The Edinburgh Addiction Cohort: a longitudinal study of survival and long term injecting cessation
- J. Kimber1,2,
- L. Copeland3,
- M. Hickman1,
- J. MacLeod1,
- J. McKenzie3,
- D. D. Angelis4,
- J. R. Robertson3,5
- 1Department of Social Medicine, University of Bristol, Bristol, UK
- 2National Centre in HIV Epidemiology and Clinical Research, University of New South Wales, Sydney, Australia
- 3Muirhouse Medical Group, Edinburgh, UK
- 4MRC Biostatistics Unit, Institute of Public Health, Cambridge, UK
- 5Division of Community Health Sciences, University of Edinburgh, Edinburgh, UK
Objective
To examine survival and long term injecting cessation (LTC) in a cohort of drug users recruited in a primary care setting.
Design
Open cohort with a mean of 10.2 years (SD 6.8, range <1–25) follow-up. Data sources were primary care notes, participant interviews and linkage to the national mortality register.
Participants
794 patients with a history of injecting drug use recruited between 1980 and 2007. Their mean age at first injection was 19.9 years (SD 5.1, range 11–41). At the study endpoint, 228 (29%) were dead and 75% of survivors were followed up.
Main Outcome Measures
Time from first injection to: death; and last injection beginning a period of LTC ≥5 year’s duration.
Results
Based on a competing risks multinomial logistic regression model (n = 566), 35% of survivors did not achieve LTC, 16% died before achieving LTC, and 49% achieved LTC. The relative hazard of death before achieving LTC compared to surviving without achieving LTC decreased for those with a history of opiate substitution therapy (OST) (HR 0.19, CI 0.10 to 0.34) and increased for HIV positive participants (HR 6.2, CI 3.6 to 10.6), those who started injecting after 1985 (HR 2.5, CI 1.3 to 4.8), those aged over 18 years at first injection (HR 2.2, CI 1.4 to 3.6), and those with a history of overdose (HR 2.0, CI 1.3 to 3.2). The relative hazard of achieving LTC compared to surviving without achieving LTC decreased for those with a history of OST (HR 0.39, CI 0.27 to 0.56), those who started injecting after 1985 (HR 0.56, CI 0.39 to 0.79) and those with a prison history (HR 0.69, CI 0.54 to 0.89); and increased for those aged over 18 years at first injection (HR 1.6, CI 1.2 to 2.1).
Conclusions
Few cohorts have sufficient follow-up to measure long-term cessation. The Edinburgh Addiction Cohort (EAC) suggests that exposure to OST is protective, reducing the risk of death before long term cessation, but OST also seems to increase duration of injecting drug use, reducing the likelihood of long term cessation.
