Development of CPAP Dose Response for Patients with Obstructive Sleep Apnea: Secondary Analysis

Background: First-line treatment for obstructive sleep apnea (OSA) is continuous positive airway pressure therapy (CPAP). Although CPAP is efficacious, the definition of adequate use (effectiveness) is known to be arbitrary. We aimed to characterize a CPAP dose response for short term outcomes, including sleepiness severity and quality of life. Methods We performed secondary analysis on a prospective, observational cohort study of adult patients (≥18 years old) with newly diagnosed OSA (no CPAP, baseline) and six-months after receiving a CPAP device (follow-up). Objective CPAP use was defined as average minutes of CPAP use per night over all nights during the four-week interval before the end of follow-up. Change in Epworth Sleepiness Scale (ESS) and Symptoms of Nocturnal Obstructions and Related Events (SNORE-25) were primary and secondary outcomes, respectively. Multivariate linear regression was performed, adjusting for demographic factors and severity of OSA at baseline. Results Two hundred forty-two patients (mean age 47 +/- 12, 65% male, AHI 33 +/- 25) were enrolled. Patients used their CPAP devices for an average of 258 +/- 153 minutes per night over all nights (range 0-545 minutes). Mean baseline ESS was 10.0 +/- 4.8 and mean score change was -2.9 +/- 4.0. Mean baseline SNORE-25 was 1.5 +/- 0.8 and mean score change was -0.6 +/- 0.7. There was no association between average CPAP use per night over all nights and change in ESS scores (p=0.18, 95% CI -0.005 – 0.001), after adjusting for confounders. However, for each additional 30 minutes per night of CPAP use, there was a 0.024 improvement in SNORE-25 score, and this was a statistically significant association (p=0.002, 95% CI -0.001- -0.0002). Conclusion This suggests for a minimal clinically important change of 0.2 for SNORE-25, patients would need to use their CPAP an additional 250 minutes (i.e., 4 hours and 10 minutes) per night, on average. This work fits within a larger context aimed to develop a validated definition(s) for adequate CPAP use associated with measures of sleep apnea burden, alter CPAP counseling/troubleshooting, and build evidence-based criteria for considering secondary OSA treatments.