Age and sharing of needle injection equipment in a cohort of Massachusetts injection drug users: an observational study

BACKGROUND Hepatitis C infection (HCV) among individuals aged 15-24 years has increased in Massachusetts, likely due to injection drug use. The prevalence of injection equipment sharing (sharing) and its association with age was examined in a cohort of out-of-treatment Massachusetts substance users. METHODS This analysis included baseline data from a behavioral intervention with substance users. Younger and older (<25 versus ≥ 25 years) injection drug users were compared on demographic characteristics, substance use practices, including factors present during the most recent sharing event ("event-level factors"), and HCV testing history. RESULTS Sharing was reported by 41% of the 484 individuals who reported injection drug use in the past 30 days. Prevalence of sharing varied by age (50% <25 years old versus 38% ≥ 25 years, p=0.02). In a multivariable logistic regression model younger versus older individuals had twice the odds of sharing (95% CI=1.26, 3.19). During their most recent sharing event, fewer younger individuals than older had their own drugs available (50% versus 75%, p<0.001); other injection event-level factors did not vary by age. In the presence of PTSD, history of exchanging sex for money, or not being US born, prevalence of sharing by older users was higher and was similar to that of younger users, such that there was no association between age and sharing. CONCLUSIONS In this cohort of injection drug users, younger age was associated with higher prevalence of sharing, but only in the absence of certain stressors. Harm reduction efforts might benefit from intervening on mental health and other stressors in addition to substance use. Study findings suggest a particular need to address the dangers of sharing with young individuals initiating injection drug use.