In people who have non-alcoholic fatty liver disease (NAFLD) a build-up of fat cells in the liver may have a higher risk of dementia, according to a new study.

NAFLD is the most common liver disease, affecting approximately 25 per cent of the world's population. Being largely asymptomatic, the disease may progress from the accumulation of fat in liver cells to liver inflammation and liver cirrhosis.

While excessive alcohol use can cause fatty liver, NAFLD can be caused by obesity and related conditions like high blood pressure or Type 2 diabetes.

The study, published in the journal Neurology, showed that people with NAFLD who also have heart disease or who have had a stroke may have an even higher risk of dementia. When compared to people without liver disease, people with NAFLD had a 38 per cent higher rate of dementia overall.

When looking specifically at vascular dementia caused by inadequate blood flow to the brain, researchers found people with NAFLD had a 44 per cent higher rate than people without liver disease. Researchers did not find a higher rate of Alzheimer's disease.

People with liver disease who also had heart disease had a 50 per cent greater risk of dementia. Those who had liver disease and stroke had more than a 2.5 times greater risk of dementia.

"Our study shows that non-alcoholic fatty liver disease is associated with the development of dementia, which may be driven mainly by vascular damage in the brain," said Ying Shang from the Karolinska Institute in Sweden.

"These results highlight the possibility that targeted treatment of this form of liver disease and co-occurring cardiovascular disease may reduce the risk of dementia."

For the study, researchers identified 2,898 people aged 65 and older who were diagnosed with NAFLD. Researchers then identified 28,357 people without the disease who were matched for age, sex and city of residence at age of diagnosis.

After an average of more than five years of follow-up, 145 people with NAFLD, or 5 per cent, were diagnosed with dementia, compared to 1,291 people without liver disease, or 4.6 per cent.