In the second study, low BMI was spotlighted as increasing risk of death within 30 days of surgery. The research, published in the Archives of Surgery, found that, of the nearly 190,000 patients included in the study, 1.7 percent of them died within 30 days of surgery. Deaths among patients with a BMI less than 23.1 were twice that of patients with a BMI of 35.3 or higher.
"Patients with low body mass index are at significantly higher risk of death with 30 days after following general and vascular surgical procedures," said Dr. George Stukenborg, associate professor of public health sciences at University of Virginia's School of Medicine. "Low BMI should be taken into account as an important risk factor for risk of death within 30 days of the procedure."
Oddly, patients in the heavier BMI groups did not have "a statistically significant mortality risk," said Stukenborg.
Patients who underwent laparatomy, or a procedure involving a large incision through the abdominal wall, were at highest risk of death after surgery, compared witho other operations.
Stukenborg said the research does not disclose why BMI is a risk factor for death, but experts say the higher amount of deaths could be among the frail and elderly, not the young, thin and healthy. Stukenborg said he and his colleagues plan to investigate reasons for the increased risk in upcoming studies.