Trends in absolute and relative risk of acute myocardial infarction in people with type 2 diabetes in Scotland: a national retrospective cohort study

Abstract

BackgroundWhether more rigorous monitoring and evidence-based treatment of type 2 diabetes has led to improvements in cardiovascular outcomes is unclear. We aimed to explore trends in incidence rates of acute myocardial infarction in the Scottish adult population with type 2 diabetes compared with the non-diabetic population. MethodsIncidence rates of acute myocardial infarction (first admissions and deaths in and out of hospital) between Jan 1, 2001, and Dec 31, 2010, for adults aged 35–84 years were derived from Scottish Morbidity Records and linked death records. Diabetes diagnoses were ascertained by linkage to the Scottish diabetes register. Trends were analysed with negative binomial regression adjusted for age and an area-based measure of socioeconomic deprivation, and then expressed as annual percentage change in rates. FindingsOf 118 340 incident acute myocardial infarctions, 15 798 (13%) were in people with type 2 diabetes 1·88 million (4%) of 50·7 million person-years at risk were in people with type 2 diabetes. In men and women with and without type 2 diabetes, incidence of acute myocardial infarction decreased over time. Incidence was higher among people with than without type 2 diabetes, with higher relative risks in women than in men. The mean annual fall in rate of acute myocardial infarction was 3·7% (95% CI 3·2–4·2) and 2·3% (2·0–2·7) in women and men without diabetes, respectively; and 5·6% (4·6–6·7) and 4·4% (3·6–5·2) in women and men with type 2 diabetes. Relative risks for acute myocardial infarction declined for people with type 2 diabetes compared with people without type 2 diabetes from 1·5 (1·4–1·7) to 1·2 (1·1–1·3) for men and 1·8 (1·6–2·1) to 1·5 (1·3–1·6) for women between 2001 and 2010. InterpretationRates of acute myocardial infarction decreased over time in all population groups with more pronounced declines among people with than without type 2 diabetes. Secular trends in risk factors and improved primary and secondary prevention of cardiovascular disease are potential explanations for the observed time trends. FundingData linkage of the Scottish population-based register of people with diagnosed diabetes to national hospital admission and mortality records and data management was funded by the Scottish Government through the Scottish Diabetes Group, which had no role in the writing of the abstract or the decision to submit for publication.