Background CPAP reduces blood pressure (BP) in patients with symptomatic obstructive sleep apnoea (OSA). Whether the same benefit is present in patients with minimally symptomatic OSA is unclear, thus a meta-analysis of existing trial data is required.

Methods The electronic databases Medline, Embase and trial registries were searched. Trials were eligible if they included patients with minimally symptomatic OSA, had randomised them to receive CPAP or either sham-CPAP or no CPAP, and recorded BP at baseline and follow-up. Individual participant data were obtained. Primary outcomes were absolute change in systolic and diastolic BP.

Findings Five eligible trials were found (1219 patients) from which data from four studies (1206 patients) were obtained. Mean (SD) baseline systolic and diastolic BP across all four studies was 131.2 (15.8) mm Hg and 80.9 (10.4) mm Hg, respectively. There was a slight increase in systolic BP of 1.1 mm Hg (95% CI −0.2 to 2.3, p=0.086) and a slight reduction in diastolic BP of 0.8 mm Hg (95% CI −1.6 to 0.1, p=0.083), although the results were not statistically significant. There was some evidence of an increase in systolic BP in patients using CPAP <4 h/night (1.5 mm Hg, 95% CI −0.0 to 3.1, p=0.052) and reduction in diastolic BP in patients using CPAP >4 h/night (−1.4 mm Hg, 95% CI −2.5 to −0.4, p=0.008). CPAP treatment reduced both subjective sleepiness (p<0.001) and OSA severity (p<0.001).

Interpretation Although CPAP treatment reduces OSA severity and sleepiness, it seems not to have a beneficial effect on BP in patients with minimally symptomatic OSA, except in patients who used CPAP for >4 h/night.