The interaction between hypertension and obstructive sleep apnea on subjective daytime sleepiness

Hypertension is one of the most common chronic cardiovascular diseases in adults while obstructive sleep apnea (OSA) is the most common type of sleep apnea. It was recently reported that the mean Epworth Sleepiness Scale (ESS) score, measuring subjective daytime sleepiness, was significantly higher in non-hypertensive subjects than the hypertensive counterparts with moderate to severe obstructive sleep apnea. In the current study, the authors investigated the interaction between hypertension and OSA on daytime sleepiness among 280 subjects recruited from a sleep study. OSA was evaluated with the Apnea-Hypopnea Index (AHI), and daytime sleepiness was measured with the ESS. Significantly higher mean ESS scores were found for subjects without than those with hypertension (11.3 vs 9.4, P = 0.003) but only a marginally significant difference was discerned for the ESS scores between subjects with AHI >= 15/h and AHI <15/h (P = 0.075). A significant interaction between hypertension and OSA status on daytime sleepiness was observed from the analysis of variance (P = 0.02). The adjusted mean ESS score for the group of normotensive subjects with moderate to severe OSA (13.11) was significantly higher than the other three groups, namely, normotensive subjects with mild OSA (9.35), hypertensive subjects with mild OSA (9.70), and hypertensive subjects with moderate to severe OSA to (9.43). In conclusion, subjective daytime sleepiness of normotensive subjects with moderate to severe OSA was significantly more severe than other subjects.