Control of Hypertension Among Adults — National Health and Nutrition Examination Survey, United States, 2005–2008

Paula W. Yoon, ScD1

Cathleen D. Gillespie, MS2

Mary G. George, MD2

Hilary K. Wall, MPH2

1Epidemiology and Analysis Program Office, Office of Surveillance, Epidemiology, and Laboratory Services

2Division for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion

Corresponding author: Paula W. Yoon, ScD, Office of Surveillance, Epidemiology, and Laboratory Services, CDC, 1600 Clifton Rd, NE, MS E-33, Atlanta, GA 30333. Telephone: 404-498-6298; Fax: 404-498-1111; E-mail: pay3@cdc.gov.

Introduction

Cardiovascular disease (CVD) is the leading cause of preventable death in the United States, and approximately 1 million heart attacks and 700,000 strokes occur annually (1). Hypertension is a major risk factor for cardiovascular disease and stroke; the unadjusted prevalence of hypertension among U.S. adults aged ≥18 years is approximately 31% (representing 68 million adults), and hypertension increases with age to approximately 70% among persons aged ≥65 years (2). Hypertension contributes to one out of every seven deaths in the United States, and approximately 70% of persons who have a first heart attack or stroke or who have heart failure have hypertension (1). In clinical trials, treatment of hypertension was associated with substantial reductions in stroke incidence (35%–40%), myocardial infarction (20%–25%), and heart failure (>50%) (3). The estimated annual direct costs of hypertension are approximately $69.9 billion, and the estimated annual indirect costs are $23.6 billion (4).

Hypertension is defined as having a systolic blood pressure of ≥140 mm Hg or a diastolic blood pressure of ≥90 mm Hg (5). The U.S. Preventive Services Task Force guidelines for the prevention of hypertension call for hypertension screening in adults aged ≥18 years (a grade A recommendation: strongly recommended) (6). The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC7) recommended screening every 2 years in persons with blood pressure of <120/80 mm Hg and every year for those with a systolic blood pressure of 120–139 mm Hg or diastolic blood pressure of 80–89 mm Hg (5). Once treatment has been initiated in patients identified with hypertension, monthly follow-up and adjustment of medications is recommended until the blood pressure goal is reached. Because the relationship between systolic blood pressure and diastolic blood pressure and cardiovascular risk is continuous and graded, the actual level of blood pressure elevation should not be the sole factor when making treatment decisions. Clinicians also should consider the patient's overall cardiovascular risk profile, including smoking, diabetes, abnormal blood lipid values, age, sex, sedentary lifestyle, and obesity (5). In addition to pharmacologic therapy for hypertension control, nonpharmacologic therapies (e.g., reduction of dietary sodium intake, potassium supplementation, increased physical activity, weight loss, and reduction of alcohol intake) are associated with a reduction in blood pressure (7). This report analyzes 2005–2008 data from the National Health and Nutrition Examination Survey (NHANES) to determine the prevalence of hypertension treatment and control among U.S. adults. Public health authorities and clinicians can use these data to identify population subgroups that might require additional strategies to access preventive services needed to control hypertension.

Methods

To estimate the percentage of adults aged ≥18 years with hypertension whose blood pressure is under control, CDC analyzed data from NHANES from two survey cycles: 2005–2006 and 2007–2008. NHANES is a complex, multistage probability sample of the noninstitutionalized U.S. population.* Mobile examination center response rates for NHANES during the study period were 76%.† A total of 11,154 participants aged ≥18 years were interviewed and examined. An average of up to three blood pressure measurements was obtained under standard conditions as part of a single physical examination at a mobile examination center. Women who were pregnant or whose pregnancy status could not be determined (n = 505) were excluded, as were participants who did not have complete data to determine hypertension status (n = 601) or who were missing covariates of interest (n = 66). Some participants were excluded on the basis of more than one criteria, yielding an eligible sample of 10,043 persons; of these, 3,567 (35.5% unweighted) had hypertension and were included in this analysis.

Approximately 95% of the participants had two or three complete blood pressure measurements. Hypertension was defined as having an average systolic blood pressure of ≥140 mmHg, an average diastolic blood pressure of ≥90 mmHg, or self-reported current use of blood pressure–lowering medication. Treatment of blood pressure was defined as the self-reported current use of blood pressure–lowering medication, and its prevalence was calculated among all those defined as having hypertension. Blood pressure control was defined as having an average systolic blood pressure of <140 mmHg and diastolic pressure of <90 mmHg, and its prevalence was calculated among all those defined as having hypertension. Blood pressure control among persons who were treated was defined as an average systolic blood pressure of <140 mmHg and diastolic pressure of <90 mmHg, and its prevalence was calculated among persons who self-reported current use of blood pressure–lowering medication. Hypertension treatment, control, and control among treated estimates were analyzed by diagnosed diabetes and chronic kidney disease (CKD)status and by certain demographic characteristics (i.e., sex, age group, race/ethnicity, poverty-income ratio,§ education level, health insurance status,¶ having a usual source of medical care,** the number of times medical care was received in the previous year,†† and the type of place most often visited for health care§§). Diagnosed diabetes is based on a participant's positive response to the question, "Other than during pregnancy, have you ever been told by a doctor or health professional that you have diabetes or sugar diabetes?" CKD was defined as estimated glomerular filtration rate of <60 mL/min/1.73 m2 calculated or albumin-creatinine ratio of ≥30 mg/g (8). Participants with missing data for CKD were assumed to be negative. All analyses were conducted by using statistical software to account for sampling weights and to adjust variances for the multistage, clustered sample designs. Estimates for prevalence of hypertension were standardized to the age distribution of the 2000 U.S. standard population, based on the following age groups: 18–29, 30–39, 40–49, 50–59, 60–69, 70–79, and ≥80 years. Estimates of treatment and control among those with hypertension and control among those treated were standardized to the age distribution of the 2000 U.S. standard population, based on the following age groups: 18–49, 50–59, 60–69, 70–79, and ≥80 years.

To assess trends over time for the prevalence of hypertension, treatment, control, and control among treated, CDC analyzed data from the most recent five available NHANES cycles (1999–2000, 2001–2002, 2003–2004, 2005–2006, and 2007–2008). Estimates from single cycles were standardized to the age distribution of the 2000 U.S. standard population based on the following age groups: 18–39, 40–59, 60–74, and ≥75 years. Logistic regression models, adjusted for sex, age group, and race/ethnicity, were used to test for statistically significant trends over time. Tests were considered statistically significant at the p<0.01 level.

Results

The findings indicate that prevalence of hypertension in U.S. adults did not change significantly from 1999–2000 (28.7%) to 2007–2008 (29.5%) (p = 0.41). However, the prevalence of treatment, control among all persons with hypertension and control among persons taking blood pressure–lowering medication increased during the 10-year period 1999–2008 (Figure).

During 2005–2008, the age-standardized prevalence of hypertension among U.S. adults was approximately 29.3%. The prevalence of hypertension among persons with diabetes or CKD was 42.9%. Persons with diabetes or CKD accounted for 24.6% of U.S. adults with hypertension. Among all persons with hypertension, the age-standardized estimated prevalence of pharmacologic treatment during 2005–2008 was 61.7% (Table). Control of hypertension among all persons with hypertension was 43.6%, and control was 71.7% among persons who reported that they were currently taking blood pressure–lowering medication. The prevalence of treatment was lower among persons without diabetes or CKD (58.9%) compared with those with diabetes or CKD (70.8%). The prevalence of treatment was lowest among males (54.9%), persons aged 18–39 years (37.4%), Mexican-Americans (45.3%), those without a usual source of medical care (19.3%), those who reported receiving medical care less than twice during the previous year (27.2%), those who reported being uninsured (41.9%), and those who reported usually receiving care at a hospital emergency room or other location (26.3%). The prevalence of control was lowest among males (38.8%), persons aged 18–39 years (31.4%), Mexican-Americans (32.0%), those without a usual source of medical care (10.8%), those who received medical care fewer than two times in the previous year (17.1%), those who reported being uninsured (26.5%), and those who reported usually receiving care at a hospital emergency room, other location or none (16.7%). The prevalence of control among persons who were treated was lowest among persons with diabetes or CKD (60.3%) compared with persons without these conditions and among persons aged ≥65 years (58.8%) (Table).

Discussion

The results of this analysis demonstrate that while the prevalence of hypertension remained flat at approximately 30% during 1999–2008, the prevalence of hypertension treatment and control increased steadily during the 10-year period. Despite this progress, prevalence of treatment, control among all persons with hypertension, and control among persons who were treated are lower among certain subgroups of the population. Persons aged 18–39 years had the lowest prevalence of treatment and control compared with persons aged ≥40 years, but younger persons who reported that they were currently taking hypertension medications had the highest control levels (84.1%) among the three age groups surveyed. Persons with diabetes or CKD had a higher prevalence of treatment compared with those without these conditions (70.8% versus 58.9%), but control among persons who were treated was lower for persons with diabetes or CKD (60.3% versus 76.0%). Control rates for persons with diabetes or CKD would have been even lower if control were defined as <130/80 mm Hg for these groups at high risk for CVD as recommended by the American Diabetes Association and the National Kidney Foundation (9,10). Persons with diabetes or CKD might visit a clinician more frequently and are likely to be under treatment for hypertension as part of their chronic care management, but the complexity of the multiple comorbidities might make the hypertension more difficult to control.

The most disadvantaged persons in terms of treatment and control are those with no usual source of health care, those who received medical care fewer than two times in the previous year, those who were uninsured, and those who reported usually receiving care at a hospital emergency room, receiving care at some other location, or not receiving care. However, despite low levels of treatment and control for persons without regular access to primary health care, those who reported that they were taking hypertension medications currently achieved levels of control similar to persons who had regular access to primary care. On the basis of this analysis, approximately 18 million adults with hypertension have no usual source of care, receive care fewer than two times per year, are uninsured, or usually receive care at an emergency room or other location, representing 37% of the adult population with hypertension.

Impending changes in the U.S. health-care system offer opportunities to increase prevalence of preventive services to control hypertension. The Patient Protection and Affordable Care Act of 2010 (as amended by the Healthcare and Education Reconciliation Act of 2010 and referred to collectively as the Affordable Care Act [ACA]) expands insurance coverage, consumer protections, and access to primary care (11,12). The law expands Medicaid to cover persons with incomes up to 133% of the federal poverty level (ACA §2001). Starting in 2014, state-based insurance exchanges††† will provide access to health insurance for small employers and to persons and families not eligible for Medicaid or the Children's Health Insurance Program, and federal tax credits will help those living at 100%–400% of the federal poverty level (ACA §1311). The Affordable Care Act also provides for guaranteed issue of insurance, ending denials of coverage for preexisting conditions (hypertension is considered a preexisting condition by certain insurers) (ACA §1201), and prohibits rescission (dropping coverage), lifetime coverage limits, and limits on emergency room use. The law also expands access to primary care by increasing funding to community health centers, which provide primary health-care services to uninsured and underserved populations (ACA §5601.) The primary care workforce will be strengthened through provisions that increase funding for the National Health Service Corps to increase the number of providers in underserved areas; provide incentives to expand the number of primary care physicians, nurse practitioners, and physician assistants; and offer scholarships and loan repayments for those working in underserved areas. Increasing access to primary care and increasing the proportion of persons with a usual care provider can lead to better diagnosis, treatment, and control of hypertension.

Hypertension screening in adults aged ≥18 years is a grade A recommendation from USPSTF (6) and therefore is covered without cost sharing as of January 1, 2011, by Medicare (ACA §4104) and will be covered by the new health exchanges that go into effect starting in 2014 (ACA §1001). Beginning January 1, 2013, state Medicaid programs that offer U.S. Preventive Services Task Force grade A or B services at no cost sharing will receive an enhanced federal matching rate. Currently, the U.S. Preventive Services Task Force has not given a grade A or B recommendation to existing clinical guidelines for hypertension treatment and management, which means that hypertension treatment and management are subject to cost sharing. However, provisions of the Affordable Care Act might reduce patient out-of-pocket costs for clinician visits and hypertension medications. These include an essential health benefits package (ACA §1302) that limits cost sharing and includes preventive and wellness services, prescription drugs, and chronic disease management. Each state will determine which evidenced-based clinical services will be included in the state's essential health benefits package. Clinical services for controlling hypertension (e.g., team-based coordination of care and reducing or eliminating cost-sharing for medications and other services such as lifestyle counseling) might be beneficial because studies indicate that hypertension control is one of the preventive services with the greatest potential for preventing deaths (13–15).

Persons aged ≥65 years accounted for 38% of persons with hypertension in this study. For such persons, the Affordable Care Act makes several changes to Medicare Part D to reduce patient out-of-pocket costs for prescription drugs. In 2010, Medicare beneficiaries who reached the coverage gap (the difference of the initial coverage limit and the catastrophic coverage) in expenses were eligible to receive a $250 rebate from Medicare. Beginning in 2011, Medicare beneficiaries reaching the coverage gap will be given a 50% discount on the total cost of brand name drugs while in the gap and pay a reduced rate for generic medications. Medicare will phase in additional discounts on the cost of both brand name and generic drugs. By 2020, these changes will effectively close the coverage gap and rather than paying the full cost of prescription drugs while in the gap, a senior's responsibility will be 25% of the costs (16).

The American College of Cardiology and the American Heart Association recommend that patients have a comprehensive cardiovascular health assessment at least every 5 years starting at age 18 years, and that those with cardiovascular risk factors such as diabetes or hypertension or those who smoke cigarettes should have their cardiovascular health risk assessed more frequently (17). A health risk assessment is provided for in the annual wellness visit for Medicare, as are counseling services aimed at reducing risk factors for chronic disease, including hypertension, heart disease, and stroke (ACA §4103). In December 2011, CDC issued a framework for patient-centered health risk assessments for persons aged ≥65 years (18).

The management of hypertension is also likely to benefit from provisions of the Affordable Care Act that call for improving health-care quality and making system-level changes to health-care delivery. The National Strategy to Improve Health Care Quality (ACA §3011) calls for promoting the most effective prevention and treatment practices for the leading causes of mortality, starting with CVD, and includes efforts to decrease preventable hospitalizations and readmissions (19). Hospitalization for hypertension, also referred to as an ambulatory-care–sensitive condition, is preventable; such hospitalization could be avoided if patients were to receive early and continued access to quality health care (20). Other quality improvement initiatives that might promote treatment according to guidelines for hypertension control include the Physician Quality Reporting System (ACA §3002), the development of quality measures (ACA §3013) and meaningful use of clinical data (21), incentives for physicians to join accountable care organizations to better coordinate patient care and improve quality, creation of community health teams that can coordinate prevention and disease management and support primary care providers (ACA §3502), and the development of medication management services by pharmacists that can increase patient adherence to prescribed medications (ACA §3503). Quality improvement efforts that improve the care of patients with hypertension can have substantial public health impact because even small improvements in blood pressure control can reduce the risk of cardiovascular disease. Health system changes might be of particular value to persons with hypertension who also have diabetes or CKD as the complexity of the therapeutic regimes for these patients might benefit from better coordinated disease management. In September 2011, as part of national health quality improvement efforts, the U.S. Department of Health and Human Services launched the Million Hearts national initiative (22) to prevent 1 million heart attacks and strokes over the next 5 years. Led by CDC and the Centers for Medicare and Medicaid Services, the Million Hearts initiative aims to improve heart disease and stroke prevention by improving access to effective care, improving the quality of care, focusing more clinical attention on heart attack and stroke prevention, increasing public awareness of how to lead a heart-healthy lifestyle, and increasing the consistent use of high blood pressure and cholesterol medications.

Improving the management of hypertension will require further efforts. For example, standardization of health information technology that allows exchange of clinical data between health-care providers could increase awareness of hypertension diagnosis and control among all of a patient's providers. Adoption of electronic health records that include decision support tools that prompt clinicians to ask patients about medication adherence also could improve the management of hypertension (23). Barriers to hypertension medication adherence should be addressed (e.g., costs, health literacy, lack of perceived benefit, and multiple comorbidities) and nonpharmacologic approaches that can reduce blood pressure should be emphasized (e.g., adoption of a healthy diet that includes reduction of dietary sodium intake, increased physical activity, weight loss, smoking cessation, and reduction of alcohol intake) (7).

The findings in this report are subject to at least three limitations. First, the population of persons with hypertension in this study might underestimate the U.S. population of persons with hypertension because older persons residing in nursing homes and other institutions, who have a higher prevalence of age-related hypertension, are not included in NHANES. Second, although data collection is standardized, NHANES self-reported data on the use of blood pressure medications and diagnosis of diabetes from interviews and questionnaires are subject to inaccuracies or recall bias. Finally, the estimated prevalence of adults with hypertension might be underestimated because only persons who had measured high blood pressure during the examination and those who reported taking pharmacologic treatment to achieve control of hypertension were included in the analysis. Certain participants who might have received a diagnosis of hypertension previously but who had normal blood pressure measurements during the examination, perhaps as a result of life-style habits (e.g., diet and exercise), were not included as having hypertension in the analysis.

Conclusion

Hypertension control has the potential to prevent a substantial number of deaths because although hypertension is common (affecting approximately 30% of the U.S. adult population), therapeutic interventions are effective, and control rates are below achievable levels (13). If implementation of health-care reform increases the number of people with regular access to primary care and access to affordable medications, it could have a substantial impact on control of hypertension in the U.S. population.

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