Abstract
BACKGROUND: Obstructive sleep apnea (OSA) and chronic rhinosinusitis (CRS) are common conditions that impair quality of life and are linked to adverse health outcomes. Evidence on their bidirectional association remains inconsistent. This study aimed to investigate the OSA-CRS relationship through systematic review, meta-analysis, and Mendelian Randomization (MR). METHODS: We systematically reviewed 14 observational studies (30,509 participants) following PRISMA and MOOSE guidelines. Meta-analyses were performed in Stata 15.0 and Review Manager 5.4 to estimate pooled prevalence and risk ratios. Bidirectional two-sample MR used GWAS summary data, analyzed in R (v4.2.0) with the TwoSampleMR package; IVW was the primary method, complemented by MR-Egger and leave-one-out analyses to assess pleiotropy and robustness. RESULTS: Observational studies indicate a bidirectional association between CRS and OSA, with CRS patients showing an increased risk of OSA, and OSA patients having a higher risk of developing CRS. Mendelian Randomization analysis, however, supports a unidirectional causal relationship, showing that CRS causally increases the risk of OSA, whereas there is no significant causal effect of OSA on CRS. Specifically, the meta-analysis revealed a 20% prevalence of OSA among CRS patients (95% CI: 19-21%) and an elevated risk of OSA in this group (OR = 1.14, 95% CI: 1.08-1.20). Patients with OSA exhibited a 5.8-fold higher risk of developing CRS (OR = 5.79, 95% CI: 1.61-20.80). Mendelian Randomization analysis confirmed the causal effect of CRS on OSA (IVW OR = 1.11, 95% CI: 1.03-1.20, p = 0.008), while the reverse direction showed no significant association (OR = 1.0, 95% CI: 0.9-1.1). CONCLUSION: Research data indicate bidirectional associations between OSA and CRS, but MR supports only a causal effect of CRS on OSA. These findings identify CRS as a modifiable risk factor for OSA, supporting targeted OSA screening in CRS populations. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s41105-026-00641-z.