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The Risk of Age-Related Macular Degeneration Is Reduced in Type 2 Diabetes Patients Who Use Metformin
Chin-Hsiao Tseng1,2,3
1Department of Internal Medicine, National Taiwan University College of Medicine, Taipei 10051, Taiwan.
Background:
Whether metformin may reduce the risk of age-related macular degeneration (AMD) requires confirmation. This study compared the risk of AMD between ever users and never users of metformin matched on propensity score (PS) in Taiwanese patients with type 2 diabetes mellitus.
Methods:
We enrolled study subjects from Taiwan's National Health Insurance. A total of 423,949 patients with new onset diabetes from 1999 to 2005 were identified. After excluding ineligible patients and enrolling only patients aged between 50 and 79 years, we created 13,303 pairs of ever users and never users of metformin matched on PS. The patients were followed from 1 January 2006 to 31 December 2011. We estimated hazard ratios by Cox regression.
Results:
AMD was newly diagnosed in 506 ever users and 639 never users. The respective incidence rates (per 100,000 person-years) were 778.72 and 1016.62. The hazard ratio (HR) and 95% confidence interval (CI) for ever versus never users was 0.756 (0.673-0.850). While ever users were categorized by tertiles of cumulative duration (<31.8, 31.8-63.9 and >63.9 months) and cumulative dose (<947.1, 947.1-2193.5 and >2193.5 g) of metformin, a dose-response pattern was observed. For the respective tertiles of cumulative duration, the HRs (95% CIs) were 1.131 (0.961-1.330), 0.821 (0.697-0.967) and 0.464 (0.384-0.561), while compared to never users. For the respective tertiles of cumulative dose, the HRs (95% CIs) were 1.131 (0.962-1.329), 0.739 (0.624-0.876) and 0.525 (0.438-0.629). A risk reduction among ever users was observed for all tertiles of defined daily dose but was most remarkable for the third tertile with a defined daily dose of >0.64. Subgroup analyses suggested that the benefit of metformin could be similarly observed among men and women and for age subgroups of 50-64 and 65-79 years. However, patients with diabetic retinopathy would not be significantly benefited and metformin did not seem to be preventive for exudative AMD.
Conclusion:
In general, metformin significantly reduces the risk of AMD.
Insights
Metformin use significantly lowers the risk of developing age-related macular degeneration (AMD) in patients with type 2 diabetes. This protective effect increases with longer duration and higher cumulative doses of metformin.
Area of Science:
- Ophthalmology
- Endocrinology
- Pharmacology
Background:
- Age-related macular degeneration (AMD) is a leading cause of vision loss.
- The potential protective effect of metformin, a common diabetes medication, against AMD is not well-established.
- This study investigated the association between metformin use and AMD risk in Taiwanese patients with type 2 diabetes mellitus.
Purpose of the Study:
- To compare the risk of developing AMD in patients with type 2 diabetes who have used metformin versus those who have never used it.
- To explore potential dose-response relationships between metformin usage (duration and cumulative dose) and AMD risk.
Main Methods:
- A retrospective cohort study using Taiwan's National Health Insurance data.
- Identified 423,949 patients with new-onset diabetes (1999-2005), aged 50-79.
- Matched 13,303 pairs of metformin ever-users and never-users on propensity score (PS) for analysis.
- Followed patients from 2006 to 2011, estimating hazard ratios (HR) using Cox regression.
Main Results:
- Metformin ever-users had a significantly lower risk of AMD (HR: 0.756; 95% CI: 0.673-0.850).
- A dose-response relationship was observed: longer duration and higher cumulative doses of metformin were associated with greater risk reduction.
- Benefits were consistent across genders and age groups (50-64, 65-79), but not observed in patients with diabetic retinopathy or for exudative AMD.
Conclusions:
- Metformin use is associated with a significant reduction in the risk of developing age-related macular degeneration in patients with type 2 diabetes.
- The protective effect of metformin against AMD appears to be dose-dependent.
- Metformin may not offer significant protection against AMD in patients with diabetic retinopathy or for the exudative form of AMD.
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