Antihyperglycemic therapy and cardiovascular outcomes after acute myocardial infarction in elderly patients with diabetes.

Objective: Type 2 diabetes mellitus is a clear prognostic marker for increased cardiovascular morbidity and mortality after acute myocardial infarction (AMI). We compared diabetes patients based on therapy used (no pharmacotherapy, those prescribed oral antihyperglycemic agents and those prescribed insulin) on the composite risk of recurrent AMI, congestive heart failure and mortality among elderly patients with AMI.

Methods: Using administrative data, we identified patients, aged 65 years and older, with an incident AMI hospitalization in British Columbia and the Calgary Health Region between April 1, 1995, and March 31, 2002, for a retrospective cohort study. Cox proportional hazard models were constructed to compare time to reach the composite outcome in the treatment groups.

Results: Among 22 499 patients with AMI, 5158 patients had diabetes. Women comprised 43.2% of the diabetes cohort. For the composite outcome, there was a stepwise increase in the occurrence based on medication use: no diabetes (23.55 events per 100 person-years); diabetes but no treatment (31.70 per 100 person-years); oral agents only (36.34 per 100 person-years) and insulin therapy (49.43 per 100 person-years). After adjustment, relative to patients without diabetes, no treatment (hazard ratio 1.37, 95% confidence interval, 1.22 to 1.53), oral agents only (hazard ratio 1.43, 95% confidence interval, 1.31 to 1.56) and insulin therapy (hazard ratio 1.65, 95% confidence interval, 1.48 to 1.84) were all associated with an increased risk of the outcome developing.

Conclusions: Diabetes conferred a significant risk increase in a combination of cardiovascular events after AMI. The risk existed even for diabetes patients not prescribed therapy and showed a progressive trend as the intensity of treatment advanced toward insulin.