It is difficult to obtain an accurate estimate of NASH prevalence given the fact that NASH is a silent disease, and a disease that remains difficult to diagnose for the time being, even though promising programs are currently in development. But the trends are clear: non-alcoholic fatty liver disease (NAFLD) is growing to become the most common chronic liver condition in Western populations in relation to the obesity and type 2 diabetes epidemics, and the prevalence of NASH is also expected to increase by 63% between 2015 and 2030 (Estes 2018). In the United States, NASH is expected to become the leading cause of liver transplantation by 2020.
Prevalence in the general population
NAFLD (NON-ALCOHOLIC FATTY LIVER DISEASE)
34%
NASH (NON-ALCOHOLIC STEATOHEPATITIS)
12%
NAFLD prevalence in the general population has been estimated in several studies using different methodologies. One study based on one of the largest database in the United-States (12.317 individuals) concluded that 34% of the general population of the United States were affected by NAFLD (Kim 2013), amounting to at least 42 millions of adults. In another meta-analysis study (Younossi 2017), worldwide prevalence of NAFLD was estimated at 25.2%.
The overall NASH prevalence in the adult population of developed countries has been estimated as high as 12% (Williams, 2011), with a heterogeneous repartition in relation to ethnicity:
- Hispanics: 19%
- Afro-Americans: 14%
- Caucasians: 10%
- Others: 7%
Populations at risk: prevalence in population with obesity
NAFLD is highly prevalent in populations suffering from obesity, but exact figures remain hard to estimate; in a study based on a population with severe obesity (BMI > 40), more than 90% of individuals had NAFLD (AASLD Practice Guideline, 2012). As for NASH prevalence, a study aggregating data from more than 1.600 individuals who had bariatric surgery revealed a prevalence of 37% (Machado, 2006).
Obesity trends: Growing to epidemic proportions over the last 30 years, obesity is expected to continue to keep increasing over the next decades, albeit at reduced pace. According to OECD, 47% of adult population in the United States will suffer from obesity by 2030, compared to 37.7% in 2014. This represents a 25% increase in obesity by 2030.
Populations at risk: prevalence in people with type 2 diabetes
NAFLD prevalence in populations with type 2 diabetes is estimated at approximately 70% in several studies; this estimation is also used in the AASLD Practice Guidelines. Depending on the methodologies and populations used in the respective studies, estimations of NASH prevalence in this population range from 22% to 70% (Williams et al. 2011 and Bazick et al. 2015).
Type 2 diabetes trends: worldwide diabetes rates are expected to grow by about 55% by the year 2035 according to the International Diabetes Federation, which means that this population at risk of NAFLD/NASH will increase dramatically over the next decades.
Pediatric NAFLD and NASH
Non-alcoholic fatty liver disease in children is a major health concern for the medical community. The phenomenon was first reported in 1983 and has since become a leading cause of childhood chronic liver disease which has also been fueled by the growing childhood obesity epidemic.
Several studies have found that approximately 10% of the pedatric population had NAFLD, with a higher incidence in children of hispanic origin (Schwimmer JB et al, 2006). For example, a study conducted in the United States in more than 8.500 individuals estimated that 10% and 3% of US adolescents were affected respectively by NAFLD and NASH (Selvakumar, Pediatric Clinics of North America 2017).
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References
Aguiree, F. et al., IDF Diabetes Atlas : sixth edition 2013 International Diabetes Federation
Bazick, J. et al., Clinical Model for NASH and Advanced Fibrosis in Adult Patients With Diabetes and NAFLD: Guidelines for Referral in NAFLD. Diabetes Care, 2015. 38(7): p. 1347-55.
Chalasani, N. et al., The diagnosis and management of non-alcoholic fatty liver disease: practice Guideline by the American Association for the Study of Liver Diseases, American College of Gastroenterology, and the American Gastroenterological Association. Hepatology, 2012. 55(6): p. 2005-23.
Estes, C. et al., Modeling the epidemic of nonalcoholic fatty liver disease demonstrates an exponential increase in burden of disease. Hepatology, 2018. 67(1): p. 123-133.
Kim, D. et al., Association between noninvasive fibrosis markers and mortality among adults with nonalcoholic fatty liver disease in the United States. Hepatology, 2013. 57(4): p. 1357-65.
Machado, M. et al., Hepatic histology in obese patients undergoing bariatric surgery. J Hepatol, 2006. 45(4): p. 600-6.
OECE, Obesity Update 2017. [online] https://www.oecd.org/els/health-systems/Obesity-Update-2017.pdf
Schwimmer, J.B. et al., Prevalence of fatty liver in children and adolescents. Pediatrics, 2006. 118(4): p. 1388-93.
Selvakumar, P.K. et al., Nonalcoholic Fatty Liver Disease in Children Hepatic and Extrahepatic Complications. Pediatr Clin N Am, 2017. 64 (2017) 659-675. Williams, C.D. et al., Prevalence of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis among a largely middle-aged population utilizing ultrasound and liver biopsy: a prospective study. Gastroenterology, 2011. 140(1): p. 124-31.
Younossi, Z.M. et al., Global epidemiology of nonalcoholic fatty liver disease-Meta-analytic assessment of prevalence, incidence, and outcomes. Hepatology, 2016. 64(1): p. 73-84.
