Obesity Paradox Seen in Stroke as Well

A new study suggests that the inverse relationship between obesity and better survival rates that exists for heart failure (HF), acute myocardial infarction (MI), and bypass surgery also applies to stroke.

Researchers at the Center for Stroke Research (CSB; Berlin, Germany), the University of East Anglia (Norwich, United Kingdom), and other institutions conducted a post hoc analysis of data from 4,428 patients with acute stroke or transient ischemic attack (TIA). Body mass index (BMI) was available in 1,521 patients of these patients, who were categorized as underweight (BMI under 18.5 kg/m²), normal (BMI 18.5 to 25), overweight (BMI 25 to 30), obese (BMI 30 to 35), advanced obesity (BMI over 35), and no body weight assessed. Outcome measures after 30 months were all-cause mortality and nonfatal outcomes that included recurrent stroke, the need for institutional care, and functional impairment.

The results showed that the mortality risk was lower in overweight patients, and lowest in the obese and very obese patients, compared with normal BMI. Functional outcomes, nonfatal outcomes, and recurrent stroke followed the same inverse pattern; underweight patients had the worst outcomes but obese patients had better outcomes than patients with normal BMI. After adjustment for multiple confounding factors, mortality was significantly lower in obese patients (all BMI above 30 kg/m²) than patients with normal weight were; obese patients also had a lower risk of institutional care, high dependency, and recurrent stroke. Underweight patients had consistently the highest risks for all endpoints. The study was published early online on October 16, 2012, in the European Heart Journal.

“It's not clear how excess fat might be protective after a stroke. All we do know so far is that there's an association between body weight and outcome; we don't have a lot of reliable data to explain this finding,” said lead author Wolfram Doehner, MD, PhD, of the CSB. “It may be that a body carrying extra pounds has more reserves to fight off disease, but there might also be a molecular explanation of how the weight can exert a beneficial effect.”

The obesity survival paradox was first described in 1999 in overweight and obese people undergoing hemodialysis, and has subsequently been found in those with HF and peripheral artery disease (PAD). In people with HF, those with a BMI between 30 and 34.9 had lower mortality than those with a normal weight. This has been attributed to the fact that people often lose weight as they become progressively more ill. Similar findings have been made in other types of heart disease.

Related Links:
Center for Stroke Research
University of East Anglia