Researchers are hoping that people will do some research about where to get a tattoo, after a study found a link between body art and hepatitis C.
The new study found that people with the virus were almost four times more likely to report having a tattoo, even when other major risk factors were taken into account, co-author Dr. Fritz Francois of New York University Langone Medical Center told Reuters Health.
Although the study could not prove a direct cause and effect, "Tattooing in and of itself may pose a risk for this disease that can lay dormant for many, many years," Francois said.
About 3.2 million people in the U.S. have hepatitis C, and many don't know because they don't feel ill, according to the Centers for Disease Control and Prevention (CDC).
Hepatitis C is the leading cause of liver cancer and most common reason for liver transplants in the U.S. Some 70 percent of people infected will develop chronic liver disease, and up to 5 percent will die from cirrhosis or liver cancer.
For the current study, researchers asked almost 2,000 people about their tattoos and hepatitis status, among other questions, at outpatient clinics at three New York area hospitals between 2004 and 2006.
Researchers found that 34 percent of people with hepatitis C had a tattoo, compared to 12 percent of people without the infection.
The most common routes of contracting hepatitis C, a blood-borne disease, are through a blood transfusion before 1992 or a history of injected drug use. Injected drug use accounts for 60 percent of new hepatitis cases every year, but 20 percent of cases have no history of injected drug use or other exposure, according to the CDC.
Francois and his colleagues only included people with hepatitis C who did not contract it from these two other common sources.
After accounting for other risk factors, the difference between people with and without hepatitis was even greater, with four times as many tattoos in the infected group than for uninfected people, according to results published in the journal Hepatology.
"This is not a big surprise to me," Dr. John Levey, clinical chief of gastroenterology at the University of Massachusetts Medical School in Worcester, told Reuters Health. Earlier studies had found a link, but they were small and had not taken other risk factors into account as well as this new one did.
"This was one of the stragglers, and now we finally have some numbers for it," said Levey, who was not involved in the study.
Still, the CDC's Dr. Scott Holmberg said the link may not be quite as strong as the findings suggest, because some people who had used illegal drugs probably would not admit it, even on an anonymous questionnaire. And the researchers didn't rule out people who contracted hepatitis before getting their tattoo.
What to look for in a tattoo parlor
Holmberg, of the CDC's viral hepatitis division, recommends people only have tattoos or piercings done by trained professionals.
"In the U.S., there have been no reports of hepatitis C outbreaks linked to professional tattoo parlors," told Reuters Health by email.
In 2012, 1 in 5 people reported having at least 1 tattoo, according to a Harris poll.
"There are very reputable places that use appropriate standards," said Francois. Tattoo parlors are not federally regulated, and standards vary by state and region, so it's up to the consumer to do their homework, he said.
The Alliance for Professional Tattooists recommend finding a tattoo artist who wears disposable gloves, a clean work space without blood spatters and single-use disposable needle kits.
Levey said he wouldn't prevent his two adult daughters from getting tattoos, but he would make sure they were aware of the hepatitis C risk first.
"A lot of their friends have tattoos, it's the cool thing to do," he said. "They're adults, they can make their own decisions. But I'd mention this to them, because the long-term consequences of hepatitis C are so serious."