Improvement in coronary heart disease risk factors linked to lower rate of CHD death

From 1994 to 2005 in Ontario, Canada, there was a 35 percent decrease in the rate of deaths from coronary heart disease (CHD), with about half of this reduction associated with improvements in traditional CHD risk factors such as total cholesterol levels and systolic blood pressure, according to a study in the May 12 issue of JAMA.

"Coronary heart disease remains the most common cause of death worldwide and generates a large economic burden. Rates of CHD mortality have decreased substan­tially over the last 3 decades. Identifying the underlying factors associated with this decline is critical for planning future health policy, and pri­oritizing strategies for primary and sec­ondary prevention," the authors write.

Harindra C. Wijeysundera, M.D., of the Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, and colleagues conducted a study to determine the association of CHD prevention and treatment strategies with the de­cline in CHD mortality in Ontario. The study, which included individuals ages 25 to 84 years, used a model that integrates data on population size, CHD mortal­ity, risk factors and changes in the use of treatments. The researchers analyzed the relative risks and quantified the relationship between CHD mortality and (1) evidence-based therapies in 8 distinct CHD subpopulations (acute myocardial infarction [AMI; heart attack], acute coronary syndromes, secondary prevention post-AMI, chronic coronary artery disease, heart failure in the hospital vs. in the community, and primary prevention for hyperlipidemia or hypertension) and (2) population trends in 6 risk fac­tors (smoking, diabetes mellitus, systolic blood pressure, plasma cholesterol level, ex­ercise, and obesity).

The researchers found that between 1994 and 2005, the age-adjusted CHD mortality rate in Ontario decreased by 35 percent, from 191 to 125 deaths per 100,000 inhabitants, translating to an estimated 7,585 fewer CHD deaths in 2005. The de­crease was concentrated in older patients ages 75 to 84 years. Risk factor changes were associated with 48 percent of the total mortality decrease (accounting for an estimated 3,660 fewer CHD deaths), and new medi­cal and surgical treatments were asso­ciated with 43 percent of the decrease (and an estimated 3,280 of the total deaths prevented or delayed).

The most substantial con­tributions regarding new medi­cal and surgical treatments came from the management of patients with chronic stable coronary artery disease (1,305 fewer deaths; 17 percent of total). In 1994, 8 percent of patients with chronic stable coronary artery disease were tak­ing statins compared with 78 percent in 2005. Improvements in the treatment of pa­tients with heart failure in the commu­nity were associated with approximately 750 fewer deaths (10 percent of total). In 1994, 29 percent of pa­tients were taking beta-blockers com­pared with 67 percent in 2005. Improve­ments in the treatment of AMI patients represented 8 percent of the overall deaths prevented or de­layed.

Over the study period, there was a reduction in the average total cholesterol level of the Ontario population, with 1,730 CHD deaths being prevented or delayed associated with this reduction, representing 23 percent of the overall reduction in CHD mortality. There was also a decrease in average sys­tolic blood pressure from 1994 to 2005 for this population, which was associated with 1,545 fewer deaths (20 percent of total) after subtracting deaths prevented due to advances in pharmaco­logical therapies.

The authors add that increasing diabetes prevalence and body mass index had an inverse relationship associated with higher CHD mortality of 6 percent and 2 percent, respectively.

"Although our study was not designed to establish a causal rela­tionship between these trends and mortality, these results may inform decision making at all levels with the goal of ensuring that the gains in CHD mor­tality reduction during the previous de­cade are not lost in the next decade."