(Reuters Health) - Heroin use by injection has leveled off in recent years but had been rising steadily for more than a decade, a study finds.

Rates of heroin use, injection and addiction all rose steadily between 2008 and 2016, then apparently plateaued or fell slightly during subsequent years, researchers say.

The trend appears to track with rising rates of hepatitis C infection and might help explain them, said study coauthor Dr. Nora Volkow.

“We were intrigued by the idea that the opioid crisis might be behind the massive increase in hepatitis C,” said Volkow, director of the National Institute on Drug Abuse.

HIV and hepatitis infections related to injection drug use have been rising for years, Volkow and colleagues note in JAMA.

Centers for Disease Control and Prevention (CDC) data show hepatitis C infections started a sharp climb around 2010, especially among people ages 20-39.

The link between hepatitis C and heroin injections would be sharing of needles and syringes by multiple people, Volkow said. A solution to the rise in hepatitis C infections would be to make sure heroin users have access to clean needles and syringes.

“The problem is there are many places where access to clean syringes and needles is not available,” Volkow said. “What we’re seeing highlights the gap between what evidence-based practice tells us about how to protect against hepatitis C infection and what we are doing.”

To analyze rates of injected heroin use in the U.S., Volkow and colleagues turned to the annual National Surveys on Drug Use and Health, which gather information during in-person visits.

The researchers analyzed responses from 800,500 adults, average age 35, who participated in the surveys between 2002 and 2018.

They found that heroin use rose by an average of 7.5% each year between 2008 and 2016, then fell 7.1% per year between 2016 and 2018. Statistics for heroin injection and addiction followed similar patterns.

In some groups, however, injection rates continued to rise between 2002 and 2018. This was true for men and women overall, those ages 35 through 49, non-Hispanic whites and adults living in the northeast and west. Heroin injection plateaued among people ages 18 to 25 and those living in the midwest but still was higher in 2018 than in 2002.

In 2018, reported past-year heroin injection was highest among adults in the northeast and those ages 26 through 34.

There have been signs that heroin use might be plateauing or declining, said Dr. Michael Lynch, medical director of UPMC’s Pittsburgh Poison Center. In the Pittsburgh area, overdose deaths have declined by 43% compared to 2017, and national data from the CDC suggest there’s been a slight reduction in overdose deaths, he added.

Still, Lynch said, “if heroin use has plateaued, it would be when we have (it) at an all-time-horrific number. That’s not a victory. At the same time, maybe we’ve at least stopped the ongoing upward trend we’ve been seeing.”

The connection between injection rates and hepatitis C made sense to Dr. Michael Fingerhood, an associate professor of medicine and public health at the Johns Hopkins Bloomberg School of Public Health in Baltimore.

Fingerhood points to a study he did in the 1990s, in which 80% of heroin users who injected the drug were infected with a hepatitis virus. “A lot of people will draw blood back into the syringe to get the last bit of drug out. The virus lives outside the body for 24 to 72 hours and there can be millions of virus particles in the syringe.”

SOURCE: bit.ly/2OGk62z JAMA, online February 11, 2020.