Metformin linked to lower odds of developing AMD in non-diabetic patients

Use of metformin was associated with lower odds of developing age-related macular degeneration (AMD) among patients without a diabetes diagnosis, offering more evidence of a possible role for the inexpensive drug in eye health, according to a case-control study. After adjusting for risk factors for AMD, use of metformin was associated with reduced odds of any AMD development, as well as reduced odds of developing dry AMD, reported Dimitra Skondra, MD, PhD, of the University of Chicago, and colleagues. 

They also found a dose-dependent relationship between metformin use and AMD: 2-year cumulative metformin doses of 1 to 270 g, 271 to 600 g, and 601 to 1,080 g were associated with 20%, 19%, and 12% lower odds for developing AMD, respectively, they noted in JAMA Ophthalmology. There were similar trends when they focused on dry AMD — the milder form of the disease versus wet AMD. Compared with no metformin use, 2-year cumulative doses of 1 to 270 g and 271 to 600 g were linked to 18% and 14% lower odds of dry AMD development.

The findings from this study are “very encouraging” and provide support for launching a randomized trial, Skondra told MedPage Today. “We saw a signal in patients who don’t have diabetes. If we did show that taking metformin for 4-5 years decreased the risk of more advanced AMD, we could target millions of patients around the world.”

Amitha Domalpally, MD, PhD, of the University of Wisconsin-Madison, who was not involved in the study, told MedPage Today that a limitation to this study was the lack of data about possible confounders like diet, body mass index, and smoking. While she noted that the study was well done, it doesn’t prove that metformin prevents AMD. It’s possible that patients taking it for reasons other than diabetes — such as prediabetes and weight control — were already taking steps to improve their health and therefore lower their risk of AMD.

Both Skondra and Domalpally acknowledged the challenges involved in launching a prospective randomized trial for metformin and AMD. For now, both said there’s not enough evidence to support prescribing metformin to prevent AMD.

Source: Randy Dotinga, MedPage Today, December 7, 2023; see source article