Frequency of injecting among people who inject drugs: A systematic review and meta-analysis

People who inject drugs (PWID) do so at varying frequencies. More frequent injecting is associated with skin and soft tissue infection, blood borne viruses, and overdose. The aims of this review are to estimate the prevalence of injecting frequency among PWID and compare these estimates to current needle-syringe distribution coverage estimates, and identify socio-demographic and risk characteristics, and harms associated with daily or more injecting.

We conducted a systematic review of the peer-reviewed and grey literature from 2008 to 2018 and extracted needle-syringe distribution coverage data from a recent systematic review. We generated country-, region-, and global-level estimates of daily or more injecting. We also ran meta-regression analyses to determine associations between daily or more injecting and socio-demographic characteristics, injecting risk behaviour, non-fatal overdose, injection site skin infection, and blood borne virus prevalence.

Our search resulted in 61,077 sources, from which 198 studies were eligible for inclusion in this review. There were 74 countries with estimates for injecting frequency. Globally, we estimated that 68.1% (95%CI 64.5-71.6%) of PWID, equating to approximately 10.5 (95% UI 6.8-15.0) million people, inject daily or more frequently. There was a higher percentage of participants reporting daily or more injecting among samples with shorter injecting careers, more male participants and higher reporting of opioids as their main drug injected. Daily or more injecting was also associated with samples reporting a higher prevalence of HIV and hepatitis C antibody (anti-HCV), non-fatal overdose, and receptive needle sharing in the previous month.

WHO recently recommended a needle-syringe distribution target of 300 needles per PWID per year which is unlikely to be sufficient for the majority of PWID injecting daily or more who are out of drug treatment.

The Australian National Drug and Alcohol Research Centre, Australian National Health and Medical Research Council, University of New South Wales.