Gender-specific Association of Sleep Duration with Body Mass Index, Waist Circumference, and Body Fat in Chinese Adults

Objective To examine the association between habitual sleep duration and obesity among Chinese adults. Methods The association of sleep duration and obesity was investigated among 7,094 community-dwelling Chinese adults. Sleep duration was self-reported. In this study, obesity was defined as follows： body mass index （BMI） ≥ 28 kg/m^2, waist circumference （WC） ≥ 85 cm in men and ≥ 80 cm in women, and percent body fat （%BF） ≥ 25 in men and ≥ 35 in women. Logistic and quantile regressions were employed to examine relationships of interest. Results Overall, 6.42% of the participants reported short sleep durations （〈 6 h/d） while 14.71% reported long （≥ 9 h/d） sleep durations. Long sleepers （≥ 9 h/d） represented a greater frequency of women with obesity [odds ratio （OR）： 1.30; 95% confidence interval （CI）, 1.02-1.67] and high body fat （1.43, 1.04-1.96） than those who slept 7-8 h/d. An association between long sleep times and higher BMI estimations was found across the 10th-75th percentile of the BMI distribution. Among men, long sleepers （≥ 9 h/d） presented lower risks of developing abdominal obesity compared with individuals who slept 7-8 h/d （OR = 0.79, 95% CI： 0.44-0.99）. Conclusion Our study suggests that long sleep durations are associated with general obesity in Chinese women but reduced waist circumferences in men. Confirmatory studies are needed to determine the heterogeneous association of sleep time and obesity by gender.