Study objectives: Over a 2-month period, to evaluate serum levels of C-reactive protein (CRP) in new patients with obstructive sleep apnea syndrome (OSAS), upper airway resistance syndrome (UARS), and absence of important comorbidity, as well as in normal controls.
Design: Cross-sectional analysis.
Setting: Sleep disorders clinic.
Patients: 239 successively monitored subjects: 156 subjects were diagnosed with OSAS, 39 with UARS, and 54 controls.
Measurements and results: Clinical information (neurologic, general medical, and otolaryngology examination), body mass index, neck circumference, hip-waist ratio, Epworth Sleepiness Scale, 3 fatigue scales, Sleep Disorders Questionnaire, serum CRP, and polysomnography were collected. Analysis of variance indicated a significant difference between the groups for diastolic blood pressure, respiratory disturbance index, lowest SaO2, and body mass index. The mean serum CRP level was normal in all 3 groups. Only 15 (14 OSAS and 1 UARS) out of 239 subjects had high serum CRP values. CRP levels were significantly correlated with body mass index, esophageal pressures, hip-waist ratio, neck circumference, and blood pressure. Only body mass index was significantly associated with high CRP values; multiple regression showed: adjusted R2 = 0.115, beta = 0.345, P <.001. When men and women were considered separately, body mass index was again significantly associated with high CRP levels.
Conclusion: Obesity is a risk factor for high serum CRP levels in patients with sleep-disordered breathing, as in the general population.