In traumatic accident injuries, obesity may affect survival

Critically injured accident victims are more likely to die or have worse outcomes if they are obese, researchers have reported, although the reasons aren’t exactly clear.

A study of 242 patients admitted to L.A. County and USC Medical Center’s critical care and trauma unit in 2002 showed that those with body mass indexes of 30 or higher were twice as likely to die as their thinner counterparts: 32% of the obese patients died compared with 16% of those at lower weights.

One thing that puzzled the USC physicians who conducted the study was that the obese patients were less likely to suffer head injuries -- which killed the most people in both groups. About 72% of the thinner patients’ deaths were caused by brain injuries, compared with 60% of the obese patients’ deaths. Yet the obese patients were twice as likely as their counterparts to suffer acute respiratory distress syndrome, sepsis, or renal or multiple organ failure, or to die from multiple organ failure.

But complications were equally likely in both groups. And both the obese and non- obese survivors stayed about the same number of days in the hospital for their injuries, which were mostly sustained in traffic accidents. So it isn’t clear why the obese patients fared worse, said Dr. Carlos Brown, one of the four USC physicians who, along with one medical student, reported their results in the September issue of the Archives of Surgery.

Previous studies have offered conflicting results about whether obese patients have worse outcomes after traumatic injuries. One study found that preexisting medical conditions, but not obesity, increased trauma mortality, particularly in those with diabetes and heart disease.

The USC study did not assess so-called “co-morbid conditions” that obesity contributes to, including diabetes, high blood pressure and heart disease. Of the 242 patients studied, 63 (26%) were obese. Forty-nine patients died.

Brown speculated that obese patients’ bodies might trigger a worse “inflammatory response” to injury.

The article reporting the study results also raised the possibility that leptin, a hormone produced in quantity by obese people, somehow hinders the immune system.

“The fact that their high leptin levels do not correlate with the expected feedback response [to decrease food intake and increase energy expenditure] suggests that obese persons may be resistant to leptin,” the article said. “Could it be possible that leptin resistance in the obese population makes them more prone to inflammatory complications?”

A new, five-year study is underway.