Nonalcoholic steatohepatitis (NASH) is a type of nonalcoholic fatty liver disease (NAFLD). Fatty liver disease is when fat makes up more than 5% of the liver’s weight. The 2 main types of fatty liver disease are called alcoholic liver disease (ALD) and NAFLD. Alcoholic liver disease is caused by heavy alcohol use, while in NAFLD, the buildup of liver fat is not caused by drinking too much alcohol.
NAFLD is one of the most common causes of liver disease in the world. In people with NASH, the buildup of fat in the liver causes inflammation of the liver (hepatitis) and liver cell damage. This inflammation and cell damage can cause scarring (fibrosis) of the liver and lead to the liver not working as well as it should. NASH may also lead to cirrhosis (a late stage of scarring, which can eventually cause liver failure) or, in some cases, liver cancer.
The exact cause of NASH is not known. However, there is an increased risk of developing NASH associated with obesity, insulin resistance and type 2 diabetes, high cholesterol and high triglycerides (fat-like substances in the blood), and metabolic syndrome. Metabolic syndrome is a group of risk factors, including high blood pressure, high blood sugar, excess abdominal fat, and unhealthy cholesterol or triglyceride levels, that when combined can lead to heart disease, stroke, and diabetes.
People who develop NASH are usually middle-aged, and have at least one of the risk factors above. However, NASH can also develop in people of any age who do not have any of these problems.
In the United States, 30% to 40% of adults have NAFLD and 3% to 12% of adults have NASH. Globally, it is estimated that approximately 20% of people with NAFLD have NASH.
In the early stages of NASH, people will often not experience any symptoms. Most people feel normal and are not aware that they have the condition. However, after several years of damage to the liver, people may start to experience the following symptoms:
There are opportunities for people with NASH and healthy volunteers to contribute to NASH clinical research, and potentially change the future treatment of this life-limiting condition.
The resources below provide further information on NASH and advice on taking part in clinical research.