Predictors of daytime sleepiness in patients with obstructive sleep apnea

The main symptomatic criterion to diagnose obstructive sleep apnea (OSA) is the level of daytime sleepiness. The Epworth Sleepiness Scale is a simple, self-administered questionnaire which provides a measurement of the subject's general level of daytime sleepiness. The aim of this study was to investigate the factors that can predict daytime sleepiness in patients with sleep apnea.

50 consecutive patients with obstructive sleep apnea were enrolled into the study. Age, gender, anthropometric and polygraphic data were thoroughly analyzed. In all subjects daily sleepiness was assessed by Epworth Sleepiness Scale.

The mean age of the subjects was 54.7 ± 12.8 years, 82% males. The mean BMI was 31.9 ± 6 kg/m2. Pearson correlation coefficient analysis demonstrates a significant positive correlation between the Epworth Sleepiness Scale and the desaturation index (r = 0.31, p < 0.01) and arterial hypertension (r = 0.32, p < 0.01). The forward stepwise regression analysis shows that the apnea hypopnea index and desaturation index are important predictors of daytime sleepiness in patients with obstructive sleep apnea which explains 40% of the Epworth Sleepiness Scale score.

The desaturation index showed the strongest correlation with the Epworth scale. According to the results of the backward stepwise multiple regression and logistic regression, the predictors for the level of daytime sleepiness are oAHI and index of desaturation. According to the analysis of the ROC curve, desaturation index is a predictor of a high specificity.