Incidence of myocardial infarction in elderly men being treated with antihypertensive drugs: population based cohort study

OBJECTIVE: To analyse the association between use of antihypertensive treatment, diastolic blood pressure, and long term incidence of ischaemic cardiac events in elderly men. DESIGN: Population based cohort study. Baseline examination in 1982-3 and follow up for up to 10 years. SETTING: Malmŏ, Sweden. SUBJECTS: 484 randomly selected men born in 1914 and living in Malmŏ during 1982. MAIN OUTCOME MEASURES: Observational comparisons of incidence rates and rate and hazard ratios of ischaemic cardiac events (myocardial infarction or death due to chronic ischaemic cardiac disease). RESULTS: The crude incidence rate of ischaemic cardiac events was higher in those subjects who were taking antihypertensive drugs than in those who were not (rate ratio 2.6 (95% confidence interval 1.7 to 3.9)). After adjustment for potential confounders (differences in baseline smoking habits, blood pressure, time since diagnosis of hypertension, ischaemic or other cardiovascular disease, hypercholesterolaemia, hypertriglyceridaemia, diabetes mellitus, obesity, and raised serum creatinine concentration) this rate was reduced but still raised (hazard ratio 1.9 (1.0 to 3.7)). In men with diastolic blood pressure > 90 mm Hg, antihypertensive treatment was associated with a twofold increase in the incidence of ischaemic cardiac events (rate ratio 2.0 (1.1 to 3.6)), which vanished after adjustment for potential confounders (hazard ratio 1.1 (0.5 to 2.6)). In those subjects with diastolic blood pressure < or = 90 mm Hg, antihypertensive treatment was associated with fourfold increase in incidence (rate ratio 3.9 (2.1 to 7.1)), which remained after adjustment for potential confounders (hazard ratio 3.8 (1.3 to 11.0)). CONCLUSION: Antihypertensive treatment may increase the risk of myocardial infarction in elderly men with treated diastolic blood pressures < or = 90 mm Hg.