Epidemiology and Natural History of Nonalcoholic Fatty Liver Disease

The epidemic of obesity has resulted in a parallel incremental burden of nonalcoholic fatty liver disease (NAFLD) worldwide. Nonalcoholic fatty liver disease includes a spectrum of liver disease that ranges from simple fat accumulation in the liver to necroinflammation, fibrosis, cirrhosis, and hepatocellular carcinoma, which in essence represent the stages of the natural history of NAFLD. The rising prevalence of NAFLD globally may be accounted for by changes in dietary habits and an increase in sedentary lifestyle. Nonalcoholic steatohepatitis (NASH), the aggressive form of NAFLD, is currently the second leading etiology of liver disease among adults awaiting liver transplantation in the United States. In the current review, the authors discuss the uncertainty around the progression from NAFL (steatosis) to NASH (steatohepatitis), the undisputed progression of NASH to cirrhosis, and the risk factors that predispose to such progression. The published literature on the long-term cardiovascular complications and liver-related mortality of NAFLD is also discussed.