Prevalence of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis is increasing and early detection is critical. Brush up on basics with our slides.
Clinicians in primary care, diabetes, and obesity settings should have a high index of suspicion for nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), according to the American Association for the Study of Liver Diseases (AASLD). NAFLD prevalence has increased in lock-step with the obesity pandemic and one- to two-thirds of patients with type 2 diabetes have the disorder.
A data‐supported approach to the diagnosis, treatment, and prevention of NAFLD is provided in a guidance document from the AASLD published in Hepatology. For a brief summary of the basic NAFLD/NASH facts and figures, click through the slides below.
NAFLD defined. In the document’s definition of NAFLD, there must be evidence of hepatic steatosis (HS) by imaging or histology and a lack of secondary causes of hepatic fat accumulation (eg, significant alcohol consumption). There is an association with metabolic comorbidities (eg, obesity, type 2 diabetes mellitus [T2DM]), and dyslipidemia) in most patients.
NAFLD categorized. NAFLD may be categorized as nonalcoholic fatty liver (≥5% HS without evidence of hepatocellular injury in the form of hepatocyte ballooning) or NASH (≥5% HS and inflammation with hepatocyte injury, possibly with fibrosis).
NAFLD incidence and prevalence. The estimated incidence of NAFLD varies from ~28 per 1000 person‐years in Western countries to ~52 per 1000 person‐years in Asia. The overall global prevalence of NAFLD diagnosed by imaging has been estimated at ~25.24%. The highest prevalence is reported in the Middle East and South America and the lowest in Africa. There has been no direct assessment of the incidence or prevalence of NASH, but prevalence in the general population may range between 1.5% and 6.45%.
Obesity tops NAFLD risk factors. A bidirectional association between NAFLD and metabolic syndrome (MetS) is well established—MetS features are highly prevalent in patients with NAFLD, and MetS components increase NAFLD risk. Of the established metabolic comorbidities, obesity is the most common and well‐documented risk factor. More than 95% of patients with severe obesity who undergo bariatric surgery will have NAFLD. Other conditions associated with NAFLD include sleep apnea, colorectal cancer, osteoporosis, psoriasis, endocrinopathies, and polycystic ovary syndrome independent of obesity.
Bidirectional causal relationship with diabetes confounds prevalence. The prevalence of NAFLD in patients with T2DM is known to be very high—an estimated one-third to two-thirds of patients with T2DM have NAFLD. However, the potential simultaneous development of T2DM and NAFLD in a patient may confound the prevalence of NAFLD in patients with T2DM and the prevalence of T2DM in patients with NAFLD.
Dyslipidemia and other risk factors. Patients with NAFLD frequently have high serum triglyceride levels and low serum high‐density lipoprotein levels. Prevalence of NAFLD in persons with dyslipidemia who attend lipid clinics was estimated at 50%. NAFLD prevalence and stage of liver disease appear to increase with age. Male sex has been considered a risk factor. Ethnic differences reported for NAFLD may be explained by genetic variation related to the patatin‐like phospholipase domain‐containing protein 3 gene.
NAFLD adverse outcomes and death. Patients with histologic NASH, especially those with some degree of fibrosis, may be at higher risk for cirrhosis, liver‐related mortality, and other adverse outcomes. Cardiovascular disease is the most common cause of death in patients with NAFLD. Liver‐related mortality, the 12th leading cause of death in the general population, is the second or third leading cause among patients with NAFLD. Cancer‐related mortality is a leading cause of death.
Rise in liver cancer. Concurrent with the obesity epidemic, NAFLD‐related hepatocellular carcinoma (HCC) was shown to increase in incidence at a 9% annual rate. Now NAFLD may be the third‐most common cause of HCC in the United States. Compared with other patients with HCC, those with NAFLD‐related HCC are older, have a shorter survival time, have more heart disease, and more likely will die from their primary liver cancer. Some patients who have HCC with NAFLD may not have cirrhosis.
Fibrosis and liver transplantation. Hepatic fibrosis (HF) is the most important histologic feature of NAFLD associated with long‐term mortality. HF progression in patients with histologic NASH at baseline showed a mean annual fibrosis progression rate of 0.09 in a meta‐analysis. An international study of patients who had NAFLD with advanced fibrosis showed an overall 10‐year survival of 81.5%, a rate similar to that of matched patients with HCC.