How is the Epworth Sleepiness Scale related with subjective sleep quality and polysomnographic features in patients with sleep-disordered breathing?

PURPOSE: To determine the relationship between the Epworth Sleepiness Scale (ESS) and the Subjective Sleep Quality (SSQ) or polysomnographic (PSG) features in patients with sleep-disordered breathing (SDB).

METHODS: This is a retrospective study that included 646 untreated patients with a PSG diagnosis of primary snoring (PS) or obstructive sleep apnea syndrome. Patients with SDB were grouped into four categories according to ESS scores: no diurnal sleepiness (DS) = 0-6; mild DS = 7-12; moderate DS = 13-18, and severe DS = ≥19. Analyses of variance were performed to compare SSQ or PSG features among the four ESS severity categories.

RESULTS: We found a significant increase in subjective sleep time in the group of patients with severe DS. With regard to PSG data, we also identified increases in total sleep time (TST) and rapid eye movement (REM) in the group of patients with severe DS.

CONCLUSION: Unexpectedly, DS severity was related with increases in TST and REM sleep. As has been described in SDB patients, a change in muscular tonus throughout sleep onset (and depth) is a causal factor of SDB features and DS impairment. Therefore, we propose that increases in TST and REM are worsening factors of SDB and consequently, also in DS.