Diurnal and nocturnal serum melatonin concentrations after treatment with continuous positive airway pressure in patients with obstructive sleep apnea.

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