Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in context

Summary: Background: The age of people who inject drugs appears to be increasing in some high-income countries. We aimed to explore trends in the age of people injecting and recently starting to inject drugs in Australia, and to model incidence of initiation over time. Methods: We obtained data fro...

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Main Authors: Olivia Price, Lisa Maher, Amy Peacock, Farzaneh Zolala, Louisa Degenhardt, Paul Dietze, Sarah Larney, Seraina Agramunt, Samantha Colledge-Frisby, Bradley Mathers, Dan Lewer, Rachel Sutherland
Format: Article
Language:English
Published: Elsevier 2025-04-01
Series:The Lancet Regional Health. Western Pacific
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Online Access:http://www.sciencedirect.com/science/article/pii/S2666606525000859
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author Olivia Price
Lisa Maher
Amy Peacock
Farzaneh Zolala
Louisa Degenhardt
Paul Dietze
Sarah Larney
Seraina Agramunt
Samantha Colledge-Frisby
Bradley Mathers
Dan Lewer
Rachel Sutherland
author_facet Olivia Price
Lisa Maher
Amy Peacock
Farzaneh Zolala
Louisa Degenhardt
Paul Dietze
Sarah Larney
Seraina Agramunt
Samantha Colledge-Frisby
Bradley Mathers
Dan Lewer
Rachel Sutherland
author_sort Olivia Price
collection DOAJ
description Summary: Background: The age of people who inject drugs appears to be increasing in some high-income countries. We aimed to explore trends in the age of people injecting and recently starting to inject drugs in Australia, and to model incidence of initiation over time. Methods: We obtained data from the Illicit Drug Reporting System (IDRS) and the Australian Needle Syringe Program Survey (ANSPS), which comprise annual cross-sectional surveys with people who inject drugs (2000–2019). Outcome measures were current age, age of initiation, and time since initiation (both surveys), and drug first injected (IDRS only). We estimated time trends in age using quantile regression. We used the relative number of people initiating injecting drug use each year and existing population size estimates to model incidence of initiation. Findings: In total, 58,465 interviews with people who reported injecting drugs in the past month (33.7% women) were included. In both surveys, the median age increased over the study period (IDRS: 28–43 years; ANSPS 28–44 years). The median time since initiation also increased over the study period (IDRS: 8–22.5 years; ANSPS: 9–24 years), and the median age of initiation increased with calendar year of initiation (IDRS: 18–34 years; ANSPS: 20–30 years). Women tended to be younger and commence injecting drug use at a younger age than men. Modelling suggested that similar numbers of people injected drugs for the first time each year from 1980 (national estimates of 15,570 and 17,020 new initiates using IDRS and ANSPS data, respectively) to 1996 (IDRS: 16,360; ANSPS: 22,300 new initiates), followed by a decisive decline in incidence until 2012 (IDRS: 1110; ANSPS: 1830), whereafter it has fluctuated but remained low. Meth/amphetamine was consistently the predominant drug injected at initiation among IDRS participants, although there were peaks in heroin as the drug injected at initiation in the early 1980s and mid-1990s. Interpretation: In 2019, most people who were injecting drugs in Australia were part of a cohort that began injecting in the 1980s or 1990s. Consequently, the population was older and had been injecting drugs for longer compared to those injecting drugs in 2000. This has implications for health service delivery to people who inject drugs, with increasing age likely to be accompanied by a rise in chronic health conditions and an increase in injecting duration potentially resulting in higher incidence of injecting-related injuries and diseases. Funding: Australian Government Department of Health and Aged Care.
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spelling doaj-art-fea628cade0440dd9baf3b4bd265bb392025-08-20T02:17:41ZengElsevierThe Lancet Regional Health. Western Pacific2666-60652025-04-015710154810.1016/j.lanwpc.2025.101548Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in contextOlivia Price0Lisa Maher1Amy Peacock2Farzaneh Zolala3Louisa Degenhardt4Paul Dietze5Sarah Larney6Seraina Agramunt7Samantha Colledge-Frisby8Bradley Mathers9Dan Lewer10Rachel Sutherland11National Drug and Alcohol Research Centre, UNSW Sydney, Sydney, Australia; Corresponding author. National Drug and Alcohol Research Centre, 22-32 King Street, Randwick, NSW, 2031, Australia.Kirby Institute, UNSW Sydney, Sydney, Australia; Burnet Institute, Melbourne, AustraliaNational Drug and Alcohol Research Centre, UNSW Sydney, Sydney, Australia; School of Psychological Sciences, University of Tasmania, Hobart, AustraliaPublic Health Intelligence, Queensland Department of Health, Herston, AustraliaNational Drug and Alcohol Research Centre, UNSW Sydney, Sydney, AustraliaBurnet Institute, Melbourne, Australia; National Drug Research Institute, Curtin University, Melbourne, Australia; National Drug and Alcohol Research Centre, UNSW Sydney, Sydney, AustraliaCentre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Canada; Department of Family Medicine and Emergency Medicine, Faculty of Medicine, University of Montréal, Montréal, CanadaNational Drug Research Institute, Curtin University, Perth, Australia; Kurongkurl Katitjin, Edith Cowan University, Perth, AustraliaNational Drug and Alcohol Research Centre, UNSW Sydney, Sydney, Australia; National Drug Research Institute, Curtin University, Melbourne, AustraliaKirby Institute, UNSW Sydney, Sydney, AustraliaBradford Institute for Health Research, Bradford, UK; Department of Epidemiology and Public Health, University College London, London, UKNational Drug and Alcohol Research Centre, UNSW Sydney, Sydney, AustraliaSummary: Background: The age of people who inject drugs appears to be increasing in some high-income countries. We aimed to explore trends in the age of people injecting and recently starting to inject drugs in Australia, and to model incidence of initiation over time. Methods: We obtained data from the Illicit Drug Reporting System (IDRS) and the Australian Needle Syringe Program Survey (ANSPS), which comprise annual cross-sectional surveys with people who inject drugs (2000–2019). Outcome measures were current age, age of initiation, and time since initiation (both surveys), and drug first injected (IDRS only). We estimated time trends in age using quantile regression. We used the relative number of people initiating injecting drug use each year and existing population size estimates to model incidence of initiation. Findings: In total, 58,465 interviews with people who reported injecting drugs in the past month (33.7% women) were included. In both surveys, the median age increased over the study period (IDRS: 28–43 years; ANSPS 28–44 years). The median time since initiation also increased over the study period (IDRS: 8–22.5 years; ANSPS: 9–24 years), and the median age of initiation increased with calendar year of initiation (IDRS: 18–34 years; ANSPS: 20–30 years). Women tended to be younger and commence injecting drug use at a younger age than men. Modelling suggested that similar numbers of people injected drugs for the first time each year from 1980 (national estimates of 15,570 and 17,020 new initiates using IDRS and ANSPS data, respectively) to 1996 (IDRS: 16,360; ANSPS: 22,300 new initiates), followed by a decisive decline in incidence until 2012 (IDRS: 1110; ANSPS: 1830), whereafter it has fluctuated but remained low. Meth/amphetamine was consistently the predominant drug injected at initiation among IDRS participants, although there were peaks in heroin as the drug injected at initiation in the early 1980s and mid-1990s. Interpretation: In 2019, most people who were injecting drugs in Australia were part of a cohort that began injecting in the 1980s or 1990s. Consequently, the population was older and had been injecting drugs for longer compared to those injecting drugs in 2000. This has implications for health service delivery to people who inject drugs, with increasing age likely to be accompanied by a rise in chronic health conditions and an increase in injecting duration potentially resulting in higher incidence of injecting-related injuries and diseases. Funding: Australian Government Department of Health and Aged Care.http://www.sciencedirect.com/science/article/pii/S2666606525000859AgeingDemographyEpidemiologyInjecting drug useModellingAustralia
spellingShingle Olivia Price
Lisa Maher
Amy Peacock
Farzaneh Zolala
Louisa Degenhardt
Paul Dietze
Sarah Larney
Seraina Agramunt
Samantha Colledge-Frisby
Bradley Mathers
Dan Lewer
Rachel Sutherland
Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in context
The Lancet Regional Health. Western Pacific
Ageing
Demography
Epidemiology
Injecting drug use
Modelling
Australia
title Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in context
title_full Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in context
title_fullStr Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in context
title_full_unstemmed Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in context
title_short Changing age profile and incidence of injecting drug use initiation among people in Australia who inject drugs: evidence from two national repeated cross-sectional studiesResearch in context
title_sort changing age profile and incidence of injecting drug use initiation among people in australia who inject drugs evidence from two national repeated cross sectional studiesresearch in context
topic Ageing
Demography
Epidemiology
Injecting drug use
Modelling
Australia
url http://www.sciencedirect.com/science/article/pii/S2666606525000859
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