Background: The prevalence of chronic sleep deprivation is increasing in modern societies with negative health consequences. Recently, an association between short sleep and obesity has been reported.
Primary objectives: To assess the feasibility of increasing sleep duration to a healthy length (approximately 7(1/2) h) and to determine the effect of sleep extension on body weight.
Secondary objectives: To examine the long-term effects of sleep extension on endocrine (leptin and ghrelin) and immune (cytokines) parameters, the prevalence of metabolic syndrome, body composition, psychomotor vigilance, mood, and quality of life.
Methods: One hundred-fifty obese participants who usually sleep less than 6(1/2) h, are being randomized at a 2:1 ratio to either an Intervention or to a Comparison Group. They are stratified by age (above and below 35) and the presence or absence of metabolic syndrome. During the first 12 months (Efficacy Phase) of the study, participants are evaluated at bi-monthly intervals: the Intervention Group is coached to increase sleep by at least 30-60 min/night, while the Comparison Group maintains baseline sleep duration. In the second (Effectiveness) phase, participants converge into the same group and are asked to increase (Comparison Group) or maintain (Intervention Group) sleep duration and are evaluated at 6-month intervals for an additional 3 years. Non-pharmacological and behavior-based interventions are being utilized to increase sleep duration. Endocrine, metabolic, and psychological effects are monitored. The sleep, energy expenditure, and caloric intake are assessed by activity monitors and food recall questionnaires. At yearly intervals, body composition, abdominal fat, and basal metabolic rate are measured by dual energy X-ray absorptiometry (DXA), computerized tomography (CT), and indirect calorimetry, respectively.
Results: As of January 2010, 109 participants had been randomized, 64 to the Intervention Group and 45 to the Comparison Group (76% women, 62% minorities, average age: 40.8 years; BMI: 38.5 kg/m(2)). Average sleep duration at screening was less than 6 h/night, 40.3 h/week. A total of 28 Intervention and 22 Comparison participants had completed the Efficacy Phase.
Limitations: The study is not blinded and the sample size is relatively small.
Conclusions: This proof-of-concept study on a randomized sample will assess whether sleep extension is feasible and whether it influences BMI. Clinical Trials 2010; 7: 274-285. http://ctj.sagepub.com.