A systematic review, meta-analysis and regression of the effect of CPAP on metabolic and inflammatory markers in obstructive sleep apnea

The effect of continuous positive airway pressure (CPAP) on reducing inflammatory and metabolic markers plays an important role in obstructive sleep apnea (OSA) management, however data remains inconsistent. This systematic review and pre-post meta-regression indicate the effect of CPAP on improving inflammation and metabolic markers in patients with OSA. A systematic search was performed on PubMed, Web of Science and Scopus, including English, full-access trials with CPAP-naïve adult patients with OSA. Markers of choice were CRP, IL-6, TNF-alpha, LDL, insulin, insulin resistance, leptin, adiponectin and homocysteine. Data about confounders were collected and used in a meta-regression to assess their relationship with the intervention. Studies underwent a sensitivity analysis and the certainty of evidence was evaluated using GRADE frameworks. CPAP therapy significantly reduces CRP (-0.48 SMD [-0.65, -0.31]) and LDL (-0.32 SMD [-0.43, -0.20]) levels. The effect on reducing insulin resistance remains fragile and lacked robustness in sensitivity analysis. Evidence certainty proved low across these outcomes due to heterogeneity, indirectness and publication bias. CPAP improved IL-6 levels (-0.31 SMD [-0.54, -0.08]). After the sensitivity analysis, post-therapeutic leptin levels showed to be slightly improved (-0.19 SMD [-0.32,-0.05]). Meta-regression results indicated that daily CPAP hours usage was associated with better CRP reduction (β = −0.117 per hour/night). No other confounder showed a significant association. CPAP improves inflammatory and metabolic status, lowering inflammatory markers, LDL and insulin resistance, although the certainty of evidence was low.