Metformin and risk of age-related macular degeneration in individuals with type 2 diabetes: a retrospective cohort study

Abstract

BackgroundAge-related macular degeneration (AMD) in its late stages is a leading cause of sight loss in developed countries. Some previous studies have suggested that metformin may be associated with a reduced risk of developing AMD, but the evidence is inconclusive.AimsTo explore the relationship between metformin use and development of AMD among patients with type 2 diabetes in the UK.MethodsA large, population-based retrospective open cohort study with a time-dependent exposure design was carried out using IQVIA Medical Research Data, 1995–2019. Patients aged ≥40 with diagnosed type 2 diabetes were included.The exposed group was those prescribed metformin (with or without any other antidiabetic medications); the comparator (unexposed) group was those prescribed other antidiabetic medications only. The exposure status was treated as time varying, collected at 3-monthly time intervals.Extended Cox proportional hazards regression was used to calculate the adjusted HRs for development of the outcome, newly diagnosed AMD.ResultsA total of 173 689 patients, 57% men, mean (SD) age 62.8 (11.6) years, with incident type 2 diabetes and a record of one or more antidiabetic medications were included in the study. Median follow-up was 4.8 (IQR 2.3–8.3, range 0.5–23.8) years. 3111 (1.8%) patients developed AMD. The adjusted HR for diagnosis of AMD was 1.02 (95% CI 0.92 to 1.12) in patients prescribed metformin (with or without other antidiabetic medications) compared with those prescribed any other antidiabetic medication only.ConclusionWe found no evidence that metformin was associated with risk of AMD in primary care patients requiring treatment for type 2 diabetes.