Prevalence of Masked Hypertension Among US Adults With Nonelevated Clinic Blood Pressure

Abstract

Masked hypertension (MHT), defined as nonelevated blood pressure (BP) in the clinic setting and elevated BP assessed by ambulatory monitoring, is associated with increased risk of target organ damage, cardiovascular disease, and mortality. Currently, no estimate of MHT prevalence exists for the general US population. After pooling data from the Masked Hypertension Study (n = 811), a cross-sectional clinical investigation of systematic differences between clinic BP and ambulatory BP (ABP) in a community sample of employed adults in the New York City metropolitan area (2005-2012), and the National Health and Nutrition Examination Survey (NHANES; 2005-2010; n = 9,316), an ongoing nationally representative US survey, we used multiple imputation to impute ABP-defined hypertension status for NHANES participants and estimate MHT prevalence among the 139 million US adults with nonelevated clinic BP, no history of overt cardiovascular disease, and no use of antihypertensive medication. The estimated US prevalence of MHT in 2005-2010 was 12.3% of the adult population (95% confidence interval: 10.0, 14.5)-approximately 17.1 million persons aged ≥21 years. Consistent with prior research, estimated MHT prevalence was higher among older persons, males, and those with prehypertension or diabetes. To our knowledge, this study provides the first estimate of US MHT prevalence-nearly 1 in 8 adults with nonelevated clinic BP-and suggests that millions of US adults may be misclassified as not having hypertension.

Keywords: ambulatory blood pressure; blood pressure; masked hypertension; multiple imputation; prevalence.

Figure 1.

Estimated prevalence of masked hypertension in the United States, by age, 2005–2010. Estimates were based on multiple imputation (500 data sets) of hypertension status as defined by ambulatory blood pressure for 9,316 adult participants in the National Health and Nutrition Examination Survey (2005–2010) with nonelevated clinic blood pressure, no history of overt cardiovascular disease, and no use of antihypertensive medication. A locally weight scatterplot smoothing (LOESS) curve using second-degree polynomials (black line) was fitted to the 65 age-specific estimates (black circles), with weights proportional to the inverse of each estimate's squared standard error; the smoothing parameter (1.00) was selected to optimize the generalized cross-validation criterion (36). Gray area, 95% confidence interval.

Figure 2.

Estimated prevalence of masked hypertension according to clinic blood pressure (BP) in the United States, 2005–2010. A) Systolic BP; B) diastolic BP. Estimates were based on multiple imputation (500 data sets) of hypertension status as defined by ambulatory blood pressure for 9,316 adult participants in the National Health and Nutrition Examination Survey (2005–2010) with nonelevated clinic BP, no history of overt cardiovascular disease, and no use of antihypertensive medication. A locally weight scatterplot smoothing (LOESS) curve using second-degree polynomials (black line) was fitted to the 50 BP-specific estimates (black circles), with weights proportional to the inverse of each estimate's squared standard error; smoothing parameters (1.00 for part A, 0.73 for part B) were selected to optimize the generalized cross-validation criterion (36). Gray area, 95% confidence interval.