PURE: CV Risk Factors Greater, But CV Mortality Lower in High-Income vs. Low Income Countries

"My impression of this study was that there were a lot of potential compounding variables, age for instance as a risk factor. If life expectancy is lower in the third world, they're going to have less risk factors just on that basis. So some interesting data that need to be dissected out," said Tony DeMaria, MD, MACC.
Despite having higher risk factors for cardiovascular disease, people living in high-income countries are at lower risk for cardiovascular mortality, compared to people living in lower- or middle-income countries, according to results from the PURE study presented on Sept. 2 during the ESC Congress 2013 in Amsterdam.

The PURE study enrolled 155,245 subjects between 35 and 70 years old, from both rural and urban areas in 17 countries to assess the influence of cardiovascular risk factors on cardiovascular disease and mortality. Of those studied, 16,110 were from high income countries (primarily Canada but also Sweden and the United Arab Emirates), 104,260 subjects were from 10 middle-income countries, and 34,875 subjects were from four low-income countries (India, Bangladesh, Pakistan, and Zimbabwe). Subjects were were surveyed and followed for a mean of 3.9 years.

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Cardiovascular risk was calculated for each subject using the INTERHEART Risk Score (IHRS), and based on age, sex, smoking, diabetes, blood pressure, family history of heart disease, working heart rate, psychosocial assessment, diet and physical activity. In addition, treatment and prevention practices such as hypertension control, smoking cessation, use of lipid lowering drugs and secondary prevention were also tracked. Overall, the study found cardiovascular disease risk factors to be highest in high-income countries and lowest in low-income countries. In addition, treatment and preventive measures also followed this pattern (p<0.0001).

While hospitalizations for cardiovascular disease were highest in the high versus middle and low-income countries (P<0.05), the study authors noted that these hospitalizations were most often for non-major cardiovascular disease, compared to low-income countries where both fatal and other major cardiovascular disease (myocardial infarction, stroke and heart failure) were more common. Specifically, the rate of non-major cardiovascular disease in high-income countries was 4.3 per 1,000 person years, compared to 5.1, and 6.4 in middle and low-income countries (P<0.001). However, major cardiovascular disease occurred at a rate of 4.3 per 1,000 person years in high-income countries, compared to 5.1 and 6.4 in middle and low-income countries, respectively. Fatal cardiovascular disease occurred at a rate of 0.6 per 1,000 person years in high-income countries compared to 1.7 and 3.8 in middle and low-income countries, respectively.

"What this is telling us is that health care matters ... at least as much as risk factor control," said lead investigator Salim Yusuf, MD, professor of medicine of McMaster University's Michael G. DeGroote School of Medicine, vice president of research at the Hamilton Health Sciences and director of the Population Health Research Institute (PHRI) in Hamilton, Ontario, Canada. "Now the challenge is to identify those key aspects of health care that are effective and apply them to low and middle-income countries in a much more frugal manner."

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