Penny Hill


Professor Paul Dietze, Professor Mark Stoové


Opioid overdose is a significant public health issue, with people who inject drugs (PWID) a key risk group (1). However, there is little contemporary information on opioid overdose incidence among PWID, no longitudinal studies of cumulative incidence and limited evidence of the impact of health service utilisation on incidence among PWID. My research will fill this gap through a comprehensive examination of opioid overdose using novel record-linked and self-report data from Australia’s largest cohort study of PWID, SuperMIX.


My study will examine the nature and extent of opioid overdose experienced by PWID, and identify risk and protective factors related to opioid overdose. The specific objectives of my study are to:

  1. Systematically review literature on longitudinal studies of opioid overdose
  2. Determine trajectories of opioid overdose in a cohort of PWID, with a focus on cumulative incidence
  3. Describe patterns of health service utilisation in a cohort of PWID
  4. Determine the risk and protective factors for opioid overdose among PWID, focusing on health service utilisation and behavioural factors such as patterns of drug use
  5. Determine the effectiveness of PWID-specific services in relation to opioid overdose prevention
  6. Provide updated estimates of opioid overdose related mortality among PWID


I will address the aims of my research program through the following series of studies:

Study 1: Systematic review on longitudinal patterns of opioid overdose (Objective 1)

I will conduct a review of existing research to collate, assess and interpret prior findings on longitudinal patterns of opioid overdose within populations of PWID. The review will be conducted according to standard systematic methodologies for selecting peer-reviewed and other literature, and will provide the theoretical and practical foundation for my research program.

Study 2: Determine non-fatal opioid overdose incidence in a cohort of PWID in Melbourne (Objective 2)

This study will describe trajectories of and risk and protective factors associated with non-fatal opioid overdose. Self-reported prevalence of lifetime and recent (past six months) opioid overdose within the SuperMIX cohort will be described, and longitudinal regression techniques will examine the associations between these outcomes, and socio-demographic and drug use behaviour data. This will include the first preliminary analysis of the impact of the MSIR.

Study 3: Use linked data from the SuperMIX cohort to describe the impact of health service utilisation related to opioid overdose of PWID (Objectives 3, 4 & 5)

This study will first involve the development of a comprehensive picture of health service utilisation by the cohort using self-reported and linked data. This information will then be used to evaluate the impact and association of the utilisation of various health and emergency services on the incidence of opioid overdose in the cohort. SuperMIX data has already been used to describe emergency department and hospitalisation presentations (27, 28); I will use the data to describe primary health service and ambulance utilisation of PWID. My study will be the first study to utilise Medicare Benefits Scheme (MBS)/Pharmaceutical Benefits Scheme (PBS) record linkage for a cohort of PWID in Australia.

Through this linkage, my study will be able to describe the MBS utilisation of the cohort, describe prescribed pharmaceutical use among PWID using PBS data, and also analyse linked ambulance overdose data for the cohort. My study will investigate the association between primary health care utilisation and emergency health care utilisation in regard to opioid overdose incidence. The impact of exposure to PWID-specific services such as the MSIR and whether this reduces ED and/or ambulance presentations and improves health-related quality of life will be achieved using a range of regression techniques.

Study 4: Update estimates of mortality in the SuperMIX cohort (Objective 6)

A preliminary analysis of mortality in the MIX cohort has previously been conducted that covered the period 2008-2012 (29). I will update this analysis utilising recently collected data from the cohort, with a specific focus on the relationship between mortality and health service utilisation of PWID, and the relationship between non-fatal and fatal opioid overdose among PWID in the contemporary opioid market. Mortality rates will be calculated for the cohort with standardised mortality ratios compared with Australian population estimates, and analysis using Cox regression methods will be used to determine associations between socio-demographic, drug use and health service utilisation data and mortality. This study will utilise a mix of self-report (e.g. drug use patterns) and objective (e.g. health service utilisation) exposure information with linked data from the National Death Index used to generate the mortality outcome


As opioid overdose rates among PWID and others are rapidly increasing throughout the western world, further evidence on the risk and protective factors of opioid overdose, and how to prevent these overdoses from occurring is urgently needed. My research will address major gaps in our knowledge of trajectories of opioid overdose among PWID and whether health services accessed by PWID reduces harms associated with opioid overdose and other burdens on the health system. My research is novel in that it will fill the evidence gap by investigating the cumulative incidence of opioid overdose identify preventative factors for overdose recurrence; and is the largest cohort study of PWID in Australia in a field in which most research is cross-sectional.

This study is significant in that it is the first study worldwide able to provide an objective and comprehensive description of health service utilisation of PWID, and will be the first Australian PWID-specific study to utilise record linkage from both federal (MBS, PBS, NDI) and state-level (VACIS, ADIS, VAED, VEMD) datasets. My research with the SuperMIX study will not only be able to provide unique evidence on the effectiveness of health services, but is also responsive to a change in landscape, and crucially positioned to evaluate elements of the effectiveness of the forthcoming supervised injecting facility, due to open in July 2018. 


The analyses conducted to date include a systematic review on longitudinal patterns of opioid overdose, and determining non-fatal opioid overdose among the SuperMIX cohort. 


Hill, P., Dietze, P., and Stoove, M. 2019. Predictors of baseline and recent non-fatal opioid overdose among a cohort of people who inject drugs in Melbourne, Australia at the College on Problems of Drug Dependence Annual Scientific Meeting, San Antonio, TX, USA, 2019

Hill, P., Dietze, P., and Stoove, M. 2019. Predictors of baseline and recent non-fatal opioid overdose among a cohort of people who inject drugs in Melbourne, Australia at the National Institute on Drug Abuse, [poster presentation] San Antonio, TX, USA, 2019

Hill, P., Agius, P., Stoove, M., Maher, L., Hickman, M., Kerr, T., and Dietze, P. 2019. Recent non-fatal opioid overdose: The effects of health service utilisation, alcohol and other drug use and demographic factors among people who inject drugs in Melbourne, Australia at the International Society for the Study of Drug Policy Conference, Paris, France, 22-24 May 2019.

Hill, P., Dietze, P., and Stoove, M. 2018. Correlates of non-fatal opioid overdose among a cohort of people who inject drugs in Melbourne, Australia at the Australasian Professional Society on Alcohol and other Drugs (APSAD) conference, [poster presentation] Auckland (November 2018).

Hill, P., Curtis, M., and Ward, B. 2018. All Time High Regional Roadshow: the SuperMIX study for regional Victorian community health services at Castlemaine, Maryborough, Echuca and Swan Hill (June 2018).

Horyniak, D., O’Keefe, D., Hill, P, Howell, J., Dietze, P. 2018. Trends in receptive syringe sharing and correlates of ‘ever’ sharing among a cohort of people who inject drugs regularly in Melbourne, Australia at the College on Problems of Drug Dependence Annual Scientific Meeting, [poster presentation] San Diego, CA, USA, 2018.


Hill, P, O’Keefe, D, and Dietze, P. 2018. Are there differences in individual-level needle and syringe coverage across Australian jurisdictions related to program policy? A preliminary analysis. Drug and Alcohol Review (May 2018), e-pub ahead of print.

Dietze, P., and Hill, P. 2017. Lifetime and recent opioid overdose among a sample of people who inject drugs in Australia. Sydney: National Alcohol and Drug Research Centre. (Research report, published).

Livingstone, C., Rintoul, A., de Lacy-Vawdon, C., Borland, R., Dietze, P., Jenkinson, R., Livingston, M., Room, R., Smith, B., Stoove, M., Hill, P., Winter, R. 2018. Identifying effective policy interventions to prevent gambling-related harm. Melbourne: Victorian Responsible Gambling Foundation. (Research report, submitted)


2017 – 2020


For more information relating to this project, please contact Penny Hill: