Predisposing factors of daytime sleepiness in obese OSA patients

Excessive daytime sleepiness is a common symptom in obese patients with obstructive sleep apnea. We investigated predisposing factors of excessive daytime sleepiness by comparing obese non-sleepy with sleepy patients with obstructive sleep apnea. Excessive daytime sleepiness was determined by the Epworth Sleepiness Scale in 43 patients (34 men and 9 women) with obstructive sleep apnea (apnea-hypopnea index ≥ 15 events per hr) and obesity (body mass index ≥ 30 kg m^-2 ). Two subgroups were formed with (Epworth Sleepiness Scale ≥ 11) and without (Epworth Sleepiness Scale < 11) excessive daytime sleepiness. The concept of excessive daytime sleepiness was compared with other established daytime performance tests (Stanford Sleepiness Scale, Multiple Sleep Latency Test, Pupillographic Sleepiness Test, Marburger Vigilance test). Associations were calculated between excessive daytime sleepiness and demographic, metabolic and polysomnographic data. We included 19 sleepy patients (mean Epworth Sleepiness Scale score 15.2) and 24 non-sleepy patients (mean Epworth Sleepiness Scale score 5.8). Epworth Sleepiness Scale was negatively correlated with age and morning cortisol. Epworth Sleepiness Scale was positively correlated with body mass index, Stanford Sleepiness Scale, Beck's Depression Inventory and Marburger Vigilance test. Sleepy obese patients were significantly younger (mean 49.1 years), showed lower morning cortisol level (mean 9.41 μg L^-1 ) and a trend to higher body mass index (mean 37.5 kg m^- ²) compared with non-sleepy obese patients (mean: 59.3 years, 5.7 μg L^-1 , 34.6 kg m^- ², respectively). Many different excessive daytime sleepiness phenotypes are probably enclosed in obese patients with obstructive sleep apnea. Epworth Sleepiness Scale scores were best reflected by the objective Marburger Vigilance test results. The objective test can be particularly useful in cohorts where subjective reports are unreliable and operational readiness is paramount. Sleepy and non-sleepy obese patients with obstructive sleep apnea were similar in all polysomnographic parameters. Sleepy patients were younger, heavier and showed lower morning cortisol levels than non-sleepy patients.