Diabetes status, fasting glucose and HbA1c, and outcomes after myocardial infarction: a retrospective registry-based Swedish cohort study.

Abstract

This study aimed to assess cardiovascular (CV) risk across the full spectrum of dysglycaemia levels following myocardial infarction (MI). Retrospective registry-based cohort study. All patients with MI in Sweden registered in the cardiac rehabilitation registry within the Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART) between 2006 and 2017. In total, 47 558 patients over the age of 18 attending cardiac rehabilitation post-MI, with available information on glycaemic levels. The primary outcome was major adverse CV events (MACE), a composite of all-cause mortality, MI and ischaemic stroke until the end of follow-up (30 June 2018). Secondary outcomes included all the components of MACE, CV mortality and hospitalisation for heart failure. Pre-diabetes and possible diabetes were present in 20.6%, new-onset diabetes in 3.2% and known diabetes in 21.1%. During a median follow-up of 4.7 years, 9321 patients experienced MACE. A stepwise increase across glycaemic categories was observed, with HRs of 1.07 (95% CI 1.00 to 1.14) for pre-diabetes, 1.22 (95% CI 1.11 to 1.34) for possible diabetes, 1.22 (95% CI 1.08 to 1.37) for new-onset diabetes and 1.73 (95% CI 1.64 to 1.82) for known diabetes, compared with normoglycaemia. A near-linear association between fasting glucose and outcomes was observed across all patients, while glycated haemoglobin appears predictive mainly in those with established diabetes. Glycaemic disturbances early after MI, including hyperglycaemia below the diagnostic threshold for diabetes, are associated with a progressively higher risk of adverse outcomes. Beyond routine screening, these findings support close follow-up of at-risk patients, irrespective of diabetes status.