Higher doses of metformin associated with lower risk for AMD
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A population-based, retrospective cohort study showed an association between metformin and a lower risk for age-related macular degeneration.
“We found that metformin was associated with a lower risk of AMD and that the risk-lowering trend was significantly associated with a higher dose of metformin,” Yu-Yen Chen, PhD, of the department of ophthalmology at Taichung Veterans General Hospital in Taiwan, and colleagues wrote in Journal of Ophthalmology.
Investigators included 68,205 patients (mean age 56.1 years) with type 2 diabetes from the Longitudinal Health Insurance Database between January 2001 and December 2013 in the study. The main independent variable of interest was metformin use. Researchers classified patients as metformin users if patients used the drug during the follow-up period.
They next evaluated whether the lower risk for AMD among users was dose responsive. Investigators used patient prescription records to analyze treatment duration, total dose and average dose of metformin.
Overall, 45,524 patients used metformin. The incidence of AMD was significantly lower in the metformin group (3.4%) vs. the non-user group (5.6%).
Results showed that age was a significant risk factor for AMD in both univariate and multivariate analyses (HR for patients older than 70 years vs. those younger than 50 years = 6.44). Patients with hypertension, hyperlipidemia, coronary artery disease and obesity had a significantly higher risk for developing AMD. The risk for AMD in patients with diabetic retinopathy significantly increased in both analyses (HR = 1.51).
Data revealed that longer duration of metformin use and higher total and average doses of metformin were associated with a lower risk for AMD.
“The underlying mechanism remains unclear but may be related to the antioxidative and anti-inflammatory properties of metformin,” the researchers wrote.
Chen and colleagues suggested further prospective studies and basic research be conducted to clarify possible explanations of the association between metformin and a lower risk for AMD development. – by Erin T. Welsh
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Arti Shah, OD, FAAO
Metformin, a first-line medication for the treatment of type 2 diabetes, is also known to decrease cardiovascular events, aid in fertility, retard aging and extend the lifespan in animals due to its antioxidative and anti-inflammatory properties. It seems logical to deduce that metformin could be associated with a lower incidence of AMD in patients with type 2 diabetes, with AMD being oxidative, inflammatory and an immune reaction. This is what Shen and colleagues set out to demonstrate in their retrospective study.
Although the exact mechanism of action of metformin on AMD is unknown, the researchers did show a lower risk for AMD with metformin use and a lower risk with a longer treatment period and higher total and average doses of metformin. While this could be quite optimistic, further studies are needed on a more diverse population incorporating various lifestyle factors and inclusive of additional laboratory tests including kidney function and glucose control, as the authors suggested. This will allow optometrists, who are at the forefront of comprehensive eye care in the U.S., to draw more concrete conclusions about the versatility of metformin in clinical practice. With further supporting studies, metformin might gain greater use for yet one more ailment as our profession continues to take on a larger role in diabetes management alongside our patient’s team of health care providers.
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