Psychosocial Factors and Racial Differences in Blood Pressure Dipping

It is becoming increasingly well known that abnormal diurnal blood pressure (BP) patterns are powerful predictors of cardiovascular morbidity and mortality independent of office-measured BP and other established cardiovascular risk factors.1 What is less well known, is why certain subgroups of the population tend to have disproportionately higher levels of nighttime BP and reduced BP dipping. Black populations in the United States have been found to have higher rates of hypertension and cardiovascular–renal complications as compared to other racial or ethnic populations.2 A number of previous studies have also demonstrated that blacks are significantly more likely to have a blunted nocturnal BP decline (typically defined as a nocturnal BP <10% of mean daytime BP) as compared with nonblacks.3 In this issue of American Journal of Hypertension, Spruill et al. present their interesting work which highlights the importance of psychosocial and socioeconomic factors in explaining part of the well-documented racial differences in BP dipping.4 The study shows that in a cross-sectional analysis of 171 black and white normotensive and mildly hypertensive participants, higher education, higher income, being married, and higher perceived social support, are each associated with increased BP dipping. Notably, marital status and education together accounted for 36% of the effect of race on dipping. The main strengths of this study were the use of three ambulatory BP monitoring (ABPM) sessions to determine dipping status, and the use of multiple validated measures of psychosocial factors. An important limitation is the cross-sectional design, which precludes making any inferences regarding causality. The mechanisms underlying an abnormal nighttime BP-dipping pattern are not fully understood. Several demographic, physiological, and psychosocial factors, (including age, sodium sensitivity, postmenopausal status, sleep apnea, and poor sleep quality), appear to have an association with a nondipping BP pattern. Our previous report, based on the analysis of a controlled feeding trial, demonstrated that even when controlling for traditional lifestyle factors that influence BP levels, specifically diet, blacks demonstrated a significant, blunted nocturnal decline in BP as compared to nonblacks.5 Most previous studies, which have attempted to examine the influence of psychosocial factors (such as increased anger, hostility, depression, and stress) on BP dipping, have been limited by small sample sizes or the inability to examine multiple psychosocial variables simultaneously. The findings by Spruill et al. add valuable knowledge to the existing body of literature focusing on understanding racial differences in BP dipping. This work reinforces the potential importance of behavioral risk factors on long-term cardiovascular health. Future prospective studies will be needed to confirm these observations and to disentangle the relative contributions of genetic, behavioral, and other environmental factors responsible for the ethnic differences in diurnal BP patterns. It remains to be seen whether implementation of ABPM in primary care, increased emphasis on 24-h BP control, and stress reduction techniques may have important therapeutic implications for hypertension management. The author declared no conflict of interest.