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 physiological 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 the Journal of the American Medical Association.
"Identifying the underlying factors associated with [the overall decline in heart disease] is critical for planning future health policy, and prioritizing strategies for primary and secondary prevention," the authors wrote.
Harindra C. Wijeysundera, MD, of the Sunnybrook Health Sciences Centre in Toronto, and colleagues used a model to analyze the relative risks of CHD and quantify the relationship between CHD mortality and evidence-based therapies in eight distinct CHD sub-populations:
- acute MI (AMI),
- acute coronary syndromes,
- secondary prevention post-AMI,
- chronic coronary artery disease,
- heart failure in the hospital,
- heart failure in the community,
- primary prevention for hyperlipidemia, and
- primary prevention for hypertension.
Researchers also analyzed population trends in six risk factors: smoking, diabetes mellitus, systolic blood pressure, plasma cholesterol level, exercise and obesity.
The primary outcome measure was the number of deaths prevented or delayed in 2005; secondary outcome measures were improvements in medical treatments and trends in risk factors.
They 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 aged 75 to 84 years.
The data showed that improvements in medical and surgical treatments were associated with 43 percent of the total mortality decrease, most notably in chronic stable coronary artery disease (17 percent of the total), heart failure occurring while in the community (10 percent) and AMI (8 percent).
Researchers noted that in 1994, 8 percent of patients with chronic stable coronary artery disease were taking statins compared with 78 percent in 2005, and 29 percent of heart failure patients were taking beta-blockers in 1994 compared with 67 percent in 2005.
Trends in risk factor treatment accounted for 3,660 fewer CHD deaths prevented or delayed (48 percent of the total), specifically reductions in total cholesterol (23 percent) and systolic blood pressure (20 percent).
The authors also found 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," they wrote.