Metformin may have a protective effect against AMD


Metformin, a frequently prescribed drug to treat diabetes, could be a novel therapy for AMD.

Reviewed by Dimitra Skondra, MD, PhD.

Metformin may have a protective effect against AMD

A frequently prescribed drug to treat diabetes, metformin, may have the potential to be a novel therapy for age-related macular degeneration (AMD), reported Dimitra Skondra MD, PhD. She is Associate Professor of Ophthalmology and Visual Science, and Director of the J. Terry Ernest Ocular Imaging Center, Founder/Leader, Retina Microbiome Team, Vitreoretinal Service, The University of Chicago.

This protective effect is known to be present against other age-associated diseases, but the importance of such a finding in diabetes cannot be over-emphasized.

She and her colleagues conducted a retrospective case-control study to take a close look at the the relationship betweenmetformin and other antidiabetic medications in patients with AMD. The authors used a large health insurance claims database to identify patients who had been newly diagnosed with AMD between January 2008 and December 2017.

A total of 312,404 patients and 312,376 matched controls were included in the study.

Important finding: Metformin associated with reduced odds of AMD development

Dimitra Skondra MD, PhD

Dimitra Skondra MD, PhD

“We found that metformin use was associated with reduced odds of developing AMD (odds ratio [OR], 0.94 [95% CI, 0.92-0.96]), Dr. Skondra reported.

The low-to-moderate doses of metformin carried the greatest potential benefit. The former covers doses of 1-270 grams/2 years; OR, 0.91 [95% confidence interval [CI], 0.88-0.94]; and the latter 271-600 grams/2 years; OR, 0.90 [95% CI, 0.87-0.93]).

In contrast, doses that exceeded 1,080 grams/2 years were not associated with reduced odds of developing AMD.

Both the reduced ORs and the dose-dependent response were preserved in the diabetic patients-only cohort, that is, metformin was associated with a decreased OR of development of AMD in patients with diabetes who did not have diabetic retinopathy (OR, 0.93 [95% CI, 0.91-0.95]); however, this was not the case when patients also had diabetic retinopathy (OR, 1.07 [95% CI, 1.01-1.15]).

Another finding in the patients in the diabetic cohort was an independent protective effect against AMD development associated with the use of insulin (OR, 0.92 [95% CI, 0.90-0.95], P < 0.001), and sulfonylureas (OR, 0.94 [95% CI, 0.92-0.96], P < 0.001). When analyzed in combination with metformin versus neither of those medications, insulin (OR, 0.89 [95% CI, 0.83-0.97], P = 0.004) and sulfonylureas (OR, 0.91 [95% CI, 0.84-0.98], P = 0.01), the analysis showed a protective effect as well.

“Subjects taking insulin or sulfonylureas alone had a similar risk of developing AMD as those taking metformin alone (OR, 0.96 [95% CI, 0.89-1.01] and OR, 0.98 [95% CI, 0.90-1.05), respectively). Patients receiving exenatide, sitagliptin (Januvia, Merck), or pramlintide (Symlin, Bristol-Myers Squibb), other diabetic medications, had a higher risk of developing AMD (OR, 1.08 [95% CI, 1.05-1.11], P < 0.001), although when taken with metformin the increased risk was no longer seen (OR, 1.04 [95% CI, 0.97-1.13]).

Another finding was that subjects taking sulfonylureas with metformin had an even greater decreased risk of AMD development compared to those taking metformin alone (OR, 0.94 [95% CI 0.91-0.97], P < 0.001).

Dr. Skondra concluded,These data suggest that metformin may be a novel AMD therapeutic strategy and provide the basis for future studies.”

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