Effect of starting metformin on severe and long COVID-19 among people living with type 2 diabetes in England: a new user cohort study in OpenSAFELY-TPP

Starting metformin monotherapy within 6 months of new type 2 diabetes diagnosis in England is linked to slightly higher COVID-19-related hospitalisation or death (HR 1.17, 95% CI 1.02–1.35).

• Why it matters: Earlier observational work using prevalent-user designs may be biased, while randomized trials suggest little mortality effect; a large new-user estimate for severe and Long COVID was missing.
• What they did: Using OpenSAFELY-TPP linked NHS records, adults aged 18–85 newly diagnosed with T2D (Aug 2018–Aug 2019) were followed from 6 months post-diagnosis for up to 2 years, comparing metformin starters versus no antidiabetic drug.
• The result: The intention-to-treat 2-year risk difference was 0.36% (95% CI 0.09–0.62), Long COVID was imprecise (HR 1.39, 95% CI 0.83–2.33), and positive-control diabetes-related death was elevated (HR 1.41), suggesting unmeasured confounding.

AI summary of the abstract · may contain errors · not medical advice · read the paper.