Association between chronic kidney disease and the most common corneal ectasia disease (keratoconus): a nationwide cohort study

BACKGROUND: Both keratoconus (KCN) and chronic kidney disease (CKD) are multifactorial conditions with multiple aetiologies and share several common pathophysiologies. However, the few studies that have described the relationship between KCN and CKD are limited to case reports and small case series. This study aimed to evaluate the association between KCN and CKD. METHODS: The study cohort included 4,609 new-onset keratoconus patients ≥ 12 years identified by the International Classification of Diseases, Ninth Revision, Clinical Modification, code 371.6 and recruited between 2004 and 2011 from the Taiwan National Health Insurance Research Database. The age-, sex-, and comorbidity-matched control group included 27,654 non-KCN patients, selected from the Taiwan Longitudinal Health Insurance Database, 2000. Information for each patient was collected and tracked from the index date until December 2013. The incidence and risk of CKD were compared between the two groups. The adjusted hazard ratios (HRs) for CKD were calculated with Cox proportional hazard regression analysis. Kaplan–Meier analysis was used to calculate the cumulative CKD incidence rate. RESULTS: The incidence rate of CKD was 1.36 times higher in KCN patients than in controls without statistically significant difference (95 % confidence interval [CI] = 0.99–1.86, p = 0.06). In total, 29 male KCN patients and 90 male controls developed CKD during the follow-up period. The incidence rate of CKD was 1.92 times (95 % [CI] = 1.26–2.91; p = 0.002) higher in male KCN patients than in controls. After adjusting for potential confounders, including age, hypertension, hyperlipidaemia, and diabetes mellitus, male KCN patients were 1.75 times (adjusted HR = 1.75, 95 % [CI] = 1.14–2.68, p < 0.05) more likely to develop CKD. CONCLUSIONS: We found that male KCN patients have an increased risk of CKD. Therefore, it is recommended that male KCN patients should be aware of CKD.