Why Do Overweight Patients Live Longer with Heart Failure?
By Annette M. Boyle
HOUSTON – Heart failure poses a conundrum – one the VA is eager to solve.
Now the leading cause of hospital admissions in the VA Health Care System, heart failure is associated with high mortality rates and poor quality of life. It also is increasingly common. At age 40, Americans have a 1 in 5 lifetime risk of experiencing heart failure. Nationwide, the number of hospitalizations associated with heart failure has increased 600% in the past 50 years, in part because of an aging — and heavier — population.
Obesity is a significant risk factor for heart failure as well as for common comorbidities such as hyperte
nsion and diabetes. Obesity and overweight affect nearly 80% of veterans. So, veterans should lose weight to reduce the risk of heart failure and reduce mortality rates, right? Maybe not.
While obesity increases the risk of heart failure, it also is associated with improved survival among patients with heart failure. Spontaneous weight loss associated with advanced heart failure has been proposed to explain this “obesity paradox.”
New research indicates, however, that the apparent protective effect of higher body mass index (BMI) in heart failure might be more complex, and might start earlier.
Drawing on data from the Atherosclerosis Risk In Communities (ARIC) study, researchers looked back at the BMIs of 1,487 heart failure (HF) patients four years before their diagnosis, then followed them for 10 years. Only 18% of all the patients in the study had normal BMIs prior to diagnosis; 35% had BMIs between 25 and 30 (overweight) and 47% were classified as obese, with BMIs exceeding 30.
Over the 10 years of the study, 43% of all patients died. Mortality rates varied significantly between the pre-diagnosis weight groups, with 51% of normal weight patients dying during the study period compared to only 38% of the obese patients and 45% of the overweight patients. Results of the study appeared in a recent issue of the Journal of the American College of Cardiology. 1
“Our study is novel in that we showed that higher pre-morbid BMI was independently associated with a survival advantage over a long follow-up period. Thus, weight loss due to advanced HF may not completely explain the protective effect of higher BMI in heart failure patients,” said the study’s senior author, Anita Deswal, MD, co-director of the heart failure program at the Michael E. DeBakey VA Medical Center and a professor at the Baylor College of Medicine in Houston.
The researchers found that the association of higher body weight with better survival rates was independent of patients’ demographic profiles, comorbidities, smoking status, history of cancer or diabetes.
The study adds significant new information to the understanding of the interaction of weight and heart failure. “Because prior studies used BMI that was measured in patients with established heart failure, they were unable to distinguish between the effect of weight loss between the time of development of HF and the BMI measurement, as a marker of more advanced HF (cardiac cachexia), vs. the possible survival advantage of pre-existing obesity or overweight,” Deswal told U.S. Medicine.
The survival benefit of obesity appears to decline over time, which the researchers attributed to complications from comorbidities. The protective advantage did not diminish over time for overweight HF patients.
Additional research may determine whether higher body weight is associated with protective effects such as greater metabolic reserves, as has been in seen in HIV/AIDS and cancer, or whether overweight or obese patients are simply diagnosed earlier in the disease progression. Alternatively, the higher prevalence of hypertension in overweight and obese HF patients might provide a benefit as it permits up-titration of some disease-modifying therapies, or elevated lipoproteins might provide protection by binding inflammatory mediators.
Ideal BMI for Heart Failure Patients?
In the meantime, should obese veterans at risk of or diagnosed with heart failure lose weight? The VHA PBM-MAP Clinical Practice Guideline: Pharmacologic Management of HF recommends that for veterans with heart failure “reducing weight if appropriate” might be beneficial. But, because of the lack of date demonstrating a benefit for that population, the American College of Cardiology and the American Heart Association do not specifically recommend weight loss for obese patients with heart failure.
Deswal noted that the current study “does not answer whether targeted weight reduction in obese patients with HF is beneficial or harmful,” as a randomized controlled trial would be needed to definitively resolve that question.
In an editorial accompanying the study in the Journal of the American College of Cardiology, Thomas Wang, MD, of Vanderbilt University Medical Center noted that determining whether an “‘optimal’ BMI for HF patients exists and whether interventions are warranted to maintain or achieve this BMI” requires a “better mechanistic understanding of what drives the obesity paradox” and the role of factors such as fat distribution, inflammation, fitness and insulin resistance on metabolic health. 2
Prior to development of heart failure, a clear recommendation may be easier to make. “Since obesity is associated with a higher risk of development of HF as well as more comorbidities such as hypertension, diabetes and sleep apnea, weight loss would still be advocated for better control of the comorbidities and possibly to decrease the risk of development HF in obese individuals, in general,” Deswal emphasized.
1 Khalid U, Ather S, Bavishi C, Chan W, Loehr LR, Wruck LM, Rosamond WD, Chang PP, Coresh J, Virani SS, Nambi V, Bozkurt B, Ballantyne CM, Deswal A. Pre-Morbid Body Mass Index and Mortality After Incident Heart Failure: The ARIC Study. J Am Coll Cardiol. 2014 Dec 30;64(25):2743-9.
2 Wang TJ. The Obesity Paradox in Heart Failure. J Am Coll Cardiol. 2014 Dec 30;64(25):2750-2.