MONDAY, Nov. 28 (HealthDay News) -- A condition called non-alcoholic fatty liver disease (NAFLD) does not increase the risk of death, according to a new study finding that surprised Johns Hopkins researchers.

It's long been thought that NAFLD -- a condition associated with obesity and heart disease -- had a detrimental impact on health and longevity. But the new study concluded that NAFLD does not affect survival.

"Physicians have considered fatty liver disease a really worrisome risk factor for cardiovascular disease," study leader Dr. Mariana Lazo, a postdoctoral fellow at the Johns Hopkins University School of Medicine's Welch Center for Prevention, Epidemiology, and Clinical Research, said in a Hopkins news release.

"Our data analysis shows this doesn't appear to be the case. We were surprised to say the least because we expected to learn by how much non-alcoholic fatty liver disease increased the risk of death and instead found the answer was not at all," Lazo explained.

The researchers analyzed data from more than 11,000 Americans, aged 20 to 74, who were followed for up to 18 years as part of the Third National Health and Nutrition Examination Survey.

No evidence of increased risk of death was found among the 20 percent of participants with NAFLD, according to the study published Nov. 18 in BMJ.

According to the American Liver Foundation, NAFLD affects up to 25 percent of Americans. The condition is characterized by the liver's inability to break down fats, along with fat accumulation in the liver.

"We don't yet know why mortality is not affected or whether there might be some actual protective effect of non-alcoholic fatty liver disease, but it looks like the liver's ability to accumulate fat may somehow shield the body from the detrimental effects of other health problems such as obesity and diabetes," Lazo said in the news release.

More information

The American Liver Foundation has more about non-alcoholic fatty liver disease.