Dahlqvist S, et al. - This prospective case-control study aimed to investigate the risk of atrial fibrillation in people with type 1 diabetes compared with matched controls from the general population. In men with type 1 diabetes, the risk of atrial fibrillation was slightly raised, while for female patients it was 50% higher compared with the general population. Among people with type 1 diabetes, the risk of atrial fibrillation increased with renal complications and poor glycaemic control.

• The design of this research was a prospective case-control study.
• It included individuals with type 1 diabetes in the Swedish National Diabetes Registry who were each matched with 5 controls for age, sex, and county of residence.
• They were randomly selected from the Swedish Population Register.
• The physicians obtained cases of atrial fibrillation from the Swedish National Patient Registry.

• Between Jan 1, 2001, and Dec 31, 2013, the physicians followed up 36258 patients with type 1 diabetes and 179980 controls.
• For patients, median follow-up was 9·7 years (IQR 5·2–13·0) and 10·2 years (5·7–13·0) for controls.
• With an adjusted hazard ratio (HR) of 1·13 (95% CI 1·01–1·25; p=0·029) in men and 1·50 (1·30-1·72; p<0·0001) in women (p=0·0019 for interaction), 749 (2%) individuals with type 1 diabetes and 2882 (2%) controls were diagnosed with atrial fibrillation.
• In individuals with type 1 diabetes, the excess risk of atrial fibrillation increased with worsening glycaemic control and renal complications.
• They noted no excess risk of atrial fibrillation in men with type 1 diabetes who had HbA_1c lower than 9·7% (<83 mmol/mol) or in women with type 1 diabetes who had HbA_1c lower than 8·8% (<73 mmol/mol) among individuals with normoalbuminuria.