The new reports appear in Wednesday’s Journal of the American Medical Association. They provide evidence that challenges the “50 percent” claim that became conventional wisdom “even though the original source of this claim is not well-documented,” says a JAMA editorial that accompanied the studies.
The studies “have enormous public health implications,” the editorial continues.
“[T]hese studies emphasize that to reduce the burden of cardiovascular disease, physicians should have even greater vigilance in identifying conventional [coronary heart disease] risk factors and must redouble efforts to control them effectively,” wrote Drs. John Canto and Ami Iskandrian of the University of Alabama at Birmingham.
One study analyzed data from three previous multiyear studies that surveyed nearly 400,000 U.S. patients. Among 40- to 59-year-old participants who died of heart disease including heart attacks, at least 87 percent had one or more conventional risk factors. Among participants with nonfatal heart attacks, such risk factors were present in 92 percent of men aged 40 to 59 and 87 percent of women in that age group.
Simply having one of the risk factors does not, however, mean that a person will develop heart disease. The study also reported that between 58 to 85 percent of study participants who did not develop heart disease also had one of the four risk factors.
Some of these participants may have had heart disease that had not been diagnosed and others may have benefited from genetic or environmental factors that protected them from developing it, according to the study authors.
The second study, which analyzed surveys from outside the United States, found that at least 85 percent of roughly 120,000 patients with heart disease had at least one of the four risk factors. At least one major risk factor was found in about 85 percent of women and 80 percent of men with heart disease including heart attacks.
Dr. Umesh Khot, a co-author of the study who is now with Indiana Heart Physicians in Indianapolis, told the Associated Press that the results underscore the importance of conventional risk factors but do not mean other factors are insignificant.
That sentiment is echoed in a third JAMA report, which analyzed dozens of studies on four bloodstream components cited as “emerging risk factors”: C-reactive protein, lipoprotein-a, fibrinogen and homocysteine.
There is little evidence that any of these are superior to conventional risk factors in determining heart disease risk, said study authors Drs. Daniel Hackam and Sonia Anand of McMaster University.
Dr. Augustus Grant, the American Heart Association’s president, said the new studies reinforce what most doctors already know — that preventing major risk factors “can have a substantial impact on the incidence of disease.”
“As we explore other potential” factors, Grant told the Associated Press, “we are not expecting to find a dramatic new source for the risk.”