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.