The association between residual excessive sleepiness and polysomnography parameters in patients with obstructive sleep apnea using oral appliances

Objective Oral appliances (OA) are effective in reducing apnea-hypopnea index (AHI) in patients with obstructive sleep apnea (OSA). However, residual excessive sleepiness (RES) may occur despite successful OA treatment, and there is limited evidence on the cause of this. Furthermore, few studies have examined the association between changes in sleepiness after OA treatment and polysomnography (PSG) parameters. The purpose of this study was to evaluate the prevalence of RES after OA treatment and examine the effects of changes in sleepiness on PSG parameters. Methods The study sample included 121 participants who were diagnosed with OSA and had evaluated RES after OA treatment outcomes using PSG. All patients were scored using the Epworth sleepiness scale (ESS) at baseline and after OA treatment, and the association between changes in ESS and PSG parameters were examined statistically. Results Approximately 20.5% of OA responders (n = 73) exhibited RES. The ESS change better group (n = 24, ESS decreased by ≥2 points after treatment) exhibited significantly lower baseline lowest SpO2 values (82.0 ± 7.9 vs. 87.5 ± 4.2; p-value <0.01) and higher baseline CT90 value (2.4 ± 4.0 vs. 0.5 ± 0.9; p-value <.05) compared to the ESS change worse group (n = 19, ESS increased by ≥2 points after treatment). Moreover, the CT90 change rate after OA treatment was also significantly higher in the former group. Conclusion OSA patients can exhibit RES despite improvements in AHI after OA treatment. Furthermore, improvements in ESS can potentially help predict hypoxia parameters in PSG.