AN ESTIMATE OF THE PREVALENCE OF DRUG MISUSE IN LIVERPOOL AND A SPATIAL-ANALYSIS OF KNOWN ADDICTION

Background. The objective of this study was to determine the prevalenc e and distribution of opiate and cocaine misuse in the City of Liverpo ol in 1991. The databases included residents of the city using opiates or cocaine, who were known to the Drug Dependency Units or the infect ious Diseases Unit, or who were arrested for possession of drugs in 19 91. Methods. A three-sample log-linear capture-recapture method was ap plied to databases containing details of drug users with City of Liver pool postcodes, to determine the prevalence of drug misuse in 1991. Li near regression analysis was performed to correlate the prevalence of known drug misuse with indices of material deprivation in each elector al ward. Results. Data on 1427 individuals were analysed, producing an estimate of the drug-using population of 2344 [95 per cent confidence interval (CI) = 1972-2716] and a period prevalence of 5.2 per 1000 [9 5 per cent CI = (4.5-6.0) per 1000]. In the 15-29 year age group, the prevalence of drug abuse was 16.9 per 1000 [95 per cent CI = (13.9-19. 9) per 1000]. There was a negative interdependence between the police and Drug Dependency Unit databases with attenders at the Unit being 7. 2 (95 per cent CI = 4.6-11.4) times less likely to be arrested for pos session than non-attenders. There was a strong correlation between the distribution of known drug use and material deprivation, as measured by the Townsend index (r = 0.75; p < 0.001). Conclusions. The capture- recapture method allows the prevalence of drug misuse to be estimated and provides more meaningful information than is available from the no tification system. The study suggests that people in contact with drug services are less likely to commit crimes of possession of class A dr ugs than those not in contact with drug services. There is a strong as sociation between drug abuse and deprivation, and therefore the purcha sing of services for drug misusers should be focused on areas of depri vation.