Melatonin secretion and excretion in patients with obstructive sleep apnea syndrome

Melatonin (MT) secretion and excretion were investigated in patients with obstructive sleep apnea syndrome (OSAS). Nine men, mean age 55.1 years, mean body mass index 31.2, with a previously confirmed diagnosis of moderate to severe OSAS, were tested on two occasions: immediately before initiation of continuous positive airway pressure (CPAP) treatment and again after at least 4 weeks of continuous nocturnal use of CPAP. Serum MT concentrations were determined every second hour between 2000 and 0800 hours. Urine was collected between 2200 and 0700 hours for determination of urinary MT excretion. Sleep apnea recordings included ear oximetry, respiration and body movements, body position, and breathing sounds. Nine healthy male controls were tested on one occasion. We found that the MT secretion, as reflected by the area under the curve (AUC), among the OSAS patients did not differ from that found in healthy controls (MT AUC 1.68 vs. 1.92 nmol/l x h). Sleep apnea recordings were normalized during CPAP treatment. Moreover, the excessive daytime sleepiness disappeared in all patients. Neither MT secretion (MT AUC 1.68 vs. 1.56 nmol/l x h) nor urinary excretion of MT (0.122 vs. 0.108 nmol/9 h) changed significantly as a result of the CPAP treatment.