Explaining the drop in cardiac death rates
In recent decades, cardiac mortality rates in the United States have been cut in half. Age-adjusted death rates from coronary heart disease (CHD) dropped from 543 in 100,000 deaths in 1980 to 267 in 2000. Satisfying as these figures are, physicians cannot simply bask in a warm glow; they need to know how this striking improvement came about. Is the it that physicians have gotten so good at implementing interventions for treating CHD? Does the answer lie in better drug therapy—the use of aspirin, beta blockers, and ACE inhibitors? Or should success in reducing cardiac risk factors get the lion's share of the credit? A recent statistical analysis sheds light on the answers to these questions.1
Study authors applied a statistical model called IMPACT to published data on the use and effectiveness of specific cardiac treatments and to changes in prevalence of known risk facts among US adults aged 25 to 84. Then the researchers distributed the difference between the observed and expected number of coronary deaths in 2000 among these treatments and risk factors.
The result? According to the analysis, credit should be divided about equally between treatment and risk reduction. Specifically,
- 47% of the decrease can be attributed to treatment. That figure breaks down to 11% resulting from secondary therapy after MI or revascularization, 10% for initial treatment of acute MI or unstable angina, 9% for treatment of heart failure, 5% to revascularization for chronic angina, and 12% to various other therapies.
- 44% of the decrease is attributable to reduction in risk factors: 24% to reductions in total cholesterol levels, 20% to lower systolic BP, 12% to reduction in smoking, and 5% to reduction in physical inactivity. Partially offsetting these reductions, however, were increases in 2 other risk factors: body mass index and diabetes.
This analysis suggests that future strategies to reduce cardiac death rates still further be based on a combination of effective therapy and active promotion of risk factor reduction through exercise programs, smoking cessation, and cholesterol control.
1. Ford ES, Ajani UA, Croft JB, et al. Explaining the decrease in U.S. deaths from coronary disease, 1980-2000. N Engl J Med. 2007;356(23):2388–2398.