Purpose
Several small-scale studies have reported associations between keratoconus (KCN) and an array of systemic diseases but no large-scale study has fully investigated this topic. The purpose of this study is to determine whether an association exists between common systemic diseases, sociodemographic factors, and KCN among a large, diverse group of insured individuals in the United States.
Design
Retrospective longitudinal cohort study
Participants
16,053 patients with KCN were matched 1:1 to 16,053 persons without KCN.
Methods
Persons with KCN were identified using International Classification of Diseases 9th Revision Clinical Modification (ICD-9-CM) billing codes and matched by age, sex, and overall health to a control group with no record of KCN. A multivariable logistic regression assessed whether sociodemographic factors and certain systemic diseases affected the odds of KCN.
Main Outcome Measures
Odd ratios (OR) with 95% confidence intervals (CI) of KCN
Results
After adjustment for confounders, blacks (adjusted OR=1.57, CI: 1.38–1.79, p<0.001) had 57% higher odds and Latinos (adjusted OR=1.43, CI: 1.26–1.62, p<0.001) had 43% higher odds of being diagnosed with KCN compared with whites. Asians had 39% reduced odds (OR=0.61, CI: 0.50–0.75, p<0.001) of being diagnosed with KCN compared to whites. Patients with uncomplicated diabetes mellitus (DM) had 20% lower odds of KCN (adjusted OR=0.80, CI: 0.71–0.90, p=0.002) while patients with DM complicated by end-organ damage had 52% lower odds of having KCN (adjusted OR=0.48, CI: 0.40–0.58, p<0.001) compared to those without DM. Persons with collagen vascular disease had 35% lower odds of KCN (adjusted OR=0.65, CI: 0.47–0.91, p=0.01). Other conditions found to have increased odds of KCN included sleep apnea (adjusted OR=1.13, CI: 1.00–1.27, p=0.05), asthma (adjusted OR=1.31, CI: 1.17–1.47, p<0.001), and Down syndrome (adjusted OR=6.22, CI: 2.08–18.66, p<0.001). There was no association between KCN and allergic rhinitis, mitral valve disorder, aortic aneurysm, or depression (p>0.1, for all comparisons).
Conclusions
Clinicians caring for persons with KCN should inquire about difficulties with breathing or sleeping and, when appropriate, refer patients to undergo evaluation for conditions such as sleep apnea or asthma. Lower risk of KCN in those with DM, potentially due to corneal glycosylation, opens an interesting area of research.