The Sociodemographic and Risk Factors for Keratoconus: Nationwide Matched Case-Control Study in Taiwan, 1998-2015

The aim of this study was to determine the sociodemographic and risk factors for keratoconus (KC) patients with a nationwide Asian database. Population-based matched case-control study. We performed a secondary data analysis of the Taiwan National Health Insurance Research Database (NHIRD). Cases were patients with newly diagnosed KC in 1998-2015. Controls were patients without KC and matched 4:1 with the KC cases by age, sex, and index date. Comorbidities diagnosed before KC included diabetes mellitus (DM), asthma, allergic rhinitis, mitral valve prolapse, collagen vascular disease, aortic aneurysm, Down syndrome, sleep apnea, depression, hyperlipidemia, astigmatism, and myopia. Conditional logistic regression with forward selection were used to obtain risk factors for KC. A total of 5,055 patients with KC were matched with 20,220 controls. The average age at KC first diagnosis was 29.76 years. Individuals who lived in suburban and rural area had lower odds ratio of KC (adjusted odds ratio [OR] 0.86, 95% confidence interval [CI] 0.80-0.94; and 0.73, 95% CI 0.67-0.79; respectively) when comparing with those who lived in urban area. Multivariate analysis revealed that Down syndrome, astigmatism, myopia, allergic rhinitis, and asthma were positively associated with KC with adjusted odds ratios (adjusted OR 8.69, 95% CI 3.74-20.19; 6.23, 95% CI 5.35-7.24; 2.99, 95% CI 2.70-3.32; 1.22, 95% CI 1.14-1.32; and 1.18, 95% CI 1.07-1.30, respectively). On the other hand, hyperlipidemia, depression, and DM (uncomplicated and complicated) were negatively associated with KC (adjusted OR 0.67, 95% CI 0.59-0.77; 0.58, 95% CI 0.48-0.71; 0.77, 95% CI 0.64-0.93; and 0.61, 95% CI 0.44-0.86, respectively). Our study found that patients with hyperlipidemia, depression, or DM were less likely to have KC, and patients with asthma, allergic rhinitis, astigmatism, myopia, or Down syndrome had higher odds ratio of KC.