(Reuters Health) - Fatty liver disease that is not related to excess drinking is associated with greater brain shrinkage than normally happens with age, researchers say.

The reduced brain volume linked to non-alcoholic fatty liver disease (NAFLD) is equivalent to an extra 4.2 years of aging for people in their 60s and early 70s, researchers report in JAMA Neurology, or an extra 7.3 years of aging for people under age 60.

“Liver fat may have a direct association with brain aging,” lead author Galit Weinstein from School of Public Health at the University of Haifa in Israel said in an email.

Recent studies have shown that people with NAFLD have impaired thinking and decreased brain activity compared with others, the authors note. To figure out why, they used MRI scans to measure the overall brain volume of 766 middle-aged men and women and used abdominal CT scans to examine their livers. About 18 percent of the participants had fatty liver disease.

The researchers accounted for risk factors for brain aging, including blood fat levels, heart disease, diabetes, smoking, alcohol consumption, overweight, lack of exercise and menopausal status.

People with NAFLD had more harmful risk factors than people without fatty liver disease, but even after adjusting for these risks, NAFLD was associated with significantly smaller total brain size. Even in people 75 and older, it was the equivalent of an extra 1.5 years of brain aging compared to peers without fatty liver disease.

NAFLD didn’t seem to be associated with other signs of brain injury or stroke, the researchers note.

NAFLD can be improved by lifestyle modifications, such as healthy eating and increased physical activity, Weinstein told Reuters Health.

“This is extremely important when it comes to brain health, because currently there is usually no cure for neurodegenerative diseases, such as Alzheimer’s disease. But it still remains to show in other studies that improvement in fatty liver disease is associated with lower risk of such brain diseases,” she said.

“Fatty liver can be prevented by conducting appropriate lifestyle and diet,” Weinstein added. “In turn, if one retains a healthy liver, his/her risk for other diseases, such as diabetes and heart diseases, is also reduced. In this study, we show that keeping a healthy liver may also be linked with a healthier brain.”

SOURCE: bit.ly/2jM3dXt JAMA Neurology, online November 20, 2017.