Dose-response relationship between positive airway pressure therapy and excessive daytime sleepiness: the HomePAP study

Study Objectives: The clinical benefits of positive airway pressure (PAP) therapy for obstructive sleep apnea are assumed to require adherent PAP usage, defined by the Centers for Medicare & Medicaid Services as >= 4 hours of use >= 70% of nights. However, this definition is based on early data and does not necessarily capture improvements at subthreshold adherence. We explored dose-response relationships between PAP adherence measures and excessive daytime sleepiness from the HomePAP randomized controlled trial. Methods: Participants aged >= 18 years with an apnea-hypopnea index >= 15 events/h and baseline sleepiness (Epworth Sleepiness Scale [ESS] >= 12) received PAP therapy. Data were collected at baseline, 1-month follow-up, and 3-months follow-up. Regression models and receiver operating characteristic curves evaluated PAP measures as predictors of ESS change and normalization (ESS < 10). Results: In 119 participants (aged 49.4 +/- 12.6 years, 66.4% male, 72.3% White), > 50% were PAP nonadherent per Centers for Medicare & Medicaid Services criteria at 3 months. The percentage of nights with PAP use >= 4 hours predicted ESS change (P = .023), but not when controlling for the apnea-hypopnea index. The percentage of nights with >= 4 hours and average PAP use provided the best discrimination for predicting ESS normalization; each 10% increase in PAP use >= 4 hours increased the odds of ESS normalization by 22% (P = .007); those using PAP >= 4 hours had a nearly 3-fold greater odds of ESS normalization (P = .025). PAP use for at least 4 hours and on 70% of nights provided the best balance between specificity (0.50) and sensitivity (0.73). Conclusions: Although subadherent PAP usage may still confer some benefit for patients with obstructive sleep apnea, adherence to current criteria confers the highest likelihood for ESS change and normalization.