Since the late 1980s, the prevalence of non-alcoholic fatty liver disease (NAFLD) among US adolescents has more than doubled, a new study suggests.
"Preventing children from becoming overweight will prevent most NAFLD," Dr Miriam Benedecta Vos from Emory University School of Medicine, Atlanta, Georgia said. "Prevention will involve teaching and supporting parents of young children to avoid sugar sweetened drinks, to limit TV/screen time to one hour per day, to serve 1/2 plate vegetables, and to ensure at least 60 minutes physical activity per day."
Dr Vos and colleagues used data from several National Health Examination Surveys (NHANES) for 12 to 19 year olds to track the NAFLD prevalence rates from 1988-1994 to 2007-2010 and to determine whether those rates have gone up in line with increases in obesity prevalence.
As reported online in The Journal of Pediatrics, they defined suspected NAFLD as elevated ALT in an overweight or obese child.
How the research was done
Using the recently defined sex-specific cut points for elevated ALT of >25.8 U/L for boys and >22.1 U/L for girls, the prevalence of suspected NAFLD increased from 3.9% in 1988-1994 to 10.7% in 2007-2010.
In stratified analyses, there were increasing trends in suspected NAFLD prevalence among all race/ethnic subgroups, among both males and females, and among those who were obese. The observed increase among overweight children was not significant.
Mexican Americans had the highest prevalence, and non-Hispanic blacks had the lowest prevalence. Suspected NAFLD prevalence was two to three times higher among males than among females.
More than a quarter of obese females (27.0%) and nearly half of obese males (48.3%) had suspected NAFLD in the latest survey.
"Although the increasing prevalence of obesity and severe obesity over the study period is a likely explanation for some of the observed increase in suspected NAFLD," the researchers note, "the findings of this study highlight the importance of other factors."
Persuade food industry
Factors independently associated with increased NAFLD risk included increased age, increased body-mass index z-score, Mexican American ethnicity, and being male.
"Previous research suggests an association between diet, specifically increased consumption of sugar sweetened beverages, and NAFLD risk," the investigators add.
"We are part of an NIH sponsored research network that is following children with NAFLD over time," Dr Vos said. "These studies include tracking the liver findings as well as the cardiovascular disease risk as they age into young adults."
Dr Vos stressed the importance of screening because of the high prevalence of NAFLD, particularly among obese adolescents.
Dr Valerio Nobili from Bambino Gesu Children's Hospital, Rome, Italy said that more than a million children in Italy alone now have NAFLD. "We must take preventive health policies if we want to avoid that this generation of teens will have a life expectancy less than that which preceded it," Dr Nobili said.
He added that this study "is important because it emphasises once again how strategically important it is to diagnose this disease before its progressive form reaches such an advanced state to render unnecessary any treatment other than liver transplantation."
"The most important step and, unfortunately, the most difficult, too, should be to persuade the food industry in packaging foods more healthy and less processed chemically reducing the profit margin for the benefit of quality," Dr Nobili concluded.
(Reuters Health, November 2012)
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