Obstructive Sleep Apnea and Keratoconus: A Systematic Review and Meta-analysis

BACKGROUND Despite the increasing number of studies focused on the association between obstructive sleep apnea (OSA) and keratoconus (KC), to date, no comprehensive meta-analysis or systematic review was published. OBJECTIVE The objective of this study was to evaluate the association between OSA and KC. DATA SOURCES Sources of data were PubMed, Scopus, and Web of Science databases. STUDY ELIGIBILITY CRITERIA The criteria for study eligibility were case-control studies and cohort studies reporting data on the association of OSA with KC with risk ratio, odds ratio, or hazard ratio with 95% confidence intervals or sufficient raw data for calculation. STUDY APPRAISAL AND SYNTHESIS METHODS Meta-analysis was conducted with a random-effects model using odds ratio with 95% confidence interval as the effect size. Heterogeneity was evaluated using the Q and I-2 tests. Sensitivity analysis and assessment of publication bias were performed. RESULTS Five studies (four case-control studies and one cohort study) published between 2012 and 2016 and involving 33,844 subjects (16,922 patients with KC, 16,922 controls) were included in this meta-analysis. A significant association between OSA and KC has been shown (pooled odds ratio, 1.841; 95% confidence interval, 1.163 to 2.914; P = .009). A significant heterogeneity was observed (Q = 15.8, I-2 = 74.6%). There was no evidence of significant publication bias (P = .07). The sensitivity analyses indicated the stability of results. LIMITATIONS Heterogeneity across the studies was observed. Data from four hospital-based case-control studies and one large population-based cohort study were combined. Most of the included studies ascertained OSA by the Berlin Questionnaire, which is a screening tool. CONCLUSIONS This meta-analysis provides significant evidence that OSA is associated with KC. Therefore, a proper screening for OSA is warned for KC patients for the prevention of various cardiovascular comorbidities. Further prospective studies are warranted to explore more in-depth the casual relationship between the two conditions.