Digest author(s): Matteo Bradicich | 19 December, 2023
Obstructive sleep apnoea (OSA) is defined by recurrent upper airway occlusions leading to overnight intermittent hypoxia and sleep fragmentation, which are considered the major pathophysiological drivers of increased cardiovascular risk among OSA patients. Among other beneficial effects, continuous positive airway pressure (CPAP) improves blood pressure values and reduces cardiovascular risk in a primary prevention setting. The individual participant data (IPD) meta-analysis by Sánchez-de-la-Torre et al. aims to assess the impact of CPAP therapy on secondary cardiovascular risk prevention.
After having carried out a literature research in the major online paper repositories, two authors screened the retrieved papers for inclusion and independently extracted the relevant information from them. The analysis included randomised controlled trials (RCT) on adult patients with moderate to severe OSA, diagnosed with a polysomnography or a home sleep apnoea test, and known cardiac or cerebrovascular disease, assessing the prevention potential of an intervention exclusively with CPAP used for at least 6 months, compared against no CPAP therapy. The primary outcome of the analysis was a composite of the first major adverse cardiac or cerebrovascular event (MACCE) or death from cardiovascular causes, myocardial infarction, stroke, revascularisation procedure, hospital admission for heart failure, hospital admission for unstable angina, or hospital admission for transient ischemic attack. Secondary cardiovascular end points included the individual components of the primary composite end point.
Three RCTs were included in the final IPD analysis, summarising data of 2097 patients (50.1%) randomised to CPAP and 2089 (49.9%) randomised to no CPAP. The mean follow-up time was 39 months. The risk of bias of the included studies was deemed as low in all domains. A total of 691 MACCEs were observed (349 in the CPAP group and 342 in the no CPAP group), with no significant differences in their incidence between the two groups. After a decrease in the first 12 months of observation, CPAP adherence remained stable over time, with an overall adherence of 3.03 hours per night. Although no significant reduction in the incidence of MACCEs was observed on CPAP therapy, an analysis with a marginal structural Cox model accounting for time-varying and baseline confounding factors showed a decreased cardiovascular event risk associated with good CPAP adherence (HR, 0.69 [95% CI, 0.52-0.92]; p =0.01).
This IPD meta-analysis revealed that adequate adherence to CPAP (≥4 hours of CPAP usage per night) is associated with a reduction in the risk of cardiovascular events recurrence in a secondary prevention setting, therefore underlining the paramount importance of CPAP therapy among this specific OSA patient subgroup, which intrinsically represents a population at higher risk due to the pathophysiology underlying this sleep breathing disorder and the positive history for cardiovascular events. The improvement in cardiovascular risk is presumably associated with the CPAP-mediated reduction of nocturnal hypoxemia, autonomic imbalance, and endothelial dysfunction. Considering the medical and socio-economic impact of secondary prevention in this OSA population, the identification of factors influencing CPAP adherence, such as an initial positive experience with it, will be of crucial relevance in the upcoming research.