Cardiac Mortality Drop Attributed to Therapies and Risk Factor Reductions

ATLANTA, June 6 -- Credit for the near halving of the rate of coronary disease deaths in the U.S, from 1980 to 2000, belongs equally to reductions in risk factors and to the rise of evidence-based therapies, found CDC and British researchers..

There were 341,745 fewer deaths from coronary heart disease in 2000 than in 1980, and about 47% of that decline can be attributed to primary and secondary medical therapies and interventions, they reported in the June 7 issue of the New England Journal of Medicine.

Reductions in risk factors such as smoking, high cholesterol, hypertension and inactivity get the nod for an additional 44% of the drop in coronary heart disease mortality, according to Earl S. Ford, M.D., M.P.H., of the National Center for Chronic Disease Prevention and Health Promotion, and colleagues.

But they also found that two major factors prevented the decreases in deaths from being even greater.

"Our analysis estimated that increases in the body-mass index accounted overall for about 26,000 additional deaths from coronary heart disease in 2000, and increases in the prevalence of diabetes for about 33,500 additional deaths; both figures are consistent with the results of other recent studies," they wrote. "Efforts to address these two risk factors should therefore receive particular attention in future measures to improve the public health."

The investigators used a previously validated statistical model called IMPACT to analyze the relative contributions of risk factor reduction, medical therapies, and interventions such as coronary artery bypass graft (CABG) and percutaneous transluminal coronary angioplasty to the decline in coronary disease-related deaths. The analyses were conducted at the University of Liverpool in England.

The difference between the expected and actual number of deaths from coronary heart disease in 2000 versus 1980 was distributed proportionally among the various treatments and risk factors included in the analyses.

They employed primarily data sources that were specific to the U.S. population, using the most up-to-date, least biased, and most representative sources whenever possible.

They found that the age-adjusted death rate for coronary heart disease among men fell from 542.9 deaths per 100,000 in 1980 to 266.8 per 100,000 in 2000. Among women, the rate fell from 263.3 per 100,000 in 1980 to 134.4 deaths per 100,000 in 2000. The total difference in observed vs. expected deaths in 2000 was 341,745.

About 47% of the decrease (159,330 fewer deaths) was attributed to treatments as follows:

• Secondary preventive therapies after myocardial infarction or revascularization, 11%
• Initial treatments for acute myocardial infarction or unstable angina 10%,
• Treatments for heart failure, 9%
• Revascularization for chronic angina, 5%,
• Other therapies 12%.

An additional 44% of the drop could be attributed to the following changes in risk factors (numbers represent percentage of total reduction, and overlap):

• Reductions in total cholesterol, 24%,
• Decrease in systolic blood pressure, 20%,
• Decline in smoking prevalence, 12%
• Reduction in physical inactivity, 5%.

Progress in risk factor reductions was partially offset, however, by an 8% increase in body-mass index over the two decades, by a 10% rise in the prevalence of diabetes, the authors noted.

"Irrespective of the assumptions used, we found that the largest contributions from medical therapies consistently came from secondary prevention, followed by treatments for acute coronary syndromes, then heart failure," they wrote. "Revascularization by means of CABG or angioplasty for stable or unstable disease together accounted for approximately 7% of the overall drop in deaths from coronary heart disease, a finding that is consistent with the results of previous studies in the United States and elsewhere."

They noted that possible study limitations included the use of data from various sources, including some studies that might have been limited by ethnic, geographic, or selections biases. They also noted that most of varying quality o and the averaging of interactions across broad groups, although the analyses were limited only to reductions in deaths, and did not include quality-of-life measures.