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People who are underweight have a 40% higher risk of dying in the first month after surgery than patients who are overweight, according to new research released on Monday.
The findings suggest that body mass index (BMI) may be useful in predicting which patients are at the greatest risk while recovering from surgery, US researchers reported online today in the Archives of Surgery.
Prior studies looking at the role of BMI in surgery have been mixed, said Dr. George Stukenborg of the University of Virginia in Charlottesville, who worked on the study.
Using data from the American College of Surgeons National Surgical Quality Improvement Program, the researchers analysed nearly 190,000 patients who had major surgical procedures at 183 hospitals between 2005 and 2006.
Sicker to begin with
To look for a link between body weight and the risk of death, the researchers stratified patients into quintiles: BMI <23.1; BMI 23.1 to <26.3; BMI 26.3 to <29.7; BMI 29.7 to <35.3; and 35.3 or higher.
Overall, 3,245 (1.7%) patients died within 30 days of surgery.
"We found patients in the lowest quintile had 40% higher odds of death compared to the mid-range," said Dr Stukenborg.
Even after adjustment for type of surgery and other risk factors, patients with a low BMI still had a greater risk of dying in the first month after surgery compared to patients in the middle quintile.
Dr Stukenborg said it is not clear why. The study did not track recent weight loss, so it could be that people who weighed less were sicker to begin with.
Either way, he advises that doctors consider BMI in preoperative planning.
(Reuters Health, Julie Steenhuysen, November 2011)
