Back to News

Sources: MedpageToday.com, Journal of the American Medical Association (Vol. 296 No. 1, July 5, 2006)

New Study Estimates One Third of US Adults Have Liver Disease

A new study finds that there is a growing incidence of liver disease in the general U.S. population.

More than one-third of U.S. adults (37.6%) had liver disease as evidenced by elevated alanine aminotransferase (ALT) levels. These results are found in the general population, after those with risk factors such as hepatitis B or C infection, a history of alcohol abuse, or iron overload were excluded, according to Matthew Cave, M.D., of the University of Louisville in Kentucky.

The announcement of this study documenting the meteoric rise in the number of US adults with liver disease comes just days after the FDA announced that the pain killer, acetaminophen, should carry stricter warning labels about the risk of liver damage.

This FDA action comes just one month after US regulators mandated modifying the label requirements on the drug to convey stronger warnings of the risk of liver damage . The new laws may limit the dosage in individual pills and require different pediatric dosage and drug measurement devices, since the warning labels have not been able to curb the skyrocketing disease levels.

Previous epidemiological studies have found that drugs are now the most common cause of liver failure in the United States. 

A study published in the July 5, 2006 issue of the Journal of the American Medical Association indicated that acetaminophen use, even at recommended doses, causes liver damage. In the study, the use of the acetaminophen increased ALT levels to nearly five times normal in 19% of the 145 participants.

Dr. Cave’s attributed at least some of the skyrocketing liver disease numbers to exposures to environmental pollutants, including banned organochloride pesticides and heavy metals such as mercury and lead.

"These results indicate that there may be a previously unexpected role for environmental pollution in the rising incidence of liver disease in the U.S. population," Dr. Cave said. "This is the first study to my knowledge, epidemiologic study anyway, that shows that this is a problem," he added.

He will present the findings at Digestive Disease Week. On the basis of the results, Dr. Cave estimated that 70 million U.S. adults have liver disease not explained by the traditional risk factors of hepatitis b and c, alcohol abuse and iron overload.

Previous work by Dr. Cave's group has established a link between high occupational exposures to chemicals and liver disease, but it had remained unknown whether chronic, low-level exposure to chemicals was associated with liver abnormalities in the general population.

So, using data from the National Health and Nutrition Examination Survey (NHANES) for 2003-2004, the researchers identified adults with detectable levels of 196 different pollutants in their blood or urine.

Only the 111 toxicants present in 60% or more of the participants were included in the analysis.

After excluding participants with known risk factors for liver disease, researchers found that nearly 40% had elevated ALT levels.

Increasing levels of heavy metals and pesticides were both associated with higher odds of having elevated ALT levels after adjusting for age, sex, race, poverty, insulin resistance, and body mass index.

Participants who had the highest levels of mercury had double the risk of an elevated ALT, the surrogate measure for liver disease and those who had the highest levels of lead had triple the risk.

The major route of exposure for many of the pollutants included in the study is through the food supply, he said, and once they are in the body, they are not well metabolized.

Organochloride pesticides in particular accumulate in adipose tissue, so that individuals who are more overweight have higher levels, Dr. Cave said.

He pointed out, however, that a cross-sectional analysis cannot prove causality. One could argue, he said, that patients with liver disease are less capable of metabolizing these pollutants, and that explains the higher levels.

But animal studies have shown that these pesticides and other pollutants cause liver disease, he said.

"So I believe that it's very plausible that these caused the liver disease" in this study, he said.