Having a lower body mass index appears to increase the risk of death within a month after surgery, new research finds. (Image: Abel Mitja Varela/iStockphoto.com)

Being obese increases the risk of developing a variety of diseases and conditions that can lead to premature death. But being obese also appears to be protective against dying when a person undergoes a surgical procedure.

An article appearing today in the Archives of Surgery by researchers from the University of Virginia in Charlottesville looked at 30-day mortality data involving 189 533 general and vascular surgical procedures reported in 2005 and 2006. The researchers found that overall, 1.7% of patients died within 30 days of their surgery. But 2.8% of those with a body mass index (BMI) of less than 23.1 died within a month of surgery (a BMI of 18.5 to 24.9 is considered normal) while only 1% of those with a BMI of 35.3 and above died in that time frame (a BMI above 30 is considered obese). Even when controlling for a variety of factors, including age and comorbidities, patients with a BMI under 23.1 were 40% more likely to die following a surgery than those with a BMI of 26.3 or higher.

George J. Stukenborg, PhD, MA, an associate professor at Virginia and a coauthor of the article, discusses his team’s findings:

“We wanted to reevaluate the relationship between body mass index and mortality risk in a population of surgery patients. The standard definitions for categories—underweight, normal, overweight, and obese—come from population studies, and it is from those data that we attribute health benefits and risks to the general healthy population. We found that those criteria did not fit this population of surgical patients.

“It’s true that patients in the low BMI group [the study population was divided into quintiles] had a 40% higher odds of dying than those in the middle group [BMI of 26.3 to less than 29.7]. We also found that patients with large values of BMI in the fourth or fifth quintiles [29.7 to less than 35.3 or 35.3 and above, respectively] did not have any significantly higher risk of death compared with the middle group.

“Unfortunately we cannot answer from our data why lower BMI was associated with increased mortality. It may be because the lower group may include those who are more frail. But regardless of why, lower BMI should be recognized by surgeons for 30-day mortality and that should be taken into account during preoperative decision making and in planning follow-up for patients once they are discharged.”

Categories: Obesity, Surgical Interventions