Treatment with continuous positive airway pressure and diurnal and nocturnal serum melatonin concentration in patients with obstructive sleep apnea.

INTRODUCTION    Melatonin secretion, one of the main factors controlling the sleep-wake rhythm, may be disrupted in subjects with sleep disorders. OBJECTIVES    To evaluate the profile of circadian melatonin secretion in patients with obstructive sleep apnea (OSA) and to assess the impact of a 2 day and a 3-month period of treatment with continuous airway pressure (CPAP) on diurnal and nocturnal serum melatonin. PATIENTS AND METHODS    Serum melatonin was evaluated in 71 untreated OSA patients and 18 healthy controls at six time points: 10 am, 2 pm, 6 pm, 10 pm, 2 am, 6 am. The measurements were repeated after 2 days and 3 months of CPAP treatment. RESULTS    Melatonin secretion rhythm was altered in 25.4% patients with OSA. In patients with preserved secretion rhythm, serum melatonin was significantly lower at 2 am. and 6 am. when compared to healthy controls: 68.2 (30.1-109.8) pg/ml vs 109.1 (63-167.9) pg/ml, P = 0.02 and 40.8 (20.8-73.2) pg/ml vs 67.7 (32.7-131.7) pg/ml, P = 0.04, respectively. Melatonin levels did not change significantly after the 2-day and the 3-month period of CPAP treatment. However, after 3 months of CPAP use, a shift of peak melatonin concentration to 2 am. was observed in patients with an altered secretion rhythm. CONCLUSIONS    OSA has a significant impact on serum melatonin. Neither short-term nor long-term CPAP treatment significantly changes melatonin concentrations, however, our results seem to indicate that a 3-month period of CPAP treatment may be helpful in restoring the physiologic rhythm of melatonin in OSA patients with a disrupted secretion profile.