April 3, 2003 (Chicago) -- Among heart researchers there is no disagreement: Obesity and being overweight increase the risk for heart attacks. Period. But a new study is adding an unexpected element to the obesity story: Compared with normal weight people, overweight and obese people are more likely to survive heart attacks.
The study, from researchers at Duke University, tracked heart attack outcome in 16,000 patients from 37 countries and determined that about 4% of normal-weight people die within a year of heart attack, "but the one-year death rate drops to just over 2% for obese patients," says lead researcher Eric Eisenstein, DBA, of the Duke Clinical Research Institute in Durham, N.C.
Overweight and obese people also had better 30-day and 90-day heart attack survival rates than normal-weight people, says Eisenstein. Even one year after the heart attack, obese and overweight people had a higher heart attack survival rate than normal-weight people.
The researchers say the data also confirm other studies that point to Americans' expanding waistlines: 37% of Americans in the study were obese or very obese while more than half of the Asian patients were normal weight.
Eisenstein tells WebMD that the new finding was not only unexpected, it is also unexplained. "It was surprising. We really don't know why we are seeing this association. Several years ago we did a similar study analyzing data from about 9,000 patients treated at Duke. In that study we found no association with body mass."
With America now home to more overweight and fewer normal-weight people than any other country, these findings might be considered good news. But Eisenstein says that is not the take-home message because while obese people had a heart attack survival advantage, "this is a short-term finding. We are reporting deaths within a year of heart attack. We don't know about long-term survival."
Moreover, he says that overweight patients "were younger when they had their first heart attack, so this confirms other studies that link obesity to heart attack risk." This age difference may be a factor in heart attack survival, says Eisenstein. "Older age in normal-weight patients could contribute to mortality," he says. Another factor could be treatment: Overweight patients received more aggressive treatment than normal-weight patients.
Robert H. Eckel, MD, professor of physiology and biophysics at the University of Colorado Health Sciences Center in Denver, tells WebMD that it would be a mistake for people to interpret these results as proof that obesity is heart healthy.
He expressed some skepticism about the results since there could be "confounding factors that are not taken into account." For example, he says that more of the normal-weight patients could be smokers, which is another significant risk factor. Moreover, he says that studies based on analysis of medical records often lead to incorrect conclusions. One example would be medical record review studies that concluded hormone replacement therapy prevented heart disease, a finding that was contradicted in a study that compared hormones with dummy pills. In that study, women taking hormones actually increased their risk for heart disease.
Eisenstein agreed that the findings are "not conclusive, but they do suggest the need for more study. If there is some protective mechanism associated with obesity, we need to identify it."