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Thin patients have higher risk of dying after surgery

By  Rachael Rettner


While being trim is generally good for your health, it may actually raise the risk of death after surgery, recent research suggests.

In one study, slender people with a body mass index (BMI) of 23 or less were 40 percent more likely to die within a month of a surgical procedure, compared with those who were overweight, with a BMI between 26 and 29, the researchers said.

The results held even after the researchers took into account the condition the patient had that required surgery, and the risk of death associated with that surgery.

That study is published in the March issue of the journal Archives of Surgery.

The findings agree with those of several other recent studies. In a study published last week in the Journal of Cardiothoracic and Vascular Anesthesia, 20 percent of underweight patients who had coronary artery bypass surgery died in the hospital, compared with 3 percent of obese patients (though the researchers noted far fewer patients in the study were underweight).

And in a study published in February in the journal Colorectal Disease, low BMI was a risk factor for dying after colon surgery.

Low BMI should be recognized as an important risk factor for death following surgery, study researcher George Stukenborg, of the University of Virginia’s School of Medicine, said in an interview with MyHealthNewsDaily in November. Doctors should take into account thinness when planning a patient's care after surgery, and should tell thin patients about their increased risk of death, Stukenborg said.

Death after surgery

In their study, Stukenborg and colleagues analyzed information from more than 189,500 patients from 183 medical centers who underwent surgery between 2005 and 2006.

The researchers divided patients into five groups based on BMI. They calculated the risk of death for each group, as compared with the risk of death for those in the middle group (who had a BMI between 26.3 and 29.7).

About 3,200 patients died within 30 days of surgery. Among those with a BMI of 23.1 or less, 2.8 percent died within 30 days, whereas 1.5 percent of patients with a BMI between 26.3 and 29.7 died.

There was no difference in the risk of death between patients who were overweight, and patients who were obese or very obese, the researchers found.

Why the link?

This study cannot tell us why thin people are at an increased risk of death after surgery, Stukenborg said. One idea is that these patients may be more frail, or may have recently experienced weight loss, Stukenborg said.

In the study published last week, underweight patients were at higher risk of intestinal bleeding, pneumonia, a prolonged stay in the intensive care unit and need for a blood transfusion compared with those who were obese.

People with a BMI of under 18.5 are generally considered underweight, and in the studies, they were included with patients who had BMIs between 19 and 24, who were of normal weight.

People who fall along the extremes of the weight spectrum, both underweight and morbidly obese, are at increased risk for complications after surgery, said Dr. Nestor de la Cruz-Munoz, chief of bariatric surgery, University of Miami School of Medicine. Underweight people likely represent a sicker population with underlying medical conditions, de la Cruz-Munoz said.

"As soon as you drop below your ideal weight, you get into a group of people who are malnourished," and not well in general, de la Cruz-Munoz said. People in this population may not have adequate levels of protein in their bodies to properly heal in areas that have been operated on, he said.