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Coronary Artery Death Rates Over the Last 20 Years
Abstract & Commentary
By Jonathan Abrams, MD, Professor of Medicine, Division of Cardiology, University of New Mexico, Albuquerque. Dr. Abrams serves on the speaker's bureau for Merck, Pfizer, and Parke-Davis.
Source: Ford ES, et al. Explaining the decrease in U.S. deaths from coronary disease, 1980-2000. N Engl J Med 2007;356:2388-2398.
Coronary deaths in the United States have dramatically declined since 1968. A new report consists of an analysis of mortality trends for coronary heart disease (CHD) mortality in the United States between 1980 and 2000, among U.S. adults 25 to 84 years of age. The document is a multi-authored analysis (United States and United Kingdom) that assesses the reasons behind the major decline in U.S. deaths from CHD during this 20 year period. The authors conclude that approximately half of the reduction in deaths is related to large decreases in the prevalence of major coronary risk factors over these 2 decades, while the other half is directly related to evidence based medical therapies. Extensive data sources are utilized, particularly the Impact Mortality Model, which incorporates major population risk factors for CHD as well as appropriate medical and surgical treatments. Data regarding the number of deaths in the United States were obtained from the U.S. Census Bureau. The analysis calculated the number of deaths from CHD that would have been expected in the year 2000 if CHD mortality rates remained unchanged since 1980. Thus, "The prevalence of the cases of CHD by diagnosis, the estimated frequency of use of specific treatments, the case fatality rate by diagnosis and the risk reduction due to the treatment, all stratified by age and sex, were obtained by public sources." Assessment of the number of deaths prevented or postponed as a result of multiple interventions was calculated. Extensive tables assess CHD clinical categories and their treatment, with estimates of the degree of deaths prevented or postponed by preventive approaches and/or specific therapies. Estimates of death reduction (total deaths as well as minimum and maximum estimates) were calculated. For example, the best estimate for aspirin reducing MI death was 2.3%; beta blockers 0.3%; ACE inhibitors 0.1%; and primary angioplasty 0.2%, for patients with acute myocardial infarction. For "secondary prevention after myocardial infarction," the same treatments were estimated to decrease death rates in year 2000 as follows: aspirin 1.5%; beta blockers 2.0%; ACE inhibitors 1.5%; statins (not available in the 1980 analysis) 1.4%. For chronic angina, the best estimate for deaths prevented or postponed related to CABG is 4.2%; statin therapy 0.3%, aspirin 0.3%. Angioplasty for chronic angina was estimated to reduce or prevent deaths by 1.3%. Tables in the manuscript present a large number of such estimates derived from the number of eligible, patients who received treatment, and were assessed for case fatality rates and absolute risk reduction. Conditions specifically explored in the overall assessment include acute myocardial infarction, unstable angina, secondary prevention after MI, chronic angina, heart failure, and hypertension.
The conclusion of this extensive analysis is that approximately half of the reduction or postponement of mortality over the 20-year period arose from medical and surgical treatments (46.6%). Favorable changes in risk factors were estimated to decrease or postpone mortality by 44%; total cholesterol reduction was robust, with a best estimate at 24%, and reduction of blood pressure at 20%. However, adverse outcomes were noted for increased BMI and diabetes, each of which resulted in an approximate 8%-10% increase in deaths.
Data from other countries, particularly New Zealand, Netherlands, the United Kingdom, are mostly comparable, with treatment responsible for approximately 35%-46% of mortality improvement and risk factors improvement responsible for approximately 44%-60%. The authors note that "the burden of CHD remains enormous, even though associated mortality rates fell by more than 40% between 1980 and 2000." They do not discuss specific advances in medical technology or pharmaceutical therapy, nor public health efforts to reduce the impact of major CHD risk factors. The concordance of this analysis with those from other countries is reassuring that the data are robust. Preventive oriented physicians and healthcare workers should take note of the major contributions of medical therapy from secondary prevention such as treatment of acute coronary syndromes and heart failure. Revascularization(CABG or PCI) in stable and unstable disease accounted for approximately 7% of the overall decline in deaths, consistent with other data. The authors underscore data showing an increase in CHD deaths in individuals with high body mass index as well as those with diabetes. An elevated BMI was calculated with a best estimate of 7.6% for an increase in deaths, and diabetes for a 9.8% increase in mortality. The authors conclude that "Future strategies for preventing and treating CHD should therefore be comprehensive, maximizing the coverage of effective treatments and actively promoting population-based prevention by reducing risk factors."
This study, although complex to report, is clearly good news. The fact that CHD mortality has decreased substantially over the 20-year period is certainly reassuring. As the population ages, and more individuals are alive who are in their 80s and 90s, the overall number of deaths may not decline proportionate to the analysis by the authors of the study, as the methodology used does not take into account the total number of deaths projected for older groups. Figure 1 of the manuscript looks at the number of deaths prevented or postponed according to age group and gender; in the 75-84 years of age population, there is a very large portion of the population with prevented or postponed deaths, indicating that preventive measures and risk factor reductions have had a major impact in the older population, a fact not emphasized in the manuscript. This report needs to be discussed by health professionals and made available to the general population. There is clear cut, unequivocal evidence that risk factor reductions, i.e., treatment of hypertension, hypercholesterolemia, etc, pays off in terms of deaths postponed or prevented. In addition, all of our therapies, both pharmacologic and interventional, have clearly changed outlook in a favorable direction for individuals with coronary heart disease. This report indicates that we are on the right track. One should assume that the better we emphasize prevention, the better we control risk factors. The better we use evidence-based approaches, both pharmacologic and invasive, the better the likelihood that the next analysis of 20-year mortality reduction will be even more positive.