Do obese people fare better after heart attacks?
Everyone knows being overweight and obese increases the risk of heart disease, right? And yet, in several studies over the past 10 years, these patients have been found to fare better following a heart attack or coronary angioplasty (a procedure to open blocked arteries) than their normal-weight counterparts.
Referred to as the "obesity paradox," this finding has left medical researchers and doctors scratching their heads.
New research may help to resolve this conundrum. "The obesity paradox is a confusing finding," said Jennifer Tremmel, MD, a cardiovascular fellow, who recently completed two studies with David P. Lee, MD, assistant professor of medicine, and Richard E. Shaw, PhD, of Sutter Pacific Heart Centers.
The studies, which involved analyses of the American College of Cardiology's extensive National Cardiovascular Data Registry, show that after statistically adjusting for multiple factors such as age and diabetes, there remains a strong unidentified contributor to death among the overweight and obese. This contributor essentially eliminates the paradoxical benefit that has been seen in the overweight and obese, and is suspected by the researchers to be obesity itself.
The bottom line, says Tremmel, is this: "Being overweight or obese certainly increases your risk of developing coronary artery disease, and it also likely contributes to your mortality once you have a heart attack and undergo angioplasty, especially the higher your weight is."
While conducting the studies, researchers also uncovered an interesting variation in gender mortality rates. It appears that being overweight has more of an adverse affect on women who have heart attacks and undergo angioplasties than it does on men. To put it bluntly, it appears to be even worse for women's heart health to be overweight than it is for men's.
One of the studies, which was presented at the American Heart Association annual meeting in November, evaluated 93,483 patients who had large heart attacks and underwent coronary angioplasty. The other study was presented at the Transcatheter Cardiovascular Therapeutics annual conference in October and investigated 346,876 patients who had smaller, or "near," heart attacks and underwent coronary angioplasty.
Results from both studies showed that the obesity paradox essentially disappeared after statistical adjustment for mortality risk factors. Both studies also showed a higher mortality risk due to excess weight in women compared to men.
Researchers compared mortality rates based on Body Mass Index, or BMI, a measure of body fat based on height and weight. Women with a BMI between 25 and 30—which places them in the overweight category—were at a greater risk of dying because of their excess weight than men with the equivalent BMI. The mortality rate increase didn't occur in men until they reached a BMI above 30, which places them in the obese category.
"We don't know why this is," Tremmel said. "We definitely need more research conducted on women."