Purpose: Inadequate sleep has negative metabolic consequences that may contribute to obesity. A priori hypotheses posit relationships between sleep characteristics, carbohydrate and lipid metabolism, appetite, fatigue, and obesity in laboratory, clinical, and population settings. There are few reports from primary care; and none that address sleep duration, quality, and stability. This study examines the relationship between three sleep characteristics-duration, quality, or stability-and obesity in our urban hospital affiliated family medicine center in Akron, Ohio.
Methods: A systematic sampling process yielded 225 representative patients who completed the Pittsburgh Sleep Quality Index, the Berlin Apnea Questionnaire, and the Sleep Timing Questionnaire. Demographic, body mass, hypertension, and insurance data were obtained from the electronic medical record. Associations between self-reported sleep characteristics and obesity were examined via contingency tables and regression models.
Results: Seventy-eight percent (78%) reported poor quality sleep, 59% had elevated Berlin apnea-risk scores, 12% reported restless legs symptoms, and 9% reported a prior diagnosis of sleep apnea; 62% were obese. We found significant (p < 0.05) associations between sleep quality, duration or bedtime stability, and obesity. The association between sleep quality and obesity was negative and linear (69%, 72%, 56%, 43%), while the association between sleep duration and obesity was U-shaped (74%, 53%, 53%, 62%; linear term p = 0.02 and quadratic term p = 0.03). Less stable bedtimes during the week (OR = 2.3, p = 0.008) or on the weekend (OR = 1.8, p = 0.04) were also associated with obesity. The association between sleep quality and obesity was not explained by patient demographics or snoring (ORadj = 2.2; p = 0.008).
Conclusion: This study adds to the sparse literature on the relationship between three self-reported sleep characteristics and obesity in urban primary care settings which typically differ from both general population and specialty outpatient settings.
Keywords: Sleep quality; obesity; primary care; sleep duration; sleep timing.