Increased erythrocyte adhesiveness and aggregation in obstructive sleep apnea syndrome

Obstructive sleep apnea (OSA) is associated with an increased incidence of stroke and myocardial infarction as well as increased prothrombotic and inflammatory processes. Although erythrocyte adhesiveness/aggregation is known to be elevated in cardiovascular diseases, it has never been evaluated in OSA. The aim of this study was to examine the possible association of OSA and erythrocyte adhesiveness/aggregation.

The study was conducted in the Sleep Laboratory of a tertiary university-affiliated medical center in 79 patients (age 57.1+/-12.9 years) with a diagnosis of OSA (apnea hypopnea index 41.2+/-25.9). Findings were compared with data on 1079 controls without clinical symptoms of OSA, matched for sex, age, and body mass index. Overnight polysomnography and blood sampling for erythrocyte sedimentation rate, levels of fibrinogen, high-sensitivity C-reactive protein, and erythrocyte adhesion/aggregation test consisting of measures of erythrocyte percentage and vacuum range on image analysis.

The study group had significantly higher values than controls of all three markers of inflammation (p<0.001 for erythrocyte sedimentation rate and fibrinogen; p=0.037 for C-reactive protein). Erythrocyte percentage was significantly lower in the sleep apnea group (84.05+/-15.97 vs. 90.79+/-11.23%, p<0.001), and vacuum range was significantly higher (8.22+/-7.98 vs. 4.63+/-4.05 microm, p<0.001), indicating stronger erythrocyte adhesion/aggregation. Both these factors were significantly correlated with erythrocyte sedimentation rate and to hs-CRP (percentage: r=-0.630; 0.258, p=0.005; 0.031; vacuum range: r=0.494; -0.328, p=0.001; 0.005 respectively).

OSA is associated with increased erythrocyte aggregation/adhesion, which is correlated with an increase in inflammation markers. These findings might help explain the increased cardiovascular morbidity in OSA.