USING GEOGRAPHIC INFORMATION-SYSTEMS TO ASSESS SPATIAL PATTERNS OF DRUG-USE, SELECTION BIAS AND ATTRITION AMONG A SAMPLE OF INJECTION-DRUG USERS

This study sought to assess whether frequency and type of drug use are geographically located within the city of Baltimore independent of ne ighborhood characteristics. The second goal was to assess geographic f actors associated with sample selection and attrition. The sample cons isted of 597 inner-city injection drug users who were enrolled in a HI V prevention study. The residential locations were plotted using Geogr aphic Information Systems (GIS) software. Three patterns of drug use i n the prior 6 months were examined: daily use of injection heroin, dai ly use of injection cocaine and any use of crack cocaine. Daily use of cocaine and any use of crack were found to be statistically associate d with residing in the western portion of the city and distance from t he western district sexually transmitted disease clinic. After adjusti ng for individual level characteristics and neighborhood level variabl es, as measured by 1990 census tract data, daily use of cocaine was fo und to be associated with residing in a more southern area of the city and distance from the western district sexually transmitted disease c linic, and any crack use was found to be associated with residing in a more western area of the city and distance from the western district sexually transmitted disease clinic. Men and younger participants were more likely to reside further away from the study clinic as were indi viduals who dropped out of the intervention condition. The results of this study suggest that type and frequency of drug use is associated w ith specific geographic areas, independent of neighborhood characteris tics. These results have implications for the location of drug prevent ion, needle exchange and other HIV prevention activities. (C) 1998 Els evier Science Ireland Ltd. All rights reserved.