Relationship between obstructive sleep apnea and diurnal leptin rhythms

Study Objectives: Several studies have reported an association between obstructive sleep apnea and leptin, a hormone that influences satiety and body weight. We evaluated the relationship of leptin levels and the overnight change in levels with sleep apnea. Design: Cross-sectional analysis of data from a prospective cohort study. Setting: Case Western Reserve University General Clinical Research Center. Patients or Participants: A total of 138 individuals participating in the Cleveland Family Study -59% women, 45% African -American, with mean apnea-hypopnea index (AHI) of 6.9 (range 0-106)-were studied. Interventions: None. Measurements and Results: Serum leptin was measured at 10:00 pm to 11:00 pm and at 7:00 am to 8:00 am. Leptin levels in both the morning and evening were positively correlated with apnea-hypopnea index (AHI) in age-, sex-, and race-adjusted analyses (P <.0001) but not after additional adjustment for body mass index. The evening/morning leptin ratio, however, was associated with AHI independent of age, sex, race, body mass index, and waist-hip ratio (P =.03). Conversely, AHI was an independent predictor of the leptin ratio (P =.001) and more predictive than arousal index, oxygenation indices, time asleep, or sleep-stage distribution. An AHI > 15 was associated with a 23% increase in leptin ratio. Conclusions: These findings suggest that sleep apnea may suppress secretion of leptin in the morning. Alternatively, the relative elevation in evening leptin may influence apnea pathogenesis.