Heart Failure Linked to Obesity

Source: Tufts University
September 18, 2002 (Reviewed: September 3, 2004)

Extreme obesity is an established risk factor for heart failure, but it is not known if lesser degrees of overweight also increase the likelihood of this disease. Harvard researchers turned to data from the Framingham Heart Study for answers and published their findings in a recent issue of the New England Journal of Medicine.

The researchers followed 5,881 men and women participating in the ongoing Framingham Heart Study for an average of 14 years. At baseline, all were free of heart failure but were continuously monitored for the occurrence of cardiovascular events.

The primary outcome of interest was a first episode of heart failure, defined as the presence of two or more major conditions, including nocturnal dyspnea or orthopnea, jugular venous distention, pulmonary râles, acute pulmonary edema, and a 4.5 kg weight loss in response to heart failure treatment. Or, one major condition combined with two minor criteria such as ankle edema, nocturnal cough, dyspnea on ordinary exertion, and a heart rate of at least 120 beats per minute.

Participants were classified according to body mass index (BMI). A BMI of 18.5 - 24.9 was considered normal, 25 - 29.9 was overweight, and 30 or higher, obese. The relationship between BMI and disease outcome was examined by regression analysis.

Key findings

After controlling for potential confounders, the researchers found that as BMI increased, so did risk of heart failure. Women's risk increased 7% and men's risk 5% for each increment of 1 in BMI (hazard ratios 1.07; 95% CI: 1.04 - 1.10, p<0.001 and 1.05; 95% CI: 1.02 - 1.09, p=0.005). Compared to normal weight women, women who were overweight increased their disease risk by 50% and obese women doubled their risk (hazard ratios 1.50; 95% CI: 1.12 - 2.02, p<0.007 and 2.12; 95% CI: 1.51 - 2.97, p<0.001). The risk difference between normal and overweight men was non-significant. But men who were obese had a 90% increase in disease risk (hazard ratio 1.90; 95% CI: 1.30-2.79).

Interaction of health factors

The connection between obesity and heart failure is not surprising, given that being overweight is associated with high blood pressure, diabetes, and dyslipidemia. All may lead to myocardial infarction, a key predecessor to heart failure. In addition, hypertension and diabetes are independent risk factors for heart failure.

Note to clinicians

The population-attributable risk of heart failure in this study as a result of being overweight was 14% in women and 8.8% in men, meaning that excess weight was the direct cause of heart failure in these individuals. These are alarming statistics, especially as the number of overweight and obese people continues to grow. The authors of this study point to the threat of heart failure as an especially urgent reason for overweight patients to seek help in getting their weight under control.

Source

• Obesity and the risk of heart failure. S. Kenchaiah, JC. Evans, D. Levy,  et al., N Engl J Med, 2002, vol. 347, pp. 305--313

Related Links
Chronic Heart Failure in Older Persons
Diet and Exercise Help Keep Blood Pressure in Check
Excess Weight Adds Health Problems
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