Low-Dose Metformin Could Lower Risk of Age-Related Macular Degeneration

New research from the University of Chicago Medical Center suggests a common diabetes medication could help protect patients from the most common cause of blindness in older adults.

Results of the study, which included more than 300,000 participants aged 55 or older, suggest use of low dose metformin was associated with a lower incidence of age-related macular degeneration (AMD).

“Metformin was found to decrease the odds of new AMD among patients with diabetes and without diabetic retinopathy (DR), but this same outcome was not seen in patients with coexisting DR. To our knowledge, this is the largest study investigating the association between metformin and the development of AMD,” wrote study investigators.

With a multitude of studies suggesting metformin use was associated with lower risk of multiple age-related diseases, a trio of clinicians sought to determine whether metformin use was associated with lower risk of developing AMD. To do so, investigators designed their analysis as a case-control study of patients from the IBM MarketScan Commercial and Medicare Supplemental Databases from January 2006-December 2017.

All patients included in the study were 55 years of age and older and were diagnosed with AMD from January 2008-December 2017. In total, investigators identified 312,404 individuals were identified for inclusion. For the purpose of analysis, investigators also identified 312,376 control participants. Of note, the study’s case group was older, had a greater percentage of diabetics, and included more people from the northeast region of the US.

Upon analysis, use of metformin was associated with a reduction in odds of developing AMD (OR, 0.94l 955 CI, 0.92-0.96). Results of the analysis suggests this association was dose-dependent, with low to moderate doses of metformin being associated with the greatest benefit (1-270 g over 2 years: 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). When assessing doses greater than 1080 g, there was no association with reduced odds of developing AMD at 2 years.

Further analysis indicated both the reduction in odds ratio and the dose-dependent relationship were preserved in an analysis using a cohort consisting of only diabetic patients. Among patients with diabetes, metformin use was associated with a decreased risk of AMD in patients without existing diabetic retinopathy (OR, 0.93; 95% CI, 0.91-0.95), but was considered a risk factor for patients with existing diabetic retinopathy (OR, 1.07; 95% CI, 1.01-1.15).

“This case-control study using a large, national sample suggests that metformin use over 2 years in adults aged 55 years and older is associated with 5% to 10% reduced odds ratio of developing AMD. Moreover, there is a dose-dependent association of this potential protective effect, with low to moderate doses of metformin being associated with the lowest odds ratio for the development of AMD,” wrote investigators.

In their discussion, investigators note high doses of metformin are more typically used in patients with poorly controlled diabetes and this could have mitigated the positive benefits of use.

This study, “Association of Metformin Use With Age-Related Macular Degeneration: A Case-Control Study,” was published in JAMA Ophthalmology.