Studies Conflict on Effect of Obesity on CHF Mortality

Linda Little

March 14, 2006

March 14, 2006 (Atlanta) — Two newly reported studies have conflicting views on whether obesity is associated with a lower risk of death in congestive heart failure (CHF). One study is consistent with previous studies that show a lower mortality risk, while the other study suggests that obese patients with CHF are actually at an increased risk of death.

Researchers from Baylor College of Medicine in Houston, Texas, confirmed earlier studies suggesting that at 1 year follow-up CHF patients who died were less likely to be obese or have metabolic syndrome than those who survived.

In contrast, researchers at the University of Michigan Health Systems in Ann Arbor, Michigan, reported that, similar to previous study results, CHF patients who are obese have more than 3 times the risk for the composite end point of death, cardiac transplantation, or ventricular assist device implantation.

Both studies were reported here in poster sessions at the American College of Cardiology 55th Annual Scientific Session.

The Michigan study not only showed that obese CHF patients had 3.35 times the risk of the combined study end point of death, cardiac transplantation, or ventricular assist device implantation than CHF patients who were of normal weight (P = .04). In addition, the study, which included 164 patients, showed that those who lost 10% of their body weight had 6.08 times the risk of the combined end point than those who had not lost weight (P = .009).

Moreover, those CHF patients with coronary disease had 10 times the risk of the combined end point as those without coronary disease. Other factors associated with higher risk were lower sodium and higher pulmonary wedge pressure.

The Michigan study was a retrospective look at a cohort of patients with ejection fraction of less than 40% who underwent at least 2 medically indicated right heart catherizations. Multivariable Cox modeling was undertaken to determine the effect of body mass index (BMI) on the risk for the composite end point.

Forty-one normal-BMI patients (71.9%) vs 58 overweight or obese patients (54%) reached the end point (P = .03). However, when the analysis was adjusted for those patients who had less weight loss (< 10%), the results were not significantly different, the researchers reported.

Audrey Wu, MD, from the Division of Cardiovascular Medicine and the lead researcher of the study, said that the results showed that weight loss was a significant predictor of the combined end point. "Obese patients also were at greater risk," she stated.

Researchers from Baylor College of Medicine also conducted a retrospective study to determine the prevalence of obesity and metabolic syndrome and their effects on mortality in patients hospitalized for CHF. The study included 1399 CHF patients from 3 Houston hospitals. Patients were considered to have metabolic syndrome if 3 of 5 criteria for the syndrome, including a BMI of more than 30 kg/m2, were met.

Of the 800 patients who were followed for more than 1 year and up to 5 years, the overall mortality rate was 63%. Those who died were less likely to be obese (32% vs 43%; P = .03) and less likely to have metabolic syndrome (35% vs 43%; P = .001) than those who survived.

Saamir Hassan, MD, the lead author of the study, commented that as the number of patients with metabolic syndrome increased, the number of deaths decreased.

The sicker patients might have more metabolic reserve by being obese, Dr. Hassan explained. "These patients have more medical problems as well so they may have better medical follow-up and are on more medications than the others," he told Medscape.

However, Dr. Hassan warned that the statistics are "raw data right now," adding that a multivariate analysis needs to be finished to see if the trend continues.

Robert Eckel, MD, president of the American Heart Association, said the observed protective effect of obesity in CHF is probably related to the fact that people who are losing weight are more apt to die.

Commenting on the Houston study, he told Medscape that "it's like losing weight if you are dying of cancer or heart disease. That explains why obesity is protective."

Dr. Wu also told Medscape that several previous research studies have shown survival benefit of obesity in heart failure patients, "which is totally counterintuitive."

Most of the previous studies that have shown that obesity is beneficial in CHF have taken a snapshot of the patient at a single time point, whereas the Michigan researchers studied patients who had undergone 2 prior right heart catherization at 2 separate times, she noted. "We had a definite volume status and weren't fooled by additional weight as a result of swelling," the University of Michigan researcher added.

ACC 55th Annual Scientific Session: Posters 964-57 and 964-95. Presented March 13, 2006.

Reviewed by Ariana Del Negro

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