Overweight and Obese Have Better One-Year Survival After Heart Attack
In a finding that leaves Duke University Medical Center researchers scratching their heads and planning further studies, it appears that overweight and obese heart attack patients have better intermediate-term survival rates than normal weight patients.
Additionally, since the researchers used data from two international trials that enrolled nearly 16,000 patients from 37 countries, the researchers also found that Asia had the highest percentage of normal weight people (58 percent), while the U.S. had the highest combined rate of obese and very obese (37 percent).
While it seems intuitive that the overweight and obese would do better than those who are very obese, the researchers paradoxically found that one year after a heart attack, the death rate for normal weight patients was 4.3 percent, compared to 2.7 percent for those overweight, 2.2 percent for the obese, and 2.6 percent for the very obese.
"We know that obesity is a risk factor for coronary artery disease, but no one has really studied its effect on intermediate-term outcomes in this high-risk set of patients," said Eric Eisenstein of the Duke Clinical Research Institute. He presented the results of the Duke study today April 1, 2003) during the 52nd annual scientific sessions of the American College of Cardiology.
"We tried adjusting the data for all the possible risk factors, patient characteristics and treatment choices we could come up with, but the effect persisted," Eisenstein continued. "We have already begun further analysis to better understand this phenomenon, as well as to gauge the economic impacts."
Eisenstein and colleague Duke cardiologist Kristin Newby, M.D., consulted the data collected from two related international trials, SYMPHONY and 2nd SYMPHONY (Sibrifaban vs. aspirin to yield maximum protection from ischemic heart events post-acute coronary syndromes), that enrolled a total of 15,904 patients at 931 sites around the world.
The researchers then grouped patients into one of four groups, normal, overweight, obese and very obese, based on what is called the Body Mass Index (BMI). The BMI is intended to take into account the relationship of weight and height. It is calculated by dividing weight in kilograms by height in meters squared. A BMI range of 18.5 to 25 is considered normal.
For their analysis, the Duke team eliminated 833 underweight patients (BMI less than 18.5) and ranked the remaining study participants according to their BMI group: normal (18.5 to 25); overweight (25 to 29.9); obese (30 to 34.9); very obese (greater than 35).
In addition to having the highest death rate after one year, normal weight patients also had the highest death rate (2.6 percent) after 90 days, as compared to overweight patients (1.6 percent), obese patients (1.3 percent), very obese patients (1.4 percent).
After only 30 days, normal weight patients had a death rate of 1.7 percent, compared to overweight patients (1.0 percent), obese patients (0.9 percent) and very obese patients (1.2 percent).
Interestingly, said the researchers, those patients considered overweight or obese tended to be younger and have a more adverse cardiovascular risk profile. They also tended to be treated more aggressively, which might partially explain their better outcomes.
In addition to having the highest rates of obese and very obese, the U.S. also has the smallest percentage of normal weight people.
Internationally, the percentage of normal, overweight, obese, very obese follow:
Australia/New Zealand - 26 - 47 - 20 - 7
Asia - 58 - 36 - 5 - 1
Latin America - 28 - 46 - 20 - 6
Eastern Europe - 29 - 48 - 18 - 4
Western Europe - 31 - 48 - 17 - 4
United States - 22 - 41 - 24 - 13
Canada - 23 - 47 - 23 - 7
While the overweight and obese appear to have this intermediate-term benefit, the researchers said their findings do not constitute an argument against weight reduction.
"This is particularly important given the epidemiological evidence that shows obesity is an independent predictor for the development of cardiovascular disease and is associated with the development of diabetes, high blood pressure and elevated lipid levels," Newby said. "Whether therapies targeted specifically at weight reduction will impact the development of coronary artery disease or clinical outcomes after heart attack remains to be proven in randomized clinical trials."
Both of the SYMPHONY trials were funded by F. Hoffmann-La Roche, Basel, Switzerland. The Duke team's analysis was supported by the Duke Clinical Research Institute.
CHICAGO - DukeMed News