May 18, 2012 -- Nearly 10 percent of U.S. teens have nonalcoholic fatty liver disease, a largely silent accumulation of fat in their liver cells that puts them at risk for developing later cardiovascular disease and additional liver problems, new research has found.
Most of the increase in cases of NAFLD (disease not brought on by alcohol-related liver damage) is occurring among the heaviest teens -- those considered obese, based on their height, weight and age, said lead researcher Dr. Miriam Vos, a pediatric gastroenterologist at Emory University in Atlanta.
"We tried to see where the increase was happening and it looks like it's happening in the obese group," she said.
But ill health is not inevitable for obese teens whose livers already have sustained damage, said Vos, an assistant professor of pediatrics. "We think that liver disease is reversible, particularly for a teenager if they can make substantial changes and improve their weight," she added.
Vos determined that the prevalence of fatty liver among U.S. teens has more than doubled in the past two decades, from 3.6 percent to 9.9 percent, outpacing the rise in teenage obesity during that time and suggesting obesity is only a partial explanation for a rise. Vos' findings come from health data collected for 10,359 adolescents who participated in the National Health and Examination Survey (NHANES) between 1988 and 2008.
Even without fully understanding why numbers are up, "this is a disease that definitely needs attention. We need programs that focus on prevention of both obesity and fatty liver disease," said Vos, who is scheduled to present her findings Monday at Digestive Disease Week in San Diego, an annual gathering of nearly 16,000 physicians, researchers and academics.
The increase in fatty liver and its associated risks provide strong support for "recommendations to screen for NAFLD in obese adolescents," Vos and her colleagues concluded.
"Fatty liver disease kind of goes with the whole obesity epidemic," said Dr. Joseph A. Skelton, a pediatric gastroenterologist and associate director of the Center for Family Obesity Research at Wake Forest University School of Medicine in Winston-Salem, N.C., who was not involved in Vos' research.
He said that getting youngsters to eat healthier, be more active and maintain a healthy weight is "going to have the biggest impact, because there aren't any good drug treatments for fatty liver disease."
Vos said the researchers undertook the study to see whether there was evidence for a perception among GI specialists that they were seeing more cases of fatty liver disease in young patients. "Doctors are also looking for it more often, so it was difficult to tell if there were more cases because they were looking more often, or because there actually were more cases," she said.
In her own pediatric gastroenterology practice, Vos commonly sees "multiple cases per week" and because of the volume of cases, now runs a clinic for youngsters with fatty liver. Although the NHANES data only looked at youngsters 12 and older, Vos said fatty liver disease can develop well before that. "We certainly see 7-, 8- and 9-year-olds with it," she said.
Vos calculated the prevalence of teens with probable liver disease by identifying those youngsters who met the statistical definition of being overweight (in the 85th to 95th percentile for body mass index for their age) or obese (above the 95th percentile for BMI) who also had elevated levels of an enzyme called alanine aminotransferase (ALT) in their blood.
When the liver is damaged or diseased, it releases more ALT into the bloodstream. The method "is not perfect," she said, but it's the most sensitive way to get at the information short of doing an invasive liver biopsy, which wouldn't be ethically feasible.