Sleep duration and physical function in people with severe obesity: a prospective cross-sectional study

Background Subjects with severe obesity (BMI > 40 kg/m(2)) have worse physical function and sleep less than lean people (BMI 18.5-25 kg/m(2)). Methods In 554 subjects with severe obesity, we compared physical function in those with normal sleep duration (NSD, 6-9 h/night), short sleep duration (SSD, <= 6 h/night) and long sleep duration (LSD, >= 9 h/night). Results The mean (+/- SD) age and BMI were 43.1 (+/- 11.1) years and 50.9 +/- 8.6 kg/m(2) respectively. One hundred ninety-six (35.4%) were male. More subjects in the NSD group (n = 256) were able to ascend and descend a step 50 times than in the SSD group (n = 247) or the LSD group (n = 51, 75.5% vs 62.8% vs 56.9%, p = 0.002). A similar observation was made for step speed (0.45 +/- 0.11 vs 0.43 +/- 0.10 vs 0.40 +/- 0.11 steps/s respectively, p = 0.001). NSD participants were less likely to have fallen in the preceding year compared to LSD participants (21.1% vs 39.2%, p = 0.007) and also reported less low back pain compared to SSD participants (60.8% vs 75.9%, p = 0.004). Conclusions In conclusion, abnormal sleep duration is associated with reduced physical function in non-elderly severely obese subjects. The effects of sleep hygiene interventions in this cohort warrant further assessment and may be beneficial to their physical function.