NHANES Data Highlight the Clinical Characteristics of Those With Poorly Controlled Hypertension


Michael J. Bloch, MD, MedSchool Associates North, University of Nevada School of Medicine, 1500 East Second Street, Suite 302, Reno, NV

Longitudinal data from the National Health and Nutrition Examination Surveys (NHANES) demonstrate that during the years 1998–2008, the prevalence of uncontrolled hypertension has declined. However, there is still considerable room for improvement because in 2007–2008, 49.9% of hypertensives, representing approximately 33 million Americans, did not have adequate blood pressure (BP) control (<140/90 mm Hg). The largest group of patients with poorly controlled hypertension were those who remained untreated (52.2% in 2005–2008). The second largest group were those who were treated with only 1 or 2 antihypertensive medications (34.4% in 2005–2008). Apparent treatment-resistant hypertension, defined as poor control despite at least 3 antihypertensive medications, was the third largest group and found in 28.0% of uncontrolled hypertensives between 2005–2008, an increase from past evaluations. These data demonstrate that the majority of patients with uncontrolled hypertension are usually untreated or undertreated and not necessarily resistant to treatment. Future population-based strategies to improve BP control needs to focus on improving access to care and raising awareness of hypertension in those who infrequently seek primary care. In addition, overcoming therapeutic inertia by adding antihypertensive medications and intensifying treatment appears important if we are to further improve BP control.

Study Methods

Between 1988 and 2008 a series of surveys of the US population was undertaken by the Centers for Disease Control and Prevention. Known as NHANES, these surveys used stratified multistage probability sampling on the noninstitutionalized US population who were asked to self-report information about a number of chronic medical conditions and health-related behaviors. In addition, each participant had their BP measured in standardized fashion by trained study personnel and had basic laboratory studies performed, including lipid panels, measurement of renal function, and fasting blood glucose. Hypertension was defined as a systolic BP at least 140 mm Hg, a diastolic BP at least 90 mm Hg, or a positive response to the question “Are you currently taking medication to lower your BP.” Awareness, current treatment of hypertension, and number of medications were all self-reported on the basis of standard queries. Control of hypertension was defined as a systolic BP <140 mm Hg and a diastolic BP <90 mm Hg.

Therapeutic inertia was arbitrarily defined and stratified according to prespecified criteria that took into account the level of BP control, the number of health care provider visits in the past year, the number of medications being taken, and the underlying cardiovascular risk. Because medication dose and adherence to therapy is not captured in NHANES, the term apparent treatment resistant hypertension (aTRH) was used and defined as uncontrolled hypertension despite the use of at least 3 antihypertensive medications. The investigators focused on those with uncontrolled hypertension and identified 3 key groups: (1) untreated hypertensives, (2) hypertensives taking 1 or 2 medications, and (3) aTRH. The authors used standard statistical tools to identify key characteristics that were significantly associated with each group.—Egan BM, Zhao Y, Axon RN, et al. Uncontrolled and apparent treatment resistant hypertension in the United States 1998 to 2008. Circulation. 2011;124:1046–1058.

Study Results and Commentary

Overall, the proportion of patients with uncontrolled hypertension declined from 72.2% in 1988–1994 to 52.5% in 2005–2008. Across all time periods, male sex, black race, and Hispanic ethnicity were associated with poor BP control. Uncontrolled hypertensives were more likely to have only 0 or 1 health care visits annually, while controlled hypertensives were more likely to have at least 4 health care visits per year. Among patients with uncontrolled hypertension, the proportion of uninsured patients increased over time. Additionally, the prevalence of diabetes was higher in controlled rather than uncontrolled patients. These data suggest that having an identified reason to access health care, both in terms of expanding insurance coverage and requiring a greater frequency of contacts with a health care provider, has an impact on improving BP control.

Focus on Untreated Hypertension

The likelihood of being treated for hypertension rose steadily from 1988–2008, but even in 2005–2008, more than 50% of uncontrolled patients were untreated. Roughly two thirds of these untreated hypertensives were unaware of their condition. The particular design of the NHANES, where hypertension was often defined based on BP readings from a single study visit, may have overestimated the incidence of hypertension and particularly untreated hypertension. Nonetheless, even taking this into account, it would appear that lack of treatment (and even awareness) of hypertension is the most common reason for poor BP control.

Among this group of untreated hypertensives, infrequent contact with a health care provider was a major issue as approximately 40% reported having 0 or 1 visits to a health care provider annually. Furthermore, many patients with hypertension lack insurance and cannot afford the visits to a health care provider and/or the cost of antihypertensive medications. In addition, since hypertension is largely an asymptomatic condition, even people with access to affordable health care without other medical issues that often prompt health care screening, such as young men, may not have their BP measured regularly.

In summary, these data suggest that changes in public health policy and health care delivery could lead to substantial improvements in BP control. In addition to expanding health insurance coverage and access to affordable medications, increased BP screenings, particularly in less traditional settings where young men are more likely to gather (ie, work sites, barbershops, grocery stores, pharmacies) and public health campaigns focusing on the importance of BP measurement and control may be among the most important and cost-effective ways to improve BP control rates.

Focus on Treated Hypertensives Treated With 1 or 2 Antihypertensive Medications

The second largest group of uncontrolled hypertensives in NHANES were those treated with only 1 or 2 medications, representing about one third of the total in each of the NHANES examination time periods. By definition, this group of patients has inadequately treated hypertension. Whereas infrequent contact with a health care provider was a frequent characteristic of those with untreated hypertension, in this group treated with only 1 or 2 medications, 85% to 90% had at least 2 visits annually with a provider.

These data suggest that therapeutic inertia, the failure to intensify therapy in the face of poorly controlled hypertension, appears to be the primary driving force in this group. Degree of therapeutic inertia, as defined somewhat arbitrarily for the purposes of this study, was found in more than 50% of these patients.

The authors of this report suggest that therapeutic inertia is not a provider-only trait, but a reflection of the provider-patient interaction. We believe it is really the result of the complex interactions between patient, provider, and other components of the health care delivery system, including health plans, formularies, pharmacies, and governmental agencies. Multiple studies have identified that therapeutic inertia is a major contributor to poor BP control, and awareness of the issue to date does not appear to have led to major improvements in control. In order to better overcome therapeutic inertia, we need to work towards developing systems of care that appropriately align incentives across the spectrum of health care delivery and award quality. Overcoming therapeutic inertia (ie, intensifying therapy in the setting of poorly controlled hypertension) should be considered a variable in emerging pay-for-performance models.

Focus on Apparently Treatment-Resistant Hypertension

Although definitions vary, resistant hypertension is generally defined as uncontrolled hypertension in the setting of at least 3 well-chosen, adequately dosed medications or BP that is controlled using at least 4 medications. Since the NHANES database has only limited data regarding antihypertensive medication adherence and dose, it is not possible to adequately define the exact proportion of patients who are treatment-resistant, hence the use of the term apparent treatment resistant. Over time, the proportion of uncontrolled patients with aTRH increased from 15.9% in 1988–1994 to 28.0% in 2005–2008. In actuality, many of these patients may have the white-coat effect or poor adherence rather than true treatment resistance.

While it appears to be less common than untreated or inadequately treated hypertension, aTRH remains an important issue. Other studies have demonstrated that these patients are at significant risk for cardiovascular events and may gain substantial clinical benefit from improved BP control. In multivariate analyses, clinical factors associated with aTRH-apparent, treatment-resistant hypertension in NHANES include infrequent health care visits and the presence of obesity, chronic kidney disease, or a high Framingham risk score. One particular issue that was highlighted in this paper is the infrequent use of spironolactone in this patient population.

Hopefully, the Eighth Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC 8) will provide clinicians with more comprehensive guidance on how to better use appropriate combinations of antihypertensive medications in patients with poorly controlled hypertension. Additionally, the continued development of novel device interventions aimed at treatment-resistant hypertension, including baroreceptor modulation and renal sympathetic denervation, may prove beneficial.

Final Thoughts

The NHANES investigators have provided us with a relatively complete snapshot of what the population of patients with poorly controlled hypertension look like. It is now up to us as clinicians and policy makers to develop the best strategies to improve BP control based on these findings.