For U.S. injection drug users (IDUs) living with hepatitis C, high levels of the virus and increased risk of liver cancer and liver disease have been linked with age, race, ethnicity and gender, as well as HIV coinfection, according to a new study published in the journal Hepatology and reported in a U.S. National Cancer Institute statement.

For the study, researchers from the National Cancer Institute examined about 1,700 black, Latino and white injection drug users living with hepatitis C in six San Francisco Bay area neighborhoods between 1998 and 2000. Scientists recruited an ethnically and sexually diverse group, but roughly 75 percent of participants were men and 56 percent were African American. The average age at which participants first used injection drugs was 18.

To check what type of hep C virus participants had and how much of the virus was present (called the hepatitis C RNA level), scientists took blood and DNA samples from each individual in the group. (HCV RNA levels can also help predict a patient’s response to treatment and his or her risk of liver cancer and liver disease.)

“With such a high incidence and prevalence of hepatitis C virus infection among IDUs, it’s important to understand the infection’s characteristics in this group,” said Thomas O’Brien, MD, MPH, a senior investigator in the Division of Cancer, Epidemiology and Genetics at the National Cancer Institute in Rockville, Maryland.

Researchers found that older black male IDUs tended to have higher hep C RNA levels. In addition, individual demographic factors, such as being older, male and of African ancestry, were also linked to higher levels of the virus. (IDUs coinfected with HIV also had elevated hep C RNA levels.)

“We know that the level of [hepatitis C virus] is an important predictor of treatment response,” O’Brien concluded, adding that “these levels seemed to be influenced by a number of demographic, clinical, viral and human genetic factors.”

Some HCV treatments may work better for African Americans who don’t typically respond well to standard therapy. Click here to read about two new hep C treatments.