Long-Term Use of Metformin May Prevent AMD in Diabetes

TOPLINE: 

In patients with diabetes, using metformin for at least 5 consecutive years was associated with a lower risk of developing age-related macular degeneration (AMD), particularly the dry type of the condition.

METHODOLOGY: 

• Researchers conducted a retrospective cohort study using data from a federated health research network to examine the association between the use of metformin and the risk of developing AMD in patients with diabetes.
• They included 7496 patients aged 60 years or older with diabetes who attended two or more eye care visits at least 1 year apart; none had a diagnosis of AMD at or prior to every visit.
• Those who used metformin at least once per year for 5 or more consecutive years before their eye care visit (n = 3748) were compared with matched patients (n = 3748) who either used metformin for fewer consecutive years or never used it.
• The primary outcome was the development of AMD after the second eye care visit.

TAKEAWAY:

• The proportion of patients who developed AMD was lower among those who received metformin for 5 or more consecutive years than among those who did not (3.3% vs 4.9%).
• The use of metformin was associated with a 32% reduced risk for developing AMD (hazard ratio [HR], 0.68; 95% CI, 0.54-0.85); this association applied only to dry AMD (HR, 0.69; 95% CI, 0.53-0.90).
• Patients who used metformin for 6 or more consecutive years also had a reduced risk for developing AMD.
• The use of statins but not of insulin was also associated with a reduced risk for AMD.

IN PRACTICE:

“Yearly metformin exposure for at least 5 years was associated with a decreased risk of developing AMD, with significant differences observed in dry AMD and a non-significant trend in wet AMD,” the researchers reported.

“When individuals with a prior diagnosis of drusen were excluded from the cohort, these protective effects were not as pronounced. Although the presence of drusen signifies that the AMD disease process has already begun, these findings do not necessarily limit the potential utility of metformin. Rather, it remains possible that metformin could exert benefits throughout the disease course and not solely as a preventive measure before structural changes occur,” they added. 

SOURCE:

The study was led by Alexander T. Hong of the Keck School of Medicine of the University of Southern California in Los Angeles. It was published online Aug. 11, 2025, in Ophthalmology Retina.

LIMITATIONS:

Due to its retrospective design, the study could not show if taking metformin was actually protecting against AMD. There may have been coding errors and missing information as electronic health records data were used. The cohort analysis only included patients with annual health encounters for 5 years prior to the second eye care visit, potentially excluding those who changed institutions or had gaps in care. 

DISCLOSURES:

The study was partly supported by grants from the National Eye Institute, Research to Prevent Blindness, Inc, and All May See Foundation, Inc. One author disclosed receiving consulting fees and having personal financial interests with certain organizations unrelated to this study.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.