The “Obesity Paradox”: Bigger Girth Means Lessened Risk of Cardiac Death

After generations of warnings that obesity is one of the biggest risk factors for heart failure and cardiovascular disease, a University of Rochester study says that it’s actually skinny people who run a higher risk of sudden death from cardiac failure. Scientists at the University of Rochester Medical Center in New York found that non-obese patients who suffered heart failure had a 76 percent greater risk of sudden cardiac death than obese patients.

The “non-obese” category included underweight, normal weight, and overweight-but not obese-patients, based on body mass index. The study used the clinical definition of obesity as a BMI of 30+. Overweight was defined as a BMI of 25 to 29, and normal and underweight were defined as 25 or below. When overweight patients were factored out, the researchers were startled to find that underweight and normal-weight patients ran a 99 percent higher risk of sudden cardiac failure than obese patients.

The study, presented recently in Atlanta at the American College of Cardiology’s Annual Scientific Session, is the first to assess the relation between BMI and the risk of sudden cardiac death.

Researchers tracked 1,231 patients who had previously experienced at least one bout of heart failure. Some of them later became obese, a condition that would seemingly increase their chance of subsequent heart failure. The study findings showed, however, that a lower BMI was more closely associated with an increased risk of sudden cardiac death than an increased BMI.

These findings, though perhaps surprising to the general public, hew closely to something that cardiologists have known about for some time: the “obesity paradox,” in which obese patients stand a better chance of avoiding death from heart failure than their thinner counterparts.

So the question for researchers is why obese people, who for years have been considered at very high risk for stroke or heart attack, seem to enjoy a greater immunity to heart failure than people whose weight puts less strain on their cardiovascular systems?

One tentative answer offered by researchers, who acknowledge that a definitive answer will require more study, is simple genetics. Eric Hansen, co-lead author of the study and a second year medical student at the University of Rochester, said that there may be a genetic reason, noting that obese patients generally do not eat well or exercise properly, and that many smoke. He theorizes that because their bodies are already surviving bad treatment, they are more resistant to heart failure.

Sudden cardiac death is a condition in which the heart suddenly stops beating. Unless the heart is restarted and the circulation of oxygen throughout the body is restored within minutes, the victim dies. An estimated 330,000 Americans die from the condition each year-about half of all heart-related fatalities.

Cardiac arrest is attributed to abnormal heart rhythms that can be brought on scarring from previous heart attacks or arterial blockage. In a related study, the University of Rochester researchers looked into the effects of BMI on the effectiveness of implantable cardioverter defibrillators. An ICD is a small pager-sized unit that is surgically implanted in the chest to detect irregular heart beats. When it detects a faulty rhythm, the device can send a shock to the heart to make it return to normal. The researchers found that ICDs were most effective in people with lower BMIs.

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As girth grows, risk of sudden cardiac death shrinks

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