Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Dec 21, 2017; 23(47): 8263-8276
Published online Dec 21, 2017. doi: 10.3748/wjg.v23.i47.8263
Clinical epidemiology and disease burden of nonalcoholic fatty liver disease
Brandon J Perumpail, Muhammad Ali Khan, Eric R Yoo, George Cholankeril, Donghee Kim, Aijaz Ahmed
Brandon J Perumpail, Department of Medicine, College of Medicine, Drexel University, Philadelphia, PA 19129, United States
Muhammad Ali Khan, Division of Gastroenterology and Hepatology, Health Science Center, University of Tennessee, Memphis, TN 38163, United States
Eric R Yoo, Department of Medicine, Santa Clara Valley Medical Center, San Jose, CA 95128, United States
George Cholankeril, Donghee Kim, Aijaz Ahmed, Division of Gastroenterology and Hepatology, Stanford University School of Medicine, Palo Alto, CA 94304, United States
Author contributions: Perumpail BJ, Khan MA, Kim D, Cholankeril G and Ahmed A drafted the manuscript; Cholankeril G and Ahmed A critically revised intellectual input; all authors approved the final manuscript.
Conflict-of-interest statement: All authors have no conflicts of interest or financial disclosure relevant to this manuscript.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Aijaz Ahmed, MD, Associate Professor, Attending Doctor, Division of Gastroenterology and Hepatology, Stanford University School of Medicine, 750 Welch Road # 210, Palo Alto, CA 94304, United States.
Telephone: +1-650-4986091 Fax: +1-650-4985692
Received: October 22, 2017
Peer-review started: October 25, 2017
First decision: November 8, 2017
Revised: November 8, 2017
Accepted: December 4, 2017
Article in press: December 4, 2017
Published online: December 21, 2017

Nonalcoholic fatty liver disease (NAFLD) is defined as the presence of hepatic fat accumulation after the exclusion of other causes of hepatic steatosis, including other causes of liver disease, excessive alcohol consumption, and other conditions that may lead to hepatic steatosis. NAFLD encompasses a broad clinical spectrum ranging from nonalcoholic fatty liver to nonalcoholic steatohepatitis (NASH), advanced fibrosis, cirrhosis, and finally hepatocellular carcinoma (HCC). NAFLD is the most common liver disease in the world and NASH may soon become the most common indication for liver transplantation. Ongoing persistence of obesity with increasing rate of diabetes will increase the prevalence of NAFLD, and as this population ages, many will develop cirrhosis and end-stage liver disease. There has been a general increase in the prevalence of NAFLD, with Asia leading the rise, yet the United States is following closely behind with a rising prevalence from 15% in 2005 to 25% within 5 years. NAFLD is commonly associated with metabolic comorbidities, including obesity, type II diabetes, dyslipidemia, and metabolic syndrome. Our understanding of the pathophysiology of NAFLD is constantly evolving. Based on NAFLD subtypes, it has the potential to progress into advanced fibrosis, end-stage liver disease and HCC. The increasing prevalence of NAFLD with advanced fibrosis, is concerning because patients appear to experience higher liver-related and non-liver-related mortality than the general population. The increased morbidity and mortality, healthcare costs and declining health related quality of life associated with NAFLD makes it a formidable disease, and one that requires more in-depth analysis.

Keywords: Nonalcoholic fatty liver disease, Hepatic steatosis, Fatty liver, Prevalence, Incidence, Fibrosis, Risk factor, Epidemiology, Outcomes, Nonalcoholic steatohepatitis

Core tip: Nonalcoholic fatty liver disease (NAFLD) is a term for a host of histological findings stemming from hepatic steatosis and remains the most common liver disease globally with increasing prevalence. The vast variation in disease presentation complicates diagnosis, leading to an underestimate of actual disease occurrence. NAFLD is associated with many metabolic comorbidities, including obesity, type II diabetes, dyslipidemia, and metabolic syndrome. Its potential to develop into more severe liver conditions, such as nonalcoholic steatohepatitis, advanced fibrosis, cirrhosis and hepatocellular carcinoma, can lead to a state in which liver transplantation is the only treatment option available. The population at risk of developing progressive liver disease creates a challenge to the healthcare system in terms of screening for this evolving epidemic of liver disease.