007–2008 and 2009–2010. NHANES is a national survey representative of the U.S. civilian noninstitutionalized population. Details of the NHANES survey methodology are available at http://www.cdc.gov/nchs/nhanes/about_nhanes.htm. During 2007–2010, the response rate among persons screened was 76.3%. Data were analyzed for 11,782 participants who had adequate data from the interview and examination components of the survey necessary to determine hypertension status. Blood pressure was determined by an average of up to three measurements taken during a single examination. Hypertension was defined as an average systolic blood pressure (SBP) ≥140 mmHg, an average diastolic blood pressure (DBP) ≥90 mmHg, or if the participant reported the current use of blood pressure lowering medication. Blood pressure control was defined as an average SBP <140 mmHg and an average DBP <90 mmHg among persons with hypertension. Pregnant women were excluded.

Hypertension prevalence and control estimates were analyzed by selected demographic and health characteristics: sex, age group (18–44, 45–64, and ≥65 years), race and ethnicity, marital status, educational attainment, country of birth, family income to federal poverty threshold, health insurance status (for persons aged 18–64 years), veteran status, diagnosed diabetes status, obesity status, and disability. Race was defined as white, black, and Mexican American. Ethnicity was defined as Hispanic or non-Hispanic. Educational attainment among adults aged ≥25 years was defined as follows: less than high school, high school graduate or equivalent, some college or Associate of Arts (AA) degree, and college graduate or above. Household income was defined as family income to federal poverty threshold, as defined by the Department of Health and Human Services poverty guidelines (8), specific to family size and appropriate year and state. Health insurance status was defined as having either private or public insurance, or being uninsured. Obesity among adults aged ≥20 years is defined as a body mass index ≥30 kg/m2 based on measured weight and height. Veteran status, diagnosed diabetes,* and disability† status were self-reported (Table).

Disparities were measured as the deviations from a "referent" category prevalence. The referent group was the group that had the most favorable estimate for the variables used to assess disparities during the period reported. Absolute difference was measured as the simple difference between a population subgroup estimate and the estimate for its respective reference group. The relative difference, a percentage, was calculated by dividing the absolute difference by the value in the referent category and multiplying by 100.

Statistical analyses were weighted to account for the complex survey design. Prevalence estimates, except those by age group, were age adjusted to the 2000 U.S. standard population using the direct method. Estimates of hypertension control that are age-adjusted to the 2000 U.S. standard population tend to be lower than those adjusted to the population with hypertension because of the difference between the age distribution of the general population and that of the population with hypertension (9).

Results

During 2007–2010, the overall age-adjusted prevalence of hypertension among persons aged ≥18 years was 29.6% (Table). Among persons aged ≥18 years with hypertension, the overall age-adjusted prevalence of blood pressure control was 48.0%. Substantial differences (relative difference >10%) in the prevalence of hypertension were indicated by age group, race/ethnicity, educational attainment, country of birth, family income, health insurance, diabetes, obesity, and disability status. The highest rates of hypertension were observed among those aged ≥65 years (71.6%), adults with diabetes (59.4%), and non-Hispanic black adults (41.3%). Although the difference in hypertension prevalence by sex was statistically significant, the difference was not substantial. Hypertension prevalence increased with age and decreased with increasing income level, but no significant trend was observed by educational attainment. Non-Hispanic blacks had a higher rate of hypertension (41.3%) than non-Hispanic whites (28.6%) and Hispanics (27.7%). Adults born in the United States had a higher rate of hypertension (30.6%) than non-U.S.-born adults (25.7%). Adults aged <65 years with public insurance had a higher rate of hypertension (28.3%) than those with private insurance (20.0%) and those with no insurance (20.4%). Persons with diabetes had a significantly higher rate of hypertension than those without diabetes (59.4% versus 27.7%), as did those who were obese compared with those who were not (40.5% versus 25.0%) and those with a disability compared with those with no disability (40.2% versus 29.0%).

Substantial differences in the prevalence of blood pressure control were observed among all population groups except veteran status. Among persons aged ≥18 years with hypertension, rates of blood pressure control were lowest among those without health insurance (27.9%), Mexican-Americans (30.3%), those who were never married (34.9%), and those born outside the United States (38.9%). Men, adults aged 18–44 years, Hispanics, Non-Hispanic blacks, those who were never married, non-U.S.-born, persons without health insurance had a lower prevalence of hypertension control than their counterparts. Men had a lower rate of hypertension control than women (42.7%). Adults aged 18–44 years had a lower rate of hypertension control (40.9%) than adults aged 45–64 years (53.3%) and 64 years and over (51.4%). The rate of controlled blood pressure was lower among Hispanics (34.4%) and non-Hispanic blacks (42.5%) than non-Hispanic whites (52.6%). Non-U.S.-born adults had a lower rate of hypertension control (38.9%) than U.S.-born adults (49.3%). Adults aged <65 years with no insurance had a lower rate of hypertension control (27.9%) than those with public insurance (60.2%) or private insurance (50.6%). Controlled hypertension was also lower among those classified as not obese compared with those who were obese (41.4% versus 54.0%), persons without diabetes compared with those with diabetes (45.4% versus 63.6%), and persons with no disability compared with those with a disability (45.0% versus 59.3%). Controlled hypertension was not linearly associated with age, educational attainment, or income level.

Discussion

The prevalence of hypertension has remained consistent over the past 10 years, at an overall rate of approximately 30% (1,13). During 2007–2010, the prevalence of hypertension by the analyzed demographic characteristics was highest among those aged ≥65 years (71.6%) and among non-Hispanic blacks (41.3%), two population groups known to be disproportionately affected (1,3,12). Although the overall prevalence of blood pressure control has improved over the past 10 years, non-Hispanic blacks and Hispanics continue to have lower prevalence of control than their non-Hispanic white counterparts (8,12). Also consistent with other research, the prevalence of hypertension was higher among those with diagnosed diabetes, obese persons, and persons with disabilities (3). However, all three of these groups had higher rates of blood pressure control than their counterparts in 2007–2010 (63.6%, 54.0%, and 59.3%, respectively, versus 45.4%, 41.4%, and 45.0% among those without diagnosed diabetes, obesity, and disabilities, respectively). This difference is likely because of higher rates of treatment with medication among these groups (5,14). In contrast, although the prevalence of hypertension was lowest among those aged 18–44 years (9.8%), the prevalence of blood pressure control was significantly lower among this group than their older counterparts. This is most likely because of lower rates of hypertension awareness and treatment with medication among younger adults (13,15).

Limitations

The findings in this report are subject to at least four limitations. First, NHANES data are restricted to the civilian noninstitutionalized population; thus, results from this study are not generalizable to persons who live in nursing homes, long-term care facilities, or prisons, or to military personnel. Second, reliable data were not available for persons of certain racial/ethnic groups or sexual orientation/gender identity. Only non-Hispanic blacks and Hispanics were oversampled; consequently, estimates cannot be calculated for other racial/ethnic populations (e.g., American Indians/Alaska Natives, Asians/Pacific Islanders). Third, the cross-sectional study design provides a one-time only assessment of blood pressure, although blood pressure can be measured multiple times during one visit. This one-time assessment can overestimate or underestimate hypertension prevalence. However, the standardized measurement of blood pressure in a mobile examination center makes NHANES the best source of national data on hypertension. Finally, this report does not examine time trends in disparities to assess progress toward eliminating disparities. Although other studies included time trends, only a limited number of demographic characteristics such as race/ethnicity, age, and sex were examined (10).

Conclusion

Consistent with the 2011 CHDIR and other studies, no change has occurred in the prevalence of hypertension over the last decade, although the rate of hypertension control continues to improve (2,3,10). Disparities in hypertension prevalence and control persist among most population groups assessed similar to what has been published elsewhere. Although rates of control have continued to show improvement (2,10), more time is needed to determine whether the population will meet Healthy People 2020 target of 61.2%. Certain subgroups of persons with hypertension exhibit even lower rates of blood pressure control, indicating a need for interventions that span the population and focus on vulnerable subgroups. The United States Preventive Services Task Force (USPSTF) recommends blood pressure screening for all adults aged ≥18 years, and as a result of provisions in the Patient Protection and Affordable Care Act (ACA), Medicare now covers certain adult clinical preventive services recommended by the USPSTF without patient cost sharing (§4103) (11,12). The law also requires that "nongradfathered" private health plans include these same services without cost sharing (§1001). In addition, the ACA ensures certain preventive and wellness services without cost-sharing for Medicare recipients (§4103), a group most in need of hypertension management. The national Million Hearts initiative endeavors to increase the number of persons in the United States whose hypertension is under control by 10 million, as part of its goal to prevent 1 million heart attacks and strokes by the year 2017. The Guide to Community Preventive Services Task Force recommends system interventions to improve blood pressure control, including clinical decision support systems, reducing out-of-pocket costs for CVD preventive services for patients with hypertension, and team-based care. Because the rate of blood pressure control is lowest among persons without health insurance, compared to those with insurance coverage, it will be important to monitor this and other vulnerable population groups in the future.

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