Incidence of Keratoconus and Its Association with Systemic Comorbid Conditions: A Nationwide Cohort Study from South Korea

PURPOSE: To determine the incidence of keratoconus and to determine its possible association with common systemic diseases using a nationwide cohort. METHODS: This retrospective nationwide cohort study included 1,025,340 subjects from the Korean National Health Insurance Service-National Sample Cohort database from 2004 to 2013. Estimates for incidence rates of keratoconus were identified. After 1 : 5 matching using propensity scores, associations between keratoconus and certain systemic comorbidities were determined using multivariate logistic regression analysis. RESULTS: The incidence during the same period was 15.1 cases per 100,000 person-years. Adjusted logistic regression analysis after propensity score matching revealed significant associations between keratoconus and allergic rhinitis (odds ratio (OR): 1.86; 95% confidence interval (CI): 1.63–2.13; p < 0.001), asthma (OR: 1.20; 95% CI: 1.06–1.36; p < 0.001), atopic dermatitis (OR: 1.33; 95% CI: 1.13–1.56; p < 0.001), and diabetes mellitus (DM) (OR: 1.35; 95% CI: 1.15–1.58; p < 0.001). CONCLUSION: Estimates of the incidence of keratoconus may help in the planning of eye-care policies, and the results of this study determined the associations between allergic diseases and keratoconus. Conflicting results regarding the association between keratoconus and DM should be further evaluated.