BACKGROUND: Dual anti-platelet treatment with clopidogrel and aspirin is indicated for most patients after myocardial infarction. We examined the risk/benefit relationship of dual anti-platelet treatment according to age in a nationwide cohort of 30,532 myocardial infarction patients without revascularization.

METHODS: Patients admitted with first-time myocardial infarction in 2002-2010, not undergoing revascularization, were identified from nationwide Danish registers. Dual anti-platelet treatment use was assessed by claimed prescriptions. Stratified into age groups, risk of bleeding, all-cause mortality and a combined endpoint of cardiovascular death, recurrent myocardial infarction and ischaemic stroke was analysed by Cox proportional-hazard models and tested in a propensity-score matched population.

RESULTS: A total of 21,302 users and 9230 non-users of dual anti-platelet treatment were included (mean age 67.02 (±13.8) years and 64.7% males). Use of dual anti-platelet treatment decreased with age: 80% (<60 years), 76% (60-69 years), 66% (70-79 years) and 52% (>79 years). We found a reduced risk of cardiovascular death, recurrent myocardial infarction and ischaemic stroke in users <60 years (Hazard ratio (HR) =0.69; 95% confidence interval (CI) 0.59-0.80), 60-69 years (HR=0.64; 95% CI 0.56-0.73), 70-79 years (HR=0.80; 95% CI 0.72-0.89) and >79 years (HR=0.92; 95% CI 0.84-1.01, NS). Risk of bleeding increased with dual anti-platelet treatment use in patients aged <60 years (HR=1.63; 95% CI 1.17-2.26), 60-69 years (HR=1.22; 95% CI 0.97-1.59, NS), 70-79 years (HR=1.42; 95% CI 1.17-1.72) and >79 years (HR=1.46; 95% CI 1.22-1.74). Similar tendencies in all four age groups were found in the propensity-matched population.

CONCLUSION: Dual anti-platelet treatment use was less likely among elderly patients although similar effects regarding both risk and benefit were found in all age groups. Increased focus on initiating dual anti-platelet treatment in elderly, non-invasively treated myocardial infarction patients is warranted.