Research Report
Patterns of substance use and mortality risk in a cohort of ‘hard-to-reach’ polysubstance users
Linn Gjersing,
Anne Line Bretteville-Jensen,
Corresponding Author
Linn Gjersing
Department of Drug Policy, Norwegian Institute of Public Health, Oslo, Norway
Correspondence to: Linn Gjersing, Norwegian Institute of Public Health, Department of Drug Policy, PB 4404 Nydalen, 0403 Oslo, Norway. E-mail: [email protected]Search for more papers by this authorAnne Line Bretteville-Jensen
Department of Substance Use, Norwegian Institute of Public Health, Oslo, Norway
Search for more papers by this authorLinn Gjersing,
Anne Line Bretteville-Jensen,
Corresponding Author
Linn Gjersing
Department of Drug Policy, Norwegian Institute of Public Health, Oslo, Norway
Correspondence to: Linn Gjersing, Norwegian Institute of Public Health, Department of Drug Policy, PB 4404 Nydalen, 0403 Oslo, Norway. E-mail: [email protected]Search for more papers by this authorAnne Line Bretteville-Jensen
Department of Substance Use, Norwegian Institute of Public Health, Oslo, Norway
Search for more papers by this authorAbstract
Aims
To examine the mortality risk in a cohort of ‘hard-to-reach’ polysubstance users and its putative associations with substance use. Specifically, we estimated all-cause mortality risk as a function of individual substance use indicators, and then as a function of their complex, ‘real-life’ patterns as identified through latent class analysis (LCA).
Design
Prospective cohort study among street- and low-threshold service-recruited polysubstance users included between September and November 2013 and followed through the National Cause of Death Registry until 31 October 2015.
Setting
Seven Norwegian cities.
Participants
A total of 884 users of illegal opioids and/or stimulants. Of these, 357 were in opioid substitution treatment (OST) at the time of inclusion. Forty-four participants died during follow-up.
Measurements
Primary outcome: all-cause mortality risk. Unadjusted and adjusted Cox proportional hazard (PH) regression models (covariates: male, age, homelessness/shelter use, overdose experience, OST status, years of injecting, individual substance use indicators, city, use patterns). LCA models estimated separately for those in and those not in OST due to measurement invariance.
Findings
The crude mortality rate was 2.52 per 100 person-years. Standardized mortality ratio was 26.11 [95% confidence interval (CI) = 10.06–54.87] for women and 10.71 (95% CI = 6.39–16.81) for men. No single drug use indicator, such as ‘heroin injection’ or ‘number of drugs used’, was associated with the mortality risk. However, meaningful use patterns were identified; three OST and non-OST patterns each. The non-OST patterns ‘polysubstance injectors’ [hazard ratio (HR) = 3.45, 95% CI = 0.98–12.14] and ‘low frequent injectors’ (HR = 3.17, CI = 1.05–9.56) were associated significantly with the mortality risk even when adjusted for other known risk factors.
Conclusions
In a Norwegian prospective cohort study, ‘hard-to-reach’ polysubstance users had a more than 10 times higher mortality risk than the general population. Mortality risk was not a function of any single drug use indicator, but two distinct combinations of substances, frequencies and routes of administration were associated with the mortality risk.
Supporting Information
| Filename | Description |
|---|---|
| add14053-sup-0001-DaraS1.docxWord 2007 document , 19 KB |
Appendix S1 Model selection. Table S1 Principal indices of best fit in the latent class analysis (LCA) models within the total sample (n = 884) and thereafter separate LCA models among those in opioid substitution treatment (OST) (n = 357) and those not in OST (n = 527). |
Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
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