Is excessive daytime sleepiness a predictor of carotid atherosclerosis in sleep apnea?

Objective: To elucidate the relationship between excessive daytime sleepiness (EDS) in obstructive sleep apnea (OSA) and carotid atherosclerosis determined by ultrasonography and serum surrogate markers.
Methods: One hundred and forty-seven patients (102 males) with snoring and sleep-disordered breathing were investigated. Carotid atherosclerosis was evaluated by serum analysis of high-sensitivity C-reactive protein and fibrinogen and four sonographic indices: intima media thickness (IMT) of the common carotid artery (CCA), IMT from the bulb to the internal carotid artery (ICA), combined IMT measurements from all segments and a plaque score. EDS was assessed by the Epworth Sleepiness Scale (ESS). Pearson correlation analysis, intergroup comparison (ANOVA) and two multiple regression models explored associations between confounders, surrogate markers and EDS.
Results: Forty-four patients had no OSA (apnea-hypopnea index AHI<5h(-1)), 27 mild (5-15), 25 moderate (15-30) and 51 severe OSA (>30). The ESS significantly distinguished severe OSA from non-OSA patients (p=0.003). It showed significant correlations with the BMI, HbA1c, systolic RR, the AHI, sleep time spent with an oxygen saturation <90%, the respiratory arousal index, IMT of the CCA and combined IMT measurements, but no correlation with serum markers. The ESS was found to be an independent predictor of CCA-IMT in the pre-polysomnographic multiple regression model (p=0.008), but not in the post-polysomnographic model after including respiratory variables.
Conclusion: EDS is associated with obesity, diabetes and all respiratory variables in OSA patients and may serve as an independent predictor of carotid atherosclerosis before polysomnography.