HEART DISEASE Study: Lifestyle is leading factor
High levels of bad cholesterol and smoking accounted for two-thirds of the world's heart attacks.
TORONTO GLOBE AND MAIL
A landmark Canadian-led study has found that the causes of heart disease are the same in all people, regardless of age, sex, color, culture or where they live.
The unexpected conclusion, based on research involving nearly 30,000 people in 52 countries, upends the view that gender, genetics, or ethnicity plays a major role in determining who suffers a heart attack.
Even project leader Salim Yusuf, who has devoted much of his career to links between disease and ethnicity, was surprised to learn that it is largely nurture, not nature, that predicts who will fall prey to the world's No. 1 killer.
"I expected to find differences in risk factors based on ethnicities, which we did not find. But I also never expected that we'd be able to explain 90 percent of the global risk of heart disease," said Yusuf, director of the Population Health Research Institute at McMaster University and Hamilton Health Sciences Center.
The research team, which included colleagues from 262 centers around the world, concluded that high levels of bad cholesterol and smoking were by far the strongest predictors, accounting for two-thirds of the world's heart attacks.
These were followed by high blood pressure, diabetes, abdominal obesity, stress, a lack of daily fruits and vegetables and a lack of exercise.
Together, these nine risk factors, all of which hold the alluring promise of being changed or modified, accounted for 90 percent of heart-disease cases worldwide.
The finding "provides overwhelming proof to debunk" the so-called 50-percent myth, which suggests half the causes of heart disease are unknown because half the people who get it have no obvious risk factors, said study contributor Sonia Anand, a clinician and associate professor of medicine at McMaster.
The data also explode other myths and reveal remarkable trends in the incidence of heart disease.
Among them: Consuming more than three alcoholic drinks a week can moderately protect women from heart disease, a phenomenon other studies have already confirmed in men. Women tend to have their first heart attacks 10 years later than men. Having a paunch, or potbelly, is riskier than just being overweight.
For nonsmokers with good cholesterol levels, stress is the most powerful predictor of a heart attack.
Men in the Middle East and South Asia suffer first heart attacks 10 years younger than men in Western Europe or China, perhaps because of better prevention strategies in the West.
Cholesterol contributes to more than 74 percent of heart attacks in Africa.
Fully explaining these trends demands further study, and researchers have yet to take into account socioeconomic risk factors.
But Yusuf said the most exciting prospect at the moment is that "this information tells us how to prioritize public-health campaigns by region," since some risk factors are more common in certain populations.
In China, for example, smoking is the major culprit, contributing to more than a third of heart attacks. But obesity in China is remarkably low, accounting for less than 6 percent of cases.
In Western countries, where smoking rates are declining, countering abdominal obesity should be the priority since it explains roughly 60 percent of heart attacks.