• Seockhoon Chung, In-Young Yoon, Yoon-Kyung Shin, Chul Hee Lee, Jeong-Whun Kim, Taeseung Lee, Dong-Ju Choi, and Hee Jeong Ahn.
• Department ofNeuropsychiatry, Seoul National University Bundang Hospital, Seongnam, Korea.
• Sleep. 2007 Aug 1;30(8):997-1001.

Study ObjectivesTo investigate flow-mediated dilatation (FMD) and C-reactive protein (CRP) levels in patients with obstructive sleep apnea syndrome (OSAS) in relation with the severity of respiratory disturbances and hypoxemia.DesignAfter subjects had completed nocturnal polysomnography, FMD was measured in the brachial artery, and blood samples were obtained to determine serum CRP levels.SettingSleep laboratory in Seoul National University Bundang Hospital.PatientsNinety men: 22 normal controls, 28 subjects with mild to moderate OSAS, and 40 with severe OSAS.Measurements And ResultsFMD was found to be correlated with oxygen desaturation index (ODI), percentage of time below 90% O2 saturation, average O2 saturation, lowest O2 saturation, systolic blood pressure, apnea hypopnea index (AHI), and body mass index. In addition, CRP was correlated with body mass index, waist-to-hip ratio, neck circumference, diastolic pressure, average O2 saturation and percentage of time below 90% O2 saturation but not with AHI. Stepwise multiple regression showed that the ODI was a significant determinant of FMD (adjusted R2 = 10%, beta = -0.33, P < 0.01). In addition, body mass index (beta = 0.25, P < 0.05) and waist-to-hip ratio (beta = 0.21, P < 0.05) were found to be significantly correlated with CRP (adjusted R2 = 12%, P < 0.05), independently of other factors. There was no correlation between FMD and CRP.ConclusionAs a marker of nocturnal hypoxemia, ODI rather than AHI might better explain the relationship between OSAS and FMD. Because body mass index and waist-to-hip ratio were identified as risk factors of high serum CRP in OSAS, obesity should be considered when predicting cardiovascular complications in OSAS.

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