Estimating the number of people who inject drugs (PWID) in Europe

Background

The Problem Drug Use (PDU) indicator is one of the five EMCDDA key epidemiological indicators (KI), which consist of five domains that address key aspects of the prevalence and harms of drug use at the European level. This poster is part of a set of five posters on the five EMCDDA key epidemiological indicators. Within the PDU indicator, national experts from 30 countries (the PDU network) provide prevalence estimates of high-risk drug use by substance and the prevalence of injecting drug use (IDU). IDU is associated with a high burden of diseases through mortality and morbidity, and knowing the size of the population of PWID is important for service planning. PWID size is one of the core indicators for monitoring the elimination of viral hepatitis. Here we present the latest estimates of the number of people who inject drugs (PWID) in EU30 countries.

Methods

People who inject drugs were defined as people who have injected any psychoactive substance(s) not according to medical prescription in the last 12 months. In practice, PWID belong to hard-to-reach groups imperfectly covered by probabilistic surveys. National experts therefore used indirect statistical methods such as treatment or mortality multiplier and capture recapture to estimate the prevalence of IDU. The European total was based on the sum of country-specific estimates provided by national focal points adjusted by Eurostat population. When no recent national estimate was available, we imputed the missing value with proxies from local estimates, treatment data, prevalence of high-risk opioid use or using the EU average.

Results

Estimates from 2011 onwards were available for 18 EU30 countries. At national level, the size of PWID population ranged from less than 1 to more than 10 cases per 1 000 population aged 15–64 years. For these 18 countries, the estimated total number of PWID was 410 000, corresponding to a prevalence of IDU of 2.26 per 1000 inhabitants aged 15-64.

Conclusions and recommendations

Indirect statistical methods are based on many assumptions (independence of data sources, homogenous populations) that are not always met. Comparability between countries should be considered carefully due to the different methods and data sources used. While the size of the PWID population is useful to provide policy makers with the size of a population in need harm reduction interventions and treatment, the information is still missing for 12 EU30 countries.