Beta-blocker therapy for secondary prevention of myocardial infarction in elderly diabetic patients. Results from the National Cooperative Cardiovascular Project.

OBJECTIVES: We sought to determine the use and association with one-year mortality of beta-blocker therapy for the treatment of acute myocardial infarction (AMI) in elderly diabetic patients and to examine whether beta-blocker therapy was associated with increased rates of hospital readmission for diabetic complications traditionally associated with beta-blockers.
BACKGROUND: Although many randomized trials have demonstrated that beta-blockers are effective in reducing mortality after AMI, some experts are concerned about the use of beta-blockers in diabetic patients. Little is known about the effectiveness and complication rate of beta-blocker therapy after AMI for elderly diabetics in community practice settings.
METHODS: We conducted a retrospective cohort study using the National Cooperative Cardiovascular Project, which contained data abstracted from hospital medical records of Medicare beneficiaries admitted with an AMI during 1994 and 1995.
RESULTS: Out of 45,308 patients without contraindications to beta-blocker therapy, 7.4% were insulin-treated diabetics and 18.5% were non-insulin-treated diabetics. Beta-blockers were prescribed at discharge for 45% of insulin-treated diabetics, 48.1% of non-insulin-treated diabetics and 51% of nondiabetics (p < 0.001). After adjusting for demographic and clinical factors, diabetics continued to be less likely to receive beta-blockers at discharge compared with nondiabetics (odds ratio [OR] for insulin-treated diabetics 0.88, 95% confidence interval [CI] 0.82 to 0.96; OR for non-insulin-treated diabetics 0.93, 95% CI 0.88 to 0.98). After adjusting for potential confounders, beta-blockers were associated with lower one-year mortality for insulin-treated diabetics (hazard ratio [HR] = 0.87, 95% CI 0.72 to 1.07), non-insulin-treated diabetics (HR = 0.77, 95% CI 0.67 to 0.88) and nondiabetics (HR = 0.87, 95% CI 0.80 to 0.94). Beta-blocker therapy was not significantly associated with increased six-month readmission rates for diabetic complications among diabetics and nondiabetics.
CONCLUSIONS: Beta-blockers are associated with a lower one-year mortality rate for elderly diabetic patients to a similar extent as for nondiabetics, without increased risk of readmission for diabetic complications. Increasing the use of beta-blockers in elderly diabetic patients represents an opportunity to improve the care and outcomes of these patients after AMI.