Changes in sleep duration and changes in weight in obese patients: The Swedish Obese Subjects Study

Sleep duration has been linked to obesity and/or weight gain in a number of cross-sectional and longitudinal observational studies. The Swedish Obese Subjects Study (SOS) is a non-randomized controlled trial of surgical interventions (surgical group) for weight-loss compared with standard conservative weight loss management (control group). We investigated whether changes in sleep duration were associated with weight loss in severely obese patients. This is a longitudinal treatment study reanalyzed as two 10-year cohorts, surgical (n = 1139) and control (n = 952). Self-reported habitual sleep duration, body weight, total cholesterol, HDL (high density lipoprotein) cholesterol, triglycerides, fasting glucose, and blood pressure were measured at baseline, 2 years, and 10 years. At baseline patients were obese (inclusion: body mass index [BMI] >= 34 for men and >= 38 for women) and middle aged (37-60 years). The surgical group had substantially greater weight reduction after 10 years (-19.1 kg) compared with the control group (+1.2 kg). Changes in sleep duration between baseline, 2 years, and 10 years were not associated with body mass or with changes in weight in either cohort. Changes in cardiovascular disease (CVD) risk factors were not associated with changes in sleep duration. Changes in sleep duration over 2 and 10 years were not associated with weight loss in these obese patients. The data from the SOS study offers no support to the hypothesis that sleep-duration modification is associated with obesity reduction in severely obese people.