A South Korean study of over 3.5 million adults found that patients with age-related macular degeneration had an 11% increased risk of developing rheumatoid arthritis, suggesting a potential link between eye and joint health.
In the large-scale longitudinal cohort study, published in Scientific Reports, investigators found that patients with age-related macular degeneration (AMD) had an 11% increased risk of developing rheumatoid arthritis compared with those without age-related macular degeneration. The study analyzed data from 3.5 million participants over a mean follow-up period of 9.9 years.
The investigators utilized data from the National Health Information Database (NHID) of South Korea, which covers health care utilization, health screening, sociodemographic factors, and mortality for the entire Korean population. The study included individuals aged 50 years and older who underwent health checkups in 2009 and were followed until 2019.
AMD was identified using the International Classification of Diseases 10th revision (ICD-10) code H353, registered by an ophthalmologist in the year prior to health screening. Visual disability was determined based on certification from the Ministry of Health and Welfare of Korea.
RA was defined as a new diagnosis with ICD-10 codes M05 (seropositive RA) or M06 (seronegative RA), along with a prescription for disease-modifying anti-rheumatic drugs.
Cox regression analysis was used to estimate hazard ratios (HR), adjusting for various covariates including age, sex, income, place of residence, body mass index, smoking habits, alcohol consumption, regular exercise, diabetes, hypertension, dyslipidemia, and Charlson comorbidity index.
Among the key findings were:
- Patients with AMD had an adjusted HR of 1.11 (95% confidence interval [CI] = 1.02–1.21) for developing rheumatoid arthritis (RA) compared with controls.
- Patients with AMD without visual disability showed a higher risk (adjusted HR = 1.13, 95% CI = 1.03–1.23) of RA.
- Patients with AMD with visual disability did not show a significantly increased risk (adjusted HR = 0.90, 95% CI = 0.64–1.27) of RA.
- The association remained significant after adjusting for age, sex, lifestyle factors, and comorbidities.
Among the total participants, 41,412 (1.17%) had AMD at baseline. During the follow-up period, 43,772 patients (1.24%) were diagnosed with RA. The cumulative incidence of RA was significantly higher in the AMD group compared with controls.
Baseline characteristics showed that patients with AMD were more likely to be female, older, nonsmokers, and nondrinkers; have a higher income; reside in rural regions; and have a diagnosis of hypertension, diabetes, or dyslipidemia (all P < .001).
Among the 41,412 patients with AMD, 3,014 (7.28%) had visual disability at the time of their health screening. Compared with patients with AMD without visual disability, those with visual disability were more likely to be male, older, current smokers, and heavy drinkers; have a lower income; reside in rural regions; and have a diagnosis of diabetes.
Stratified analyses revealed that age, sex, and the presence of comorbidities (hypertension, diabetes, or dyslipidemia) showed no significant interactive effect with AMD on RA development (P for interaction > .05).
A sensitivity analysis defining RA using only ICD-10 codes yielded similar results, with the HR of RA in the AMD group (1.14, 95% CI = 1.11–1.18) comparable to the original definition using both ICD-10 codes and prescriptions.
The investigators noted several limitations of the study, including potential selection bias, reliance on claims data for disease identification, lack of certain inflammatory markers in the analysis, and the inability to establish causality as a result of the observational nature of the study.
The authors declared no competing interests.
