Introduction: Obstructive sleep apnea syndrome (OSAS) is considered to be associated with cardiovascular complications, and atherosclerosis could mediate this relationship. Cardiovascular risk factors of OSAS still need to be elucidated in elderly patients, since studies about the association between OSAS and cardiovascular diseases have been done mainly in middle-aged adults. To investigate whether endothelial dysfunction, as an early marker of atherosclerosis, and inflammatory responses in OSAS were affected by age, we studied flow-mediated dilatation (FMD) and C-reactive protein (CRP) in elderly and middle-aged patients with OSAS.
Materials and methods: This study enrolled 161 male subjects of 117 middle-aged (35-59 years old) and 44 elderly (>or=60 years old) patients with OSAS. After they finished nocturnal polysomnography (NPSG), FMD was measured on the brachial artery and blood samples were obtained to determine serum CRP levels.
Results and discussion: FMD was significantly lower in the elderly patients (p = 0.04), but no difference was observed between two age groups in body mass index (BMI), neck circumference, waist-to-hip ratio, apnea hypopnea index (AHI), serum CRP level, or NPSG findings related with nocturnal hypoxemia such as average O(2) saturation, percentage of time below 90% O(2) saturation, and oxygen desaturation index (ODI). From the results of stepwise multiple linear regression analysis, the lowest oxygen saturation was a significant determinant of FMD (beta = 0.25, p < 0.01, adjusted R (2) = 6%), and BMI (beta = 0.22, p < 0.05) and waist-to-hip ratio (beta = 0.21, p < 0.05) were significant variables to explain CRP (adjusted R (2) = 11%, p < 0.01) in the middle aged patients. In the elderly patients, no variable was significant for predicting FMD, but AHI was significant determinant of CRP (beta = 0.46, p < 0.01, adjusted R (2) = 19%, p < 0.01). In predicting cardiovascular risks of OSAS, both hypoxia and obesity should be considered in the middle-aged group, whereas nocturnal respiratory disturbances are important in the elderly group.