Women Far More Likely to Get HCV Infection Via Injection Drugs

Women are at a significantly greater risk for Hepatitis C (HCV) infection via drug injection than men, according to a new study that draws questions to the role of hormones in infectious disease contraction.

Researchers found in data of 1,868 people that women who inject drugs are at a 38% greater risk of contracting HCV than men who inject drugs. Although HCV can be commonly contracted through the sharing of syringes and other injections equipment, noted differences in these behaviors did contribute to the greater rate of women contraction found in the study.

An adjusted female-to-male hazard ratio (HR) for HCV infection was found with a Cox proportional hazard model. Calculated behavioral and demographic risk factors used to adjust the HR had little change on the disparity, researchers noted.

What could make a difference in the HR are elements not yet measured by research.

“Multiple factors, including biological (hormonal), social network, and differential access to prevention services, may contribute to increased HCV susceptibility in women who inject drugs,” researchers wrote.

The study was funded by the National Institute on Drug Abuse (NIDA) of the National Institutes of Health (NIH). Researchers pulled data from the International Collaboration of Incident HIV and HCV in Injecting Cohorts — a project of pooled biological and behavioral data from 10 prospective cohorts of people who inject drugs.

NIDA deputy director Wilson Compton said he was “intrigued and impressed” by the study’s ability to track HCV patients when they were first infected. Infection dates were estimated on a hierarchy of successive data — serological, virological, and clinical results.

HIV, another virus transmitted through infected syringe equipment, has been found to be “modestly higher” in women, Compton noted. Other infectious conditions, especially bacteria-based diseases, do not have a similar sex ratio to HCV or HIV.

“There is some indirect connection that it may spread in women more so,” Compton said. “That’s what unique about this study, is it looks at exposure to the virus.”

Though there’s no previous data to suggest hormonal differences in men and women plays a role in HCV infection, Compton believes the epidemiology study has led researchers to pursue that idea as a clue.

“It’s possible it could be an indirect affect,” Compton said. “The changes of drug abuse on hormonal levels could account for increasing risks at times.”

NIH also called for follow-up research into immune cell composition between the sexes, among other uncertain indications.

“For example, it is unclear why enrollment in medication assisted treatment programs for opioid addiction reduced the risk for contracting HCV to a greater extent in men than in women,” NIH wrote in a press release.

Compton expressed concern about the discovery, within scope of the opioid epidemic. Neonatal exposure rates have increased in past years, and pregnant women injecting drugs bring equal risk to themselves and their fetus.

“Hopefully we can do a better job of treating these conditions,” Compton said.

The study, "The effect of female sex on hepatitis C incidence among people who inject drugs: results from the international multi-cohort InC3 Collaborative," was published online in Clinical Infectious Diseases this month.

A press release regarding the study was made available.

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