The Burden of NAFLD Worldwide
Nonalcoholic fatty liver disease (NAFLD) is now considered to be the fastest growing cause of chronic liver disease worldwide. Recent estimates suggest that 25% of the world have NAFLD. Although only a small proportion of NAFLD patients will progress to e
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The Burden of NAFLD Worldwide Zobair Younossi and Linda Henry
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Background
Nonalcoholic fatty liver disease (NAFLD) is rapidly becoming the most common cause of chronic liver disease and is now among the top causes of cirrhosis, hepatocellular carcinoma (HCC), and indications for liver transplantation in United States and probably the rest of the world [1, 2]. However, NAFLD is not a single disease but rather a spectrum of clinico-pathologic liver diseases that include nonalcoholic fatty liver (NAFL or simple steatosis), nonalcoholic steatohepatitis (NASH), cirrhosis, and its complications [3]. Furthermore, NAFLD is considered the hepatic manifestation of metabolic syndrome since most NAFLD patients have visceral adiposity, insulin resistance, and/or type 2 diabetes mellitus, hypertension, hypercholesteremia, and hypertriglycemia. In fact, the more components of metabolic syndrome are present in patients with NAFLD, the higher the risk of advanced fibrosis and liver-related mortality [1–4].
Z. Younossi (*) Center for Liver Diseases, Department of Medicine, Inova Fairfax Hospital, Falls Church, VA, USA Betty and Guy Beatty Center for Integrated Research, Inova Health System, Falls Church, VA, USA e-mail: [email protected] L. Henry Betty and Guy Beatty Center for Integrated Research, Inova Health System, Falls Church, VA, USA Center for Outcomes Research in Liver Diseases, Washington, DC, USA © Springer Nature Switzerland AG 2020 E. Bugianesi (ed.), Non-Alcoholic Fatty Liver Disease, https://doi.org/10.1007/978-3-319-95828-6_2
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Z. Younossi and L. Henry
Global and Regional Prevalence of NAFLD and NASH
Currently, 25% of the world is thought to have NAFLD with the highest prevalence being reported from the Middle East and South America (31.79% and 30.45%, respectively) and the lowest from Africa (13.48%) [4]. The prevalence of NAFLD in North America, Europe, and Asia has been reported as 24.13%, 23.71%, and 27.37%, respectively. Other histologic-based studies from Europe have suggested a NAFLD prevalence of approximately 20% while in Asia NAFLD prevalence is thought to range from 19 to 23% [3, 4]. Among patients with type 2 diabetes, the prevalence of NAFLD is higher at 57.80% [5]. Furthermore, among the morbidly obese, NAFLD prevalence has been found to be 95% [6]. Since diagnosis of NASH is based on histology, true prevalence rates for NASH in the general population is not known. On the other hand, estimated prevalence rates for NASH in the general population is considered to range from 1.5 to 6.45% [4]. In contrast, the prevalence of NASH in patients with type 2 diabetes is higher. A recent meta-analysis suggested that the overall prevalence of NASH among biopsied diabetics is 65.26% with 15.05% of these patients having advanced fibrosis (fibrosis ≥ F3) [5]. Finally, the prevalence of NAFLD among very obese individuals undergoing bariatric surgery is over 95%, while 20–50% of them have NASH and about 10% have advanced fibrosis [6]. As the rates of obesity, type 2 diabetes mellitus, a
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