Systematic review: the epidemiology and natural history of non‐alcoholic fatty liver disease and non‐alcoholic steatohepatitis in adults

Abstract

Aliment Pharmacol Ther 2011; 34: 274–285 Summary Background Non‐alcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease, and its worldwide prevalence continues to increase with the growing obesity epidemic. This study assesses the epidemiology of NAFLD in adults based on clinical literature published over the past 30 years. Aim To review epidemiology and natural history of non‐alcoholic fatty liver disease and non‐alcoholic steatohepatitis in adults based on clinical literature published over the past 30 years. Methods An in‐depth search of PubMed (1980–2010) was based on five search terms: ‘non‐alcoholic fatty liver disease’ OR ‘non‐alcoholic steatohepatitis’ OR ‘fatty liver’ OR ‘steatosis’ AND ‘incidence’ [MeSH Terms] OR ‘prevalence’ [MeSH Terms] OR ‘natural history’. Studies of paediatric cohorts were excluded. Articles were categorised by topic and summarised, noting generalisations concerning their content. Results Four study categories included NAFLD incidence, prevalence, risk factors and natural history. Studies related to NAFLD prevalence and incidence indicate that the diagnosis is heterogeneous and relies on a variety of assessment tools, including liver biopsy, radiological tests such as ultrasonography, and blood testing such as liver enzymes. The prevalence of NAFLD is highest in populations with pre‐existing metabolic conditions such as obesity and type II diabetes. Many studies investigating the natural history of NAFLD verify the progression from NASH to advanced fibrosis and hepatocellular carcinoma. Conclusions Non‐alcoholic fatty liver disease is the most common cause of elevated liver enzymes. Within the NAFLD spectrum, only NASH progresses to cirrhosis and hepatocellular carcinoma. With the growing epidemic of obesity, the prevalence and impact of NAFLD continues to increase, making NASH potentially the most common cause of advanced liver disease in coming decades.

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

“…12,13 The reported prevalence of NAFLD when defined by liver ultrasound ranged between 17% and 46% depending on the population studied. 4 In a study consisting of nearly 400 middle aged individuals, the prevalence of NAFLD defined by ultrasonography was 46% and the prevalence of histologically confirmed NASH was 12.2%. 14 In the Dallas Heart Study, when assessed by MR spectroscopy the prevalence of NAFLD in the general population was 31%.…”

“…15 The prevalence of suspected NAFLD when estimated using aminotransferases alone without imaging or histology ranged between 7% and 11%, but aminotransferases can be normal in individuals with NAFLD. 4 In summary, estimates of the worldwide prevalence of NAFLD ranges from 6.3% to 33% with a median of 20% in the general population, based on a variety of assessment methods. 4 On the other hand, the estimated prevalence of NASH is lower, ranging from 3 to 5%.…”

“…4 In summary, estimates of the worldwide prevalence of NAFLD ranges from 6.3% to 33% with a median of 20% in the general population, based on a variety of assessment methods. 4 On the other hand, the estimated prevalence of NASH is lower, ranging from 3 to 5%. 4 The prevalence of NASH cirrhosis in the general population is not known.…”

“…4 On the other hand, the estimated prevalence of NASH is lower, ranging from 3 to 5%. 4 The prevalence of NASH cirrhosis in the general population is not known. (Table 4) Obesity is a common and well documented risk factor for NAFLD.…”

Hepatic iron concentration correlates with insulin sensitivity in nonalcoholic fatty liver disease

“…NAFLD is estimated to be present in 20%‐30% of the adult population 1. Nonalcoholic steatohepatitis, the aggressive form of NAFLD, predisposes individuals toward liver failure and hepatocellular carcinoma 2. Furthermore, NAFLD has been shown to be an independent risk factor for cardiovascular disease and type II diabetes 3…”