Short sleep duration in association with CT-scanned abdominal fat areas: the Hitachi Health Study.

OBJECTIVE: To examine the relationship between short sleep duration and body mass index (BMI), waist circumference (WC), visceral fat area (VFA) and subcutaneous fat area (SFA) among a working population in Japan.

DESIGN: Health-center-based, cross-sectional study.

SUBJECTS: The study subjects included 5400 men and 642 women aged 30 to 75 years who underwent an abdominal computed tomography (CT) scanning examination in a comprehensive health checkup.

MEASUREMENTS: Height and weight were measured, and BMI was calculated. WC, VFA and SFA were measured using a CT scanner. Sleep duration was self-reported. Analysis of covariance was used to estimate adjusted means of BMI, WC, VFA and SFA across categories of sleep duration with adjustments for potential confounders. Trend of the association was assessed using multiple linear regression analysis.

RESULTS: In men, the mean values of BMI, WC and SFA decreased with increasing sleep duration after adjustment for age, physical activity, smoking and drinking (P-value for trend <0.001). Additional adjustment for physical illnesses did not attenuate the explanatory power of the models (P-value for trend <0.001). In addition, the association between sleep duration and SFA did not change after controlling for VFA (P-value for trend <0.001). The mean values of SFA for subjects sleeping '<5 h', '5 to <6 h', '6 to <7 h' and '7 h' per day were 145.8±67.4 cm(2), 138.7±61.5 cm(2), 134.7±60.4 cm(2) and 132.5±49.2 cm(2), respectively. Sleep duration was not appreciably associated with VFA. In women, no significant association was detected in any models.

CONCLUSION: Shorter sleep duration is associated with higher BMI, WC and SFA in men. Further research is needed to explicate the biological mechanisms behind these relationships and to see whether interventions addressing inadequate sleep could treat or prevent obesity by taking gender differences into consideration.