Two people regularly have a few alcoholic drinks daily. One develops liver disease. The other doesn't.
What explains the different outcomes?
The answer may lie in a condition known as metabolic syndrome, a cluster of conditions that together raise the risk of coronary heart disease, diabetes, stroke and other serious health problems. This syndrome, characterized by symptoms such as abdominal fat, high blood pressure, high cholesterol and high blood sugar, affects more than one in three Americans.
A new study from Keck Medicine of USC published in the Annals of Internal Medicine shows that heavy alcohol use may be dramatically more damaging to the liver for people with metabolic syndrome.
Our research suggests that metabolic syndrome and alcohol interact in such a way that they multiply the effect of alcohol on the liver, more than doubling the risk of advanced liver disease among heavy drinkers. Drinking is harmful to the liver, but especially so for this segment of the population."
Brian P. Lee, MD, MAS, hepatologist and liver transplant specialist with Keck Medicine, lead author on the study
In the study, heavy alcohol use was defined as two drinks (a total of 12 fluid ounces) a day for women and three drinks (a total of 18 fluid ounces) per day for men.
Lee and his colleagues were motivated to research a connection between advanced liver disease, alcohol use and metabolic syndrome after noticing that between 2009-2018, deaths from alcohol-associated liver disease surged in the United States by more than 30% while alcohol use, including heavy drinking, remained stable or declined.
During the last 20 years, the number of Americans with metabolic syndrome increased significantly. Previous research has shown that metabolic syndrome can cause liver abnormalities.
"We therefore hypothesized that metabolic syndrome could be an important contributor to this unexplained surge in advanced liver disease," said Lee.
For the study, Lee and his fellow researchers used data from the National Health and Nutrition Examination Survey, which assesses the health and nutritional status of adults and children in the United States, pulling together samples representing the U.S. population 20 years or older between 1999 and 2018.
While the data revealed a slight increase in advanced liver disease with heavy alcohol use without metabolic syndrome, the greatest increase in advanced liver disease was found in those with combined heavy alcohol use and metabolic syndrome.
Lee believes that the increased risk of liver damage from drinking is a result of an increase in the amount of fat in the liver. A healthy liver contains less than five percent fat; any more than that can lead to inflammation and cirrhosis (scarring) of the liver, liver cancer and liver failure.
"Both metabolic syndrome and drinking increase liver fat, and we think that the combination of the two accelerates the accumulation of fat in the liver and fuels inflammation, resulting in a greater chance of liver disease," said Lee.
He hopes the study will encourage physicians who screen and diagnose patients with metabolic syndrome to also ask about alcohol use and look for liver disease.
"Our study indicates that these conditions may often coexist, and it is in patients' best interest to address both issues," he said. "It's also important for people with metabolic syndrome to realize they may be at an increased likelihood of advanced liver disease, and to monitor their drinking accordingly," he added.
The other authors of the study are Jennifer Dodge, MPH, assistant professor of research medicine and population and public health sciences with the Keck School of Medicine of USC; Wendy Mack, PhD, professor of population and public health sciences with the Keck School of Medicine; Adam Leventhal, PhD, professor of population and public health sciences with the Keck School of Medicine and director of the USC Institute for Addiction Science and Norah Terrault, MD, MPH, a Keck Medicine gastroenterologist and division chief of gastroenterology and liver diseases with the Keck School of Medicine.
Lee, B. P., et al. (2023). National Trends in Alcohol Use, Metabolic Syndrome, and Liver Disease From 1999 to 2018. Annals of Internal Medicine. doi.org/10.7326/m23-0518.