Capture-recapture estimates of problem drug use and the use of simulation based confidence intervals in a stratified analysis

Abstract

Setting and participants: Problem drug users aged 16-54 resident within Greater Manchester who attended community based statutory drug treatment agencies, were in contact with general practitioners, were assessed by arrest referral workers, were in contact with the probation service, or arrested under the Misuse of Drugs Act for offences involving possession of opioids, cocaine, or benzodiazepines. Design: Multi-sample stratified capture-recapture analysis. Patterns of overlaps between data sources were modelled in a log-linear regression to estimate the hidden number of drug users within each of 60 area, age group, and gender strata. Simulation methods were used to generate 95% confidence intervals for the sums of the stratified estimates.Main results: The total number of problem drug users in Greater Manchester was estimated to be 19 255 giving a prevalence of problem drug use of 13.7 (95% CI 13.4 to 15.7) per 1000 population aged 16-54. The ratio of men to women was 3.5:1. The distribution of problem drug users varied across three age groups (16-24, 25-34, and 35-54) and varied between the 10 areas. Conclusions: Areas in close geographical proximity display different patterns of drug use in terms of prevalence rates and age and gender patterns. This has important implications, both for future planning of service provision and for the way in which the impact of drug misuse interventions are evaluated.

Is urbanization a risk factor for substance misuse?

“…In confirming this, Gemmell et al (27) aimed at establishing the prevalence of problem drug use in the 10 local authorities within the Metropolitan County of Greater Manchester between April 2000 and March 2001 using a multisample stratified capture-recapture analysis. The total number of problem drug users in Greater Manchester was estimated to be 19 255 giving a prevalence of problem drug use of 13.7 per 1000 population aged 16-54.…”

The Role of Community-Mindedness in the Self-Regulation of Drug Cultures

“…In recent years, levels of injecting in the UK seem to have been relatively stable (cf. Gemmell et al 2004 ; ) .…”

How well do trends in incidence of heroin use reflect hypothesised trends in prevalence of problem drug use in the North West of England?

“…In a parallel study to that described here (Gemmell, Millar, & Hay, 2004), PDU period prevalence estimates were obtained for 2000-2001 for each of the ten local government areas within Greater Manchester, an urban conurbation in North West England with a population of around 2.5 million. As in previous UK studies (Beynon et al, 2001;Hickman et al, 1999;Wood, Bloor, & Palmer, 2000), a problem drug user was defined as: 'A person who experiences social, psychological, physical, or legal problems related to intoxication and/or regular excessive consumption and/or dependence as a consequence of his/her own use of drugs or chemical substances' the definition was refined to include only users of opiates, cocaine and/or benzodiazepines.…”