Declining prevalence of injection as main route of administration among heroin users treated in Spain, 1991-1993

Abstract

The objetive of this study was to analyse the temporal and geographic trends and the factors associated with the prevalence of heroin injection (HI) in persons treated for the first time for heroin abuse/dependence in Spain in 1991-1993. The prevalence of HI was studied in 54,132 admissions to treatment reported to the State Information System on Drug Abuse. The factors associated with HI prevalence were studied by stratified analysis and logistic regression. Regions with similar prevalences were grouped together based on correspondenc e analysis. The HI prevalence declined progressively by year (50% in 1991,43% in 1992 and 38% in 1993). The regions were grouped into 3 geographic areas, with rising prevalences in the southwest-northeast. Region was the factor most strongly asociated with HI, with an OR of 6.17 in the high prevalence group as compared with the low prevalence group. A declining trend of HI was seen with the more recent year of first use (OR of 0.15 for those beginning use in the years 1991-1993 as compared with those who began before 1982), later age at first use and increasing years of use. Male sex and cocaine use were associated with higher HI. Chasing is progressively replacing injection as a route of heroin administration because new users primarily use this route and probably because the most common transition is from injecting to chasing. The impact of the HIV epidemic and control programmes does not sufficiently explain this phenomenon. The main explanatory factors could be regional differences in the subculture of drug use or in the heroin market. T, he injecting use of heroin is the major cause of the spread of HIV infection in Spain. Over 60% of reported AIDS cases have been transmitted by sharing injection material and it is estimated that the HIV prevalence in injectors ranges from 40 to 70%. Thus, temporal trends in the injecting use of heroin are probably one of the most important factors influencing the evolution of the HIV epidemic and knowledge of these trends is essential in designing and implementing policies for prevention and control. A national study' found that in 1991 injection was the main route of administration for 64.4% of heroin users at the time of admission to out-patient treatment. This study revealed 2 important facts: first, the existence of considerable regional differences in the prevalence of the injecting use of heroin as the main route of administration in persons admitted for treatment for heroin abuse or