Response to Evaluating the True Prevalence of Resistant Hypertension
The National Health and Nutrition Examination Survey is a set of studies that were not specifically designed to determine the prevalence of true resistant hypertension in the US population. Accordingly, the estimates of the prevalence of resistant hypertension determined using the National Health and Nutrition Examination Survey data should be interpreted in the context of known, and previously stated, limitations.1 The white-coat effect, partial medication nonadherence, and inadequate medication dosage cannot be excluded, and, therefore, some individuals would have been falsely classified as having resistant hypertension. Using the average of the second and third blood pressure measurements obtained through a standardized research protocol may have reduced the white-coat phenomenon to some degree compared with what would be observed in a typical clinical setting but would not completely eliminate it. These limitations would lead to an overestimation of the prevalence of resistant hypertension. The inability to determine which individuals with uncontrolled blood pressure receiving ≤2 medications would still have uncontrolled blood pressure if treated with 3 agents would lead to an underestimation of the true prevalence.
Anyfanti et al2 raised a concern about whether secondary causes of hypertension were excluded. The goal of this analysis was to determine the prevalence of resistant hypertension and not the prevalence in the absence of secondary causes. Therefore, individuals who may have had secondary causes of resistance were not excluded. Furthermore, the National Health and Nutrition Examination Survey examinations did not include renin or aldosterone levels, timed sodium excretion, salt suppression testing, or diagnostic testing for sleep apnea, so these factors cannot be examined. NSAID use could be examined in a future study; however, it would not be possible with the National Health and Nutrition Examination Survey to distinguish infrequent and remote NSAID use from frequent use, and this limitation could falsely obscure an association between NSAID use and drug resistance if one were present. Because 87% of resistant adults were age ≥50 years and almost half were men, oral contraceptive use is unlikely to be a major contributor to the overall prevalence of resistant hypertension.
To their last point, whether outcomes for individuals with resistant hypertension are better when managed at specialized centers or within enhanced hypertension care delivery systems implemented in primary care settings is an empirical question that warrants future study.
Stephen D. Persell
Division of General Internal Medicine
Feinberg School of Medicine
Sources of Funding
S.D.P. was supported by career development award K08 HS015647 from the Agency for Healthcare Research and Quality.
Letters to the Editor will be published, if suitable, as space permits. They should not exceed 1000 words (typed double-spaced) in length and may be subject to editing or abridgment.
- © 2011 American Heart Association, Inc.