DECLINING PREVALENCE OF INJECTION AS MAIN ROUTE OF ADMINISTRATION AMONG HEROIN USERS TREATED IN SPAIN, 1991-1993

The objetive of this study was to analyse the temporal and geographic trends and the factors associated with the prevalence of heroin inject ion (HI) in persons treated for the first time for heroin abuse/depend ence in Spain in 1991-1993. The prevalence of HI was studied in 54,132 admissions to treatment reported to the State Information System on D rug Abuse, The factors associated with HI prevalence were studied by s tratified analysis and logistic regression, Regions with similar preva lences were grouped together based on correspondence analysis, The HI prevalence declined progressively by year (50% in 1991, 43% in 1992 an d 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 preval ence group as compared with the low prevalence group, A declining tren d of HI was seen with the more recent year of first use (OR of 0.15 fo r those beginning use in the years 1991-1993 as compared with those wh o began before 1982), later age at first use and increasing years of u se, Male sex and cocaine use were associated with higher HI, Chasing i s progressively replacing injection as a route of heroin administratio n 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 thi s phenomenon. The main explanatory factors could be regional differenc es in the subculture of drug use or in the heroin market.