Impaired circadian variation of platelet activity in patients with sleep apnea

Cardiovascular diseases are frequent in patients with obstructive sleep apnea (OSAS). There is evidence that the day-night pattern of myocardial infarction and sudden cardiac death observed in the general population is altered in patients with OSAS. This study investigates potential abnormalities in the circadian profiles of platelet activity in OSAS. We studied 37 patients with OSAS [7 of whom were also studied after 3 months on continuous positive airway pressure (CPAP) treatment] and 11 controls. In each subject, we obtained six different blood samples during 24-h period (2200, 0200, 0600, 1000, 1400, and 1800 hours). Platelet activity was determined by flow cytometry immediately after sampling. We found that nocturnal platelet activity was significantly increased in patients with OSAS (p = 0.043) and that effective treatment with CPAP decreased platelet activity in these patients but differences just failed to reach statistical significance (p = 0.063). OSAS is associated with increased platelet activity during the night, and that this appears to be improved by chronic use of CPAP. These results may contribute to explain the high prevalence of cardiovascular events during sleep in OSAS.