Abstract
Obstructive sleep apnea syndrome (OSAS) is considered as a risk factor to develop cardiovascular diseases. Circulating cell-derived microparticles (MP) are involved in endothelial dysfunction and atherosclerosis; however, their role is not fully explored in the pathophysiology of OSAS. Eleven patients with untreated, moderate to severe OSAS (Pre-CPAP) and 7 healthy controls underwent overnight polysomnography (apnea-hypopnea index (AHI) 40.4±19.5 vs 2.4±2.2, respectively). Blood samples were collected at 11:00 AM, 5:00 PM and 9:00 PM, and then 1:30 AM and 6:00 AM on the following day. Absolute numbers of platelet-derived (CD41a+) and Annexin V+ MP were measured by flow cytometry. Nine OSA patients were re-studied after 2 months of CPAP treatment (Post-CPAP; AHI 1.9±1.7). Comparisons were made by repeated measures ANOVA, and independent and paired t-test, as appropriate. Untreated OSAS patients exhibited higher levels (at 5:00 PM and 9:00 PM time points) and daily variability than healthy controls both in CD41+ (p<0.05) and Annexin V+ (p<0.01) MP levels. In OSAS patients, interestingly, peak daily MP levels occurred at 5:00 PM. There was significant positive correlation between AHI and the circadian variability both of CD41+ (p<0.01, r=0.70) and Annexin V+ (p<0.05, r=0.60) MP levels. Annexin V+ and CD41a+ MP counts decreased after CPAP treatment at 5:00 PM and 9:00 PM time points (p<0.01 Post-CPAP vs Pre-CPAP). Our data demonstrate that increased MP levels can only be detected at certain time points of the day in OSAS patients. The elevation of MP counts is largely reversible by CPAP treatment. The influence of circadian rythm should be considered to assess MP levels in these patients.
- © 2011 ERS
