Increased risk of subsequent myocardial infarction in patients with type 2 diabetes: a retrospective cohort study using the U.K. General Practice Research Database.

OBJECTIVE To compare the risk of subsequent myocardial infarction (MI) between patients with and without type 2 diabetes mellitus (T2DM) in a retrospective cohort study. RESEARCH DESIGN AND METHODS Patients with their first MI recorded in the U.K. General Practice Research Database in 1997-2008 were classified as T2DM, diagnosed before or within 28 days after the date of the first recorded MI (i.e., the index date), or non-T2DM. Patients diagnosed within 28 days after the index date were assumed to have developed T2DM at baseline (i.e., before the index date). The primary outcome was the first subsequent MI. The secondary outcomes were all-cause death and a composite of all-cause death or subsequent MI. Cox proportional hazards models were fit to obtain hazard ratios (HRs) for all outcomes. RESULTS A total of 7,411 T2DM (median age 72 years; men 63.4%) and 48,726 non-T2DM patients (median age 69 years; men 65.3%) were included. The crude incidences (per 1,000 patient-years) in T2DM vs. non-T2DM were 32.8 vs. 22.8 for subsequent MI, 83.7 vs. 52.1 for all-cause death, and 106.5 vs. 69.9 for the composite end point. The adjusted HRs for subsequent MI, all-cause death, and their combination were 1.41 (95% CI 1.27-1.56), 1.50 (1.41-1.60), and 1.42 (1.34-1.50), respectively, in women and 1.23 (1.14-1.34), 1.40 (1.33-1.47), and 1.33 (1.27-1.39) in men. CONCLUSIONS Compared with non-T2DM, T2DM was associated with an increased risk for subsequent MI, all-cause death, and their composite end point. The risk tends to be higher in women than in men.