The relationship between the Epworth Sleepiness Scale, the Functional Outcomes of Sleep Questionnaire, and respiratory sleep parameters in obstructive sleep apnea before and after oral appliance therapy: a prospective study

This prospective single-center study evaluates the relationship between self-reported symptoms, the Epworth Sleepiness Scale (ESS), the Functional Outcomes of Sleep Questionnaire-30 (FOSQ-30), and respiratory parameters in diagnostic sleep studies of patients with moderate obstructive sleep apnea, before and after oral appliance therapy. Seventy-six patients were included and completed the ESS and FOSQ-30 and reported anamnestic complaints. Subsequently, a sleep study was conducted. All patients were treated with oral appliance therapy. After six months, follow-up assessments including questionnaires and a sleep study were performed. Fifty-six patients successfully completed the study. A negative significant relation between pre-treatment ESS and pre-treatment apnea-hypopnea index and a significant relation between Δ FOSQ-30 and Δ apnea-hypopnea index and Δ oxygen desaturation index was found. No other significant relationships between the respiratory sleep parameters and ESS or FOSQ-30 were found at other time points. This was consistent across all ESS levels, with no stronger correlation at increased sleepiness. The reported symptoms were comparable between the responders and non-responders. Reported sleepiness was related to higher ESS and lower FOSQ-30 scores. In conclusion, this study reveals no clinically relevant relationship between the ESS and FOSQ-30 and the respiratory sleep parameters before and after oral appliance therapy in patients with moderate obstructive sleep apnea. The change in FOSQ-30 scores due to oral appliance therapy did correlate with the change in the apnea-hypopnea index and the oxygen desaturation index. Symptoms reported during an office appointment correspond adequately with the ESS and FOSQ-30, but not with the respiratory sleep parameters.