Non-alcoholic fatty liver disease (NAFLD) has become a leading cause of advanced liver disease and related complications, and rates continue to rise worldwide, according to a pair of recent studies published in the Journal of Hepatology

Arising from the accumulation of fat in the liver, NAFLD and its more severe form, non-alcoholic steatohepatitis (NASH), are responsible for a growing proportion of advanced liver disease. As a result of inflammation, NAFLD can lead to liver fibrosis, cirrhosis and even liver cancer. With no effective approved medical therapies, disease management is dependent on lifestyle changes such as weight loss and exercise.

The cause of advanced liver disease, including liver cancer, is largely shifting away from hepatitis B (which can be prevented with a vaccine) and hepatitis C (which can be cured with antiviral therapy) toward NAFLD. For liver transplantation as well, NAFLD has become a leading indication.

In a systematic review and meta-analysis, Mindie Nguyen, MD, of Stanford University Medical Center, and colleagues assessed the global prevalence of NAFLD. The authors identified 63 relevant studies, mostly in Asia, that together included a total of 1,201,807 participants. Of this study population, 242,568 people developed NAFLD, for an incidence rate of 4,613 cases per 100,000 person-years.

Between 2000 and 2015, the incidence of NAFLD rose threefold. The prevalence was higher among men compared with women and among smokers versus nonsmokers. Further, people with overweight or obesity were three times more likely to develop NAFLD than those with normal weight.

“As treatment options for NAFLD remain limited, prevention of NAFLD should remain the focus of public health,” wrote the researchers. “Studies such as these can help policymakers in determining which and whether their prevention interventions are impactful.”

In another review of existing studies, Hannes Hagström, MD, PhD, of Karolinska University Hospital in Sweden, and colleagues also examined the epidemiology and trends in fatty liver disease.

Around the world, NAFLD has become the predominant type of liver disease. From 2016 to 2019, NAFLD prevalence grew to affect 38% of the world’s population. This is more than a 50% rise from the 25% prevalence between 1990 and 2006.

The increase in NAFLD parallels the global rise in the prevalence of diabetes and obesity. Genetic and socioeconomic factors contribute greatly to the wide geographical differences in NAFLD rates across countries.

Only a small proportion of people with fatty liver disease will go on to develop hepatocellular carcinoma (HCC), the most common type of primary liver cancer, or need a transplant. But as NAFLD prevalence grows, so will the absolute number of people with related conditions and complications. What’s more, NAFLD is now being diagnosed at younger ages, allowing more time for progression to severe liver disease. Cirrhosis rates are projected to double worldwide between 2016 and 2030, and liver-related deaths in the United States are expected to rise dramatically.

“Because chronic liver disease takes time to progress, any rise in the NAFLD prevalence will be paralleled by an increase in cirrhosis, cirrhotic complications and HCC one to two decades later,” wrote the study authors. “Despite regional differences, the health care burden is and will be tremendous, and the importance of prevention, case identification, clinical care pathways and effective treatments cannot be overemphasized.”

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