Background: Atrial fibrillation (AF) is the most frequent cardiac arrhythmia and is associated with an increased risk of thromboembolic events, heart failure, and frequent hospitalizations. Type 2 diabetes mellitus (T2DM) has one of the strongest associations with AF with an overall 35% increased risk. Metformin is the first-line medication for T2DM and it has been proposed to have anti-inflammatory, pro-metabolic and cardioprotective benefits, but its effect on AF is not well studied.

Our objective was to investigate whether the initial metformin monotherapy was associated with reduced AF rates compared to other non-insulin agents.

Methods: This retrospective cohort analysis involved adults with newly diagnosed T2DM between 2007 and 2017, without any history of arrhythmias or contraindications to metformin use including GFR less than 30 ml/min who initiated a single antidiabetes therapy (except insulin). A multivariate analysis was performed to control for other variables that may have impacted the association between initial therapy with metformin and the outcomes of interest.

Results: Out of 42384 cases with newly diagnosed diabetes, 5664 patients met the inclusion criteria. The majority of patients initiated monotherapy with metformin (81%), followed by sulfonylureas (13%) and thiazolidinediones (4%). The 10-year cumulative incidence of AF in the metformin group was 5.2% vs. 8.1% with others. Competing risk analysis did not demonstrate reduced rates of AF with metformin use (HR 0.92 95% CI 0.69 to 1.21; P = 0.55). Increased age and the presence of CHF were associated with significantly higher risk of AF (HR: 1.29, 95% CI: 1.21 to 1.37; P<0.001; HR: 2.73, 95% CI: 1.62 to 4.61; P<0.001, resp).

Conclusion: In this observational study following patients with newly diagnosed T2DM, first-line therapy with metformin, when compared to other non-insulin antidiabetes therapies, was not found to be associated with a decreased risk of developing AF.


Z. Tekin: None. A. Milinovich: Research Support; Self; Novartis AG, Novo Nordisk Inc. X. Ji: Research Support; Self; Merck & Co., Inc., Novo Nordisk Inc. J. Bauman: None. M. Kattan: Consultant; Self; GlaxoSmithKline plc. Research Support; Self; Boehringer Ingelheim (Canada) Ltd., Novo Nordisk Inc. K.M. Pantalone: Consultant; Self; Bayer Inc., Eli Lilly and Company, Merck & Co., Inc., Novo Nordisk Inc., Sanofi. Research Support; Self; Merck & Co., Inc., Novo Nordisk Inc. Speaker’s Bureau; Self; AstraZeneca, Merck & Co., Inc., Novo Nordisk Inc. R.S. Zimmerman: Research Support; Self; Bayer U.S., Merck & Co., Inc., Novo Nordisk A/S. Speaker’s Bureau; Self; LifeScan, Inc., Merck & Co., Inc. Stock/Shareholder; Self; Baxter, Bristol-Myers Squibb, Pfizer Inc., Procter & Gamble Company. M.K. Chung: None. S. Kashyap: Other Relationship; Self; GI Dynamics Inc.

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