Abstract P316: The Mediation of Racial Differences in Hypertension by Sleep Characteristics: Chicago Area Sleep Study
Introduction: There are disparities in hypertension prevalence by race/ethnicity in the United States. Given differences in sleep by race and the association between sleep characteristics and hypertension, we examined whether racial differences in hypertension were partially mediated by differences in sleep.
Methods: The Chicago Area Sleep Study (CASS) is a cross-sectional study of 155 black, 129 white, 103 Hispanic and 109 Asian men and women ages 35-64 who had an apnea/hypopnea index<15 determined during 1 night of screening (ApneaLinkTM). Participants wore wrist actigraphs for 7 days (ActiwatchTM) to determine sleep characteristics. The total sleep interval was determined using the Actiwatch event marker or sleep log and sleep % was calculated as duration (determined by actigraphy) /total sleep interval. Blood pressure was measured 3 times after 5 minutes rest; hypertension was determined according to JNC-VII 2010 criteria. To examine mediation, we used the approach and SAS macro developed by Valeri and VanderWeele and fitted two models; a Poisson regression model for hypertension and a linear regression model for sleep characteristic. From these combined models, we estimated the prevalence ratios for natural direct effects (PRNDE) of race on hypertension, natural indirect effects (PRNIE) (mediated by sleep characteristics), and total effect (PRTE). We also calculated the proportion of the total effects that were mediated by sleep characteristics.
Results: Participants’ mean age was 47.8 years. Sleep duration was longest in whites 445 min (SD=53min), followed by Asians 413 min (SD=51 min), Hispanics 417 min (SD=79 min) and Blacks 409 min (SD=67 min). Average sleep percentage was 92% (SD=4%) in whites, 88% (SD=5%) in Blacks, 91% (SD=5%) in Asians, and 90% (SD=4%) in Hispanics. In models adjusted for age, race, sex, education, smoking status, alcohol intake, physical activity, depressive symptoms and work schedule the direct effect (prevalence ratio) of race on hypertension was 4.6 for Blacks vs. whites, 1.5 for Asians vs. whites and 2.2 for Hispanics vs. whites. The indirect effects (mediated by sleep percentage) for the three groups were 1.19, 1.06, and 1.05 respectively, suggesting that sleep percentage mediated 10 % of the difference in prevalence for hypertension between Blacks and whites, 10% of the difference between Asians and whites and 7 % of the difference between Hispanics and whites. In contrast, there was no evidence that sleep duration mediated the race differences in hypertension.
Conclusions: While sleep duration did not contribute to race differences in hypertension prevalence, sleep percentage, which may reflect quality of sleep, may contribute to racial differences in rates of hypertension.
Author Disclosures: L. Rasmussen-Torvik: None. P. de Chavez: None. K. Kershaw: None. K. Knutson: None. K. Kim: None. P. Zee: None. M. Carnethon: None.
- © 2016 by American Heart Association, Inc.