Does metformin use protect against the development of AMD?

The use of the antidiabetic drug metformin was associated with reduced odds of developing age-related macular degeneration (AMD), according to data from a large case-control study published in JAMA Ophthalmology. The greatest benefit was seen in patients on low to moderate doses.

This study included 312,404 patients aged >55 years with newly diagnosed AMD and 312,376 matched control participants. A total of 26% and 25.5% of patients had diabetes in the case and control groups, respectively.

Metformin use was associated with reduced odds of developing AMD (odds ratio [OR], 0.94 [95% CI, 0.92-0.96]); the association was dose dependent, with the greatest potential benefit found in patients on low to moderate doses. (dosages over 2 years: 1-270 g, OR, 0.91 [95% CI, 0.88-0.94]; 271-600 g, OR, 0.90 [95% CI, 0.87-0.93]; 601-1080 g, OR, 0.95 [95% CI, 0.92-0.98]).

There were no reduced odds of developing AMD in doses of >1080 g of metformin over 2 years.

In a cohort of only patients with diabetes, the reduction in odds ratio and the dose-dependent response were preserved. In patients with diabetes, the use of metformin was associated with a decreased OR of AMD, but it was a risk factor in patients with diabetic retinopathy (OR, 1.07 [95% CI, 1.01-1.15]). The authors concluded that “metformin may be useful as a preventive therapy for AMD and provides the basis for potential prospective clinical trials.”

Reference
Blitzer AL, Ham SA, Colby KA, et al. Association of metformin use with age-related macular degeneration: A case-control study. JAMA Ophthalmol. 2021; doi:10.1001/jamaophthalmol.2020.6331