(Reuters Health) - The only liver disease becoming more widespread in the U.S. is one driven by obesity and diabetes, even as other types of liver disorders linked to drinking or hepatitis are becoming less common, researchers say.

For the study, researchers examined nationwide health survey data collected in five cycles between 1988 and 2016. Over this period, the proportion of adults with what’s known as non-alcoholic fatty liver disease (NAFLD) rose from 20% to 28.3%, mirroring increases in rates of obesity and diabetes over the same period.

“Liver disease in the United States is experiencing a shift away from viral hepatitis to NAFLD,” said Dr. Zobair Younossi MD, lead author of the study and chair of the department of medicine at Enova Fairfax Hospital in Falls Church, Virginia.

“This is primarily driven by the epidemic of obesity and diabetes,” Younossi said by email. “This is important to patients because NAFLD can be a silent disease for decades.”

During the study period, the proportion of the population with obesity rose from 22.2% to 38.9% while the proportion with diabetes climbed from 7.2% to 13.5%, researchers report in Gut.

Alcoholic liver disease rates were little changed during the study period, affecting about 0.8% to 1% of the population.

The proportion of people with chronic viral hepatitis infections that can be spread through contact with blood became less common or remained stable.

Hepatitis B - spread through blood, semen and other bodily fluids - held steady, affecting about 0.3% to 0.4% of people throughout the study period.

And the prevalence of hepatitis C - which often spreads when injected drug users share needles - dropped from 1.6% to 0.9% over the study period.

It’s possible that hepatitis infections may have increased more recently with the rise in opioid abuse, but the study period didn’t capture this shift, the researchers note.

Many people may not realize they have NAFLD because they can live symptom-free for years, the study team writes. Researchers identified NAFLD cases based on ultrasound results showing liver damage in participants.

People in the study with NAFLD were more likely to be male, older and Hispanic.

Most people have a little bit of fat in their liver, but in fatty liver disease, more than 5% of the liver by weight is made up of fat. If the condition isn’t linked to liver damage from heavy drinking, it’s known as non-alcoholic fatty liver disease (NAFLD) and is most often associated with obesity, diabetes and certain eating habits.

In the study population, being obese raised the odds of having NAFLD more than 10-fold, and having diabetes raised the likelihood nearly four-fold, the analysis found.

Roughly four in five people with both obesity and type 2 diabetes had NAFLD.

The study wasn’t designed, however, to determine whether or how any individual characteristics might cause NAFLD.

“People with NAFLD and obesity should ask their doctors for support to lose weight, as even modest weight loss would improve NAFLD and they are more likely to succeed in their efforts with the appropriate support in place,” said Dimitrios Koutoukidis, a liver disease researcher at the University of Oxford in the UK who wasn’t involved in the study.

“Having a healthy diet and being physically active may also help improve NAFLD,” Koutoukidis added.

SOURCE: bit.ly/2H6Xvbv Gut, online July 31, 2019.