Sex- and Ethnic Differences in the Cross-sectional Association Between Sleep Regularity and Obesity Among US Adults, NHANES 2011-2014

Obesity is a major public health concern, with disparities across racial and sex groups. While sleep duration has been extensively studied in relation to obesity, the role of sleep regularity remains less explored. In 2 nationally representative samples of US adults in the National Health and Nutrition Examination Survey (NHANES 2011/2012 & 2013/2014, <i>n</i> = 7085), we investigated the cross-sectional association between a sleep regularity index (SRI) derived from accelerometer data and obesity measures. Body mass index (BMI), waist circumference (WC), body roundness index (BRI), total fat mass, sagittal abdominal diameter (SAD), sagittal abdominal diameter to height ratio (SADHtR), fat mass index (FMI), lipid accumulation product (LAP), and visceral adiposity index (VAI) were derived from NHANES body measures. Multivariable-adjusted regression models were used to estimate multiplication factors (MF) and 95% confidence intervals (CIs) comparing mean BMI across quintiles of SRI and to test for effect modification by sex and ethnicity. Higher SRI was associated with significantly lower BMI (MF SRI_Q5vs.Q1: 0.92; 95% CI, 0.91-0.94; <i>P</i>_trend < 0.001), translating into 8% lower BMI among those with most versus least regular sleep. This association was more pronounced among women than men (MF SRI_Q5vs.Q1 women: 0.92; 95% CI, 0.90-0.95; men: 0.98; 95% CI, 0.96-1.00), with strongest effects in non-Hispanic White and other/multi-racial women (<i>P</i>_interaction < 0.001). Similar inverse associations were observed for all other obesity measures. In conclusion, sleep regularity, measured by the SRI, was inversely associated with BMI and any other obesity measures. The observed disparities suggest sleep regularity may contribute differentially to obesity risk by sex and race/ethnicity.