Efficacy of CPAP duration and adherence for cognitive improvement in patients with obstructive sleep apnea: a meta-analysis of randomized controlled trials

Purpose Obstructive sleep apnea (OSA) can impair cognition. Continuous positive airway pressure (CPAP) is a recommended treatment for OSA but its effectiveness on cognitive improvement is uncertain, a finding which may be biased by various durations and adherence to treatment with CPAP. In a meta-analysis assessing high-quality randomized controlled trials (RCTs), we estimated whether or not CPAP benefits cognition in patients with OSA. Methods PRISMA criteria were followed in the performance of this meta-analysis. The weighted mean difference (WMD) and 95% confidence interval (CI) of six neuropsychological scores covering eight cognitive domains were used to evaluate the benefit between CPAP and non-CPAP interventions. Subgroups of different therapeutic durations and adherence, which were divided into short-term (< 8 weeks) and long-term (≥ 12 weeks) durations, and poor (nighttime < 4 h/night) and good (nighttime ≥ 4 h/night) adherence were also analyzed. Results Among 16 RCTs, 1529 participants with OSA were included. Comparing the CPAP group and the control group for all treatment durations and adherence, a mild improvement for digit span forward which reflected short-term memory was observed (WMD[95%CI] = 0.67[0.03,1.31], p = 0.04). Trail making test-part B, which reflected executive function was improved for participants with OSA who had good adherence to CPAP (WMD[95%CI] = − 6.24[− 12.60,0.12], p = 0.05). Patients with OSA who received short-term CPAP treatment (WMD[95%CI] = − 7.20[− 12.57, − 1.82], p = 0.009) had a significant improvement in executive function when compared with controls. There was no statistical difference for all scales between long-term (≥ 12 weeks) CPAP treatment group and control group. Conclusion The effectiveness of CPAP on cognitive improvement in patients with OSA is limited, although good adherence to CPAP can mildly benefit executive function with short-term effectiveness.