Metformin And Glaucoma: Cohort, Meta-Analysis, And Mendelian Randomization

A recent study reports that metformin use was associated with a possible lower glaucoma risk across three complementary analyses in people with diabetes. The study package included a prospective cohort analysis in 24,206 UK Biobank participants with diabetes who were free of glaucoma at baseline. Investigators also performed a random-effect meta-analysis that synthesized published human cohort evidence on metformin and glaucoma incidence. They further examined metformin’s genetically proxied effects using a drug-target Mendelian randomization approach, weighting variants near five metformin target genes by their associations with HbA1c. Across the cohort, meta-analytic, and genetic analyses, results were reported as consistent with a possible protective association between metformin use and glaucoma among patients with diabetes, with key analyses limited to individuals of European ancestry.

In the cohort component, investigators reported that metformin use was associated with lower incident glaucoma risk among participants with diabetes in the prospective dataset. The reported hazard ratio was 0.81 (95% confidence interval, 0.67 to 0.97; P=0.019). All cohort participants were free of glaucoma at enrollment, keeping the analysis focused on newly identified rather than existing disease. In that baseline-eligible diabetic group, the hazard estimate reflected a lower reported risk among metformin users during follow-up. Considered on its own, the cohort analysis described an association between metformin exposure and incident glaucoma risk in this population.

The random-effect meta-analysis of human cohort studies showed a similar direction of association. The pooled estimate was a risk ratio of 0.81 (95% confidence interval, 0.72 to 0.93; P=0.002). This synthesis extended the pattern beyond the single prospective cohort to a broader set of available human observational data. Its focus remained glaucoma incidence among people with diabetes, aligning with the clinical context of the cohort findings. The pooled estimate therefore matched the observational direction reported in the cohort analysis.

In the drug-target Mendelian randomization analysis, investigators used proxies for five metformin target genes and primary open-angle glaucoma summary data from European-ancestry participants, with genetic effects scaled to a per–standard deviation reduction in HbA1c. The genetic estimate yielded an odds ratio of 0.66 (95% confidence interval, 0.46 to 0.94; P=0.022). This component added a genetically informed analysis that pointed in the same direction as the human observational findings. The authors concluded that the cohort, pooled, and genetic results together suggest a potentially protective association between metformin and glaucoma risk in diabetes among these participants. They stated that randomized clinical trials are needed to evaluate metformin as preventive glaucoma therapy, based on their interpretation of the convergent evidence.

Key Takeaways

• In the cohort analysis (European-ancestry participants), metformin use was associated with a lower risk of incident glaucoma.
• The meta-analysis and drug-target Mendelian randomization findings pointed in the same direction as the cohort result.
• The authors concluded that the combined findings suggest a possible protective association and called for randomized trials.