(HealthDay News) —Obese children hospitalized for certain serious illnesses may have a higher risk of dying than thinner patients, a new research review suggests.
Experts caution that the findings are just "suggestive" of a link, and do not prove that critically ill children are more likely to die if they're obese.
But the results, published online March 11 in JAMA Pediatrics, add to the list of potential risks tied to childhood obesity.
Past studies have found that obese children face higher rates of some long-term health problems, such as type 2 diabetes, high blood pressure and asthma. They also tend to become obese adults, with all the potential health consequences that come with that, including increased risks of heart disease and certain cancers.
"This (study) suggests there may be more to childhood obesity than the risks we already know of," said lead researcher Lori Bechard, a clinical nutrition specialist at Boston Children's Hospital. "There may also be some near-term risks."
Bechard stressed, however, that the studies in her team's review had a number of limitations. They also varied widely in how they were done, and even in how they defined obesity.
"We don't feel confident that we can say there is an association" between obesity and seriously ill children's risk of dying, Bechard said. "We need more research."
Given that roughly 17 percent of U.S. children and teens are obese, this possible connection, if proven, could have significant implications.
The findings are based on data from 28 past studies of children ages 2 to 18 who were hospitalized for various reasons. Twenty-one studies looked at kids' risk of dying, and half of them found that for children with serious illnesses, obesity was linked to an increased risk of death.
The studies that did find a link tended to be larger and better done than the others. Still, Bechard said, "the evidence wasn't overwhelmingly consistent."
Besides the higher death risk in some reports, a couple of studies also found that obese children generally had a longer hospital stay. No clear link was established between obesity and the risk of contracting an infection in the hospital.
It's hard to know what to make of the results, said Dr. Patricia Vuguin, a pediatric endocrinologist at Cohen Children's Medical Center in New Hyde Park, N.Y.
"This is suggestive that there might be a relationship between obesity and higher mortality. But that doesn't tell us anything about causality," said Vuguin, who was not involved in the research.
The better-done studies tried to account for other factors—such as the severity of a child's disease—but there could be other reasons that obese children tended to be at greater risk of dying.
Thankfully, children rarely develop life-threatening illnesses, Vuguin said. "It's not common," she stressed. "It's unusual."
The review found no evidence that obese kids who were presumably in better health—those having elective surgery—had a higher-than-normal death risk. But it is so rare for children to die from elective surgery, Bechard said, it would be "very hard" for a study to detect a link with obesity, if there is one.
Vuguin said a big limitation is that nearly all studies on this issue have been retrospective, which means the researchers looked back in time at patient records. And those records may lack a lot of important information.
Bechard agreed. Prospective studies—where researchers enroll kids when they enter the hospital, then follow them over time—would give stronger evidence. "It would be helpful to do prospective studies, and have clearer definitions of obesity," Bechard said.
According to Vuguin, it's plausible that obesity could have some effect on how seriously ill children fare. It's thought that obesity creates a state of chronic, low-level inflammation in the body. And based on animal research, it's believed that can impair immune system function.
But it's not possible to tell from the current findings whether that explains the higher death risk seen in some obese children.
So for now, Bechard said, there are no practical implications from the results—only more questions. "We need to keep looking at the effects of being obese in childhood," she said.
Explore further: Childhood obesity -- what are the health risks?
For information on helping overweight kids, visit the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.