Global prevalence of metabolic syndrome in adults with obstructive sleep apnoea: A systematic review and meta-analysis

Metabolic syndrome (MetS) is considered to exhibit increased prevalence among adults with obstructive sleep apnoea (OSA), but the reported prevalence estimates among such patients vary. Thus, this systematic review and meta-analysis aimed to investigate the global prevalence of MetS in adults with confirmed OSA. Ovid Medline, Embase, CINAHL, and the Cochrane Library databases were searched for all primary studies published in English that used standard polysomnography for OSA diagnosis and reported MetS estimates. At least two reviewers independently screened for eligible studies, extracted data, and graded the risk of bias using the Risk of Bias Assessment Tool for Non-randomised Studies (RoBANS). Three-level random-effects model was applied for the meta-analysis, reporting pooled prevalence estimate with 95% confidence intervals (CIs). Pre-specified subgroup analyses and meta-regression were also performed. Heterogeneity was quantified using I2 and chi-square statistics. A total of 102 studies were eligible for inclusion (34,013 adults with OSA from 28 countries). The combined MetS prevalence was 55.4% (95% CI: 51.0%, 59.8%). Considerable heterogeneity was noted among the included studies (I2 = 97.8%), whilst the risk of bias ranged from low to high. Subgroup analysis examining the effects of geographic region, study design, MetS definition, and apnoea-hypopnea index threshold showed a significant variation in prevalence estimates across most subgroups (p < 0.0001). Meta-regression analysis indicated a positive association between mean body mass index (β = 0.0772, t = 4.56, p < 0.0001) and MetS prevalence. MetS has a high prevalence among adults with polysomnography-confirmed OSA, underscoring the need for prompt MetS screening in these patients. Future longitudinal and genetic/mechanistic studies should investigate the factors accounting for this association.