Glaucoma correlates with increased risk of Parkinson's disease in the elderly: a national-based cohort study in Taiwan

Background/objective: Very little is known about the association between glaucoma and Parkinson's disease in the elderly. The objective of this study was to determine whether glaucoma is associated with Parkinson's disease in older people in Taiwan. Methods: A retrospective cohort study was conducted to analyze the Taiwan National Health Insurance Program database from 2000 to 2010. We included 4330 subjects aged 65 years or older with newly diagnosed glaucoma as the glaucoma group, and 17,000 randomly selected subjects without a glaucoma diagnosis as the non-glaucoma group. Both groups were matched for sex, age, other comorbidities, and index year of glaucoma diagnosis. The incidence of Parkinson's disease at the end of 2011 was measured. A multivariable Cox proportional hazard regression model was used to measure the hazard ratio and 95% confidence intervals for Parkinson's disease associated with glaucoma. Results: The overall incidence of Parkinson's disease was 1.28-fold higher in the glaucoma group than that in the non-glaucoma group (7.73 vs. 6.02 per 1000 person-years; 95% confidence interval 1.18, 1.40). After controlling for potential confounding factors, the adjusted hazard ratio of Parkinson's disease was 1.23 for the glaucoma group (95% confidence interval 1.05, 1.46), compared with the non-glaucoma group. Conclusions: Older people with glaucoma correlate with a small but statistically significant increase in the risk for Parkinson's disease. Whether glaucoma may be a non-motor feature of Parkinson's disease in older people requires further research to confirm.