Background: Individuals with diabetes are at higher risk of myocardial infarction than non-diabetics. However, much less is known about the incidence of, and risk factors for, development of diabetes and impaired fasting glucose in patients who have had a myocardial infarction. We set out to estimate this incidence and investigate whether lifestyle factors such as dietary habits might alter this risk.
Methods: We used prospectively obtained data for 8291 Italian patients with a myocardial infarction within the previous 3 months, who were free of diabetes (determined by medication use, a physician-reported diagnosis, or fasting glucose > or =7 mmol/L) at baseline. Incidence of new-onset diabetes (new diabetes medication or fasting glucose > or =7 mmol/L) and impaired fasting glucose (fasting glucose > or =6.1 mmol/L and <7 mmol/L) were assessed at follow-up at 0.5, 1.0, 1.5, 2.5, and 3.5 years. Baseline data for body-mass index (BMI), other risk factors, dietary habits, and medications were updated during follow-up. A Mediterranean diet score was assigned according to consumption of cooked and raw vegetables, fruit, fish, and olive oil. Associations of demographic, clinical, and lifestyle risk-factors with incidence of diabetes and impaired fasting glucose were assessed with multivariable Cox proportional hazards.
Findings: During 26 795 person-years (mean follow-up 3.2 years [SD 0.9]), 998 individuals (12%) developed new-onset diabetes (incidence 37 cases per 1000 person-years). Of the 7533 without impaired fasting glucose at baseline, 2514 (33%) developed new-onset impaired fasting glucose or diabetes (incidence 123 cases per 1000 person-years), rising to 3859 (62%) of 6229 with the lower cutoff for impaired fasting glucose of 5.6 mmol/L (incidence 321 cases per 1000 person-years). Independent risk factors for new-onset diabetes or impaired fasting glucose included older age, hypertension, use of beta-blockers, lipid-lowering medications (protective), and diuretic use. Independent lifestyle risk-factors included higher BMI, greater BMI gain during follow-up, current smoking, a lower Mediterranean dietary score, and wine consumption of more than 1 L/day. Data for physical activity were unavailable, but inability to perform exercise testing was associated with higher incidence of diabetes and impaired fasting glucose.
Interpretation: Compared with population-based cohorts, patients with a recent myocardial infarction had a higher annual incidence rate of impaired fasting glucose (1.8 vs 27.5% in our study) and diabetes (0.8-1.6% compared with 3.7%) in this study. Thus, our results indicate that myocardial infarction could be a prediabetes risk equivalent. Smoking cessation, prevention of weight gain, and consumption of typical Mediterranean foods might lower this risk, which emphasises the need for guidance on diet and other lifestyle factors for patients who have had a myocardial infarction.