New Studies Highlight Increasing Prevalence of NAFLD/NASH

Editor's Note: Several related themes with high relevance to the prevalence, risk factors, outcomes, and treatment of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) emerged at The Liver Meeting®, the 2016 Annual Meeting of the American Association for the Study of Liver Diseases. What follows is an overview of some of those studies that seemed particularly important to advancing our understanding of these debilitating conditions.

Prevalence of NAFLD/NASH

In parallel with the obesity epidemic, the prevalence of fatty liver in all age groups has increased since the late 1980s to become one of the most common causes of chronic liver disease. An emerging concern is the apparent onset of significant NASH in early life, thereby planting the roots of chronic disease. Two presentations at The Liver Meeting emphasized this issue.

The prevalence of aggressive forms of NASH and advanced fibrosis in adolescents was estimated by Selvakumar and colleagues,^[1] who examined data from 8539 participants enrolled in the National Health and Nutrition Examination Survey (NHANES) in three time periods. NASH could not be diagnosed specifically, given the absence of a liver biopsy, so the investigators relied on a noninvasive predictive model based on readily available validated measures (cholesterol, total bilirubin, and waist circumference). The investigators found a significant, stepwise increase in the prevalence of both NAFLD and NASH from 3.3% and 0.74%, respectively, in the 1988-1994 period, to 8.8% and 3.1% in 1999-2004 and 10.1% and 3.4% in 2005-2010. Increasing trends in the prevalence of NASH were observed among all ethnic subgroups and both sexes. On multivariable analysis, older age, male gender, ethnicity (Mexican American), and body mass index (BMI) percentile were found to be associated with the highest odds of having NASH. The prevalence of NASH in the 2005-2010 period was highest among Mexican American adolescents (15.4%). As expected, the prevalence of advanced fibrosis was low in this age group (0.20% in the later period), with the highest prevalence noted in Mexican American adolescents (1.4%).

Alqahtani and colleagues^[2] estimated the increasing prevalence of NASH in obese children and adolescents in a prospective study, which included an assessment of liver biopsy samples obtained from 296 participants who underwent laparoscopic sleeve gastrectomy for morbid obesity. They found that 56% had NASH, 37% had clinically significant fibrosis, and 87% had portal inflammation. They also identified noninvasive measures of significant disease, including serum levels of high-density lipoproteins (HDL), triglycerides, glycated hemoglobin (A1c), and alanine aminotransaminase (ALT), and found that systolic and diastolic blood pressure levels were predictive of fibrosis, and that HDL, A1c, alkaline phosphatase, ALT, and aspartate aminotransaminase (AST) levels were predictive of NASH.

The data from these two studies serve as a wake-up call to the depth and potential impact of the increasing public health burden associated with early-onset NAFLD/NASH. This should be a strong signal to clinicians to enhance their efforts to prevent obesity, to screen for fatty liver in young persons, especially among high-risk populations, and to recommend healthy diet habits and weight loss. These efforts will hopefully interrupt the cascade of obesity-related disease and prevent progression of fatty liver disease.

Screening for NAFLD is now recommended for all obese or overweight children with additional risk factors, according to recently released clinical practice guidelines developed by the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition^[3] and endorsed by the American Academy of Pediatrics. These guidelines also outline recommendations for diagnosis, treatment, and follow-up care of children and adolescents with NAFLD.

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