Although accumulating evidence has shown that there is a U-shaped association between sleep duration and the risk of metabolic disorders related to obesity, its underlying mechanism is still not fully understood. In this study, we analyzed the association of sleep duration with metabolic, anthropometric, and lifestyle factors in patients with type 2 diabetes. Subjects were 280 patients with type 2 diabetes aged 60±14 years with BMI 25.9±5.1kg/m2, and A1C 9.0±1.8%. Patients with advanced complications were excluded from the study. Diets were evaluated by registered dietitians using software. Body composition was assessed by the multi-frequency bioelectrical impedance method. Habitual physical activity included all of leisure-time, occupational, and household ones. Self-reported nightly sleep duration was 6.4±1.4 h with no gender difference. Sleep duration was inversely correlated with A1C levels, total energy intake, and the intake of three major nutrients. Body fat ratio and skeletal muscle mass, but not body weight or BMI, were correlated positively and negatively, respectively, with sleep duration, even after the adjustment for age. When subjects were divided into three groups based on sleep duration, the intake of fat and carbs was highest in short sleepers (<5.5 h). The percentage of patients who had habitual physical activity was lower in long sleepers (>7 h) than in moderate or short sleepers (25.4%, 31.3%, and 44.0%, respectively). Thus, short sleepers ingested more energy, but %body fat was lower than other groups. This apparent paradox can be explained by the high ratio of habitual physical activity in short sleepers. Long sleep duration is likely a marker of low physical capacity in diabetic subjects. Hence, the U-shaped association may be attributable, at least in part, to excessive eating in short sleepers and a sedentary lifestyle in long sleepers.
H. Nakayama: None. Y. Yamada: None. K. Yamada: None. S. Iwata: None. N. Wada: None. Y. Tajiri: None. M. Nomura: None.