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Overdose Cohort Data

The BC Provincial Overdose Cohort consists of de-identified data on individuals who have experienced an opioid overdose in B.C.

Overview

Structured as a set of linked administrative datasets, information related to individuals’ overdose events is combined with data about drug prescriptions and healthcare use following the overdose event as well as from the preceding five years. This provides a longitudinal picture of individual health histories before, during and after an overdose. 

The analytic outputs will help the province to better understand factors that lead to overdose and those that contribute to overdose death. This will help better target provincial, regional and local policy and program responses to the subpopulations who are at greatest risk. Furthermore, the cohort’s products will help identify the patterns of healthcare use among those who overdose in order to identify opportunities for intervention and appropriate targeting of public health messages. 

The cohort can also be used to evaluate the impact of interventions being put in place in response to the public health emergency, as well as evaluate longer-term health outcomes of people who have overdosed. The cohort data will be refreshed annually and will be available for use by all partner organizations involved in the overdose response.

Data sources

The Provincial Overdose Cohort includes linked administrative data on health care utilization by individuals experiencing an opioid drug overdose in B.C. 

Individuals experiencing overdoses were identified using data from:

  • B.C. Ambulance Service (BCAS)
  • Drug and Poison Information Centre (DPIC)
  • BC Coroners Service (BCCS)
  • case-based reporting from emergency departments
  • National Ambulatory Care Reporting System (NACRS)
  • Discharge Abstract Database (DAD)
  • Medical Services Plan (MSP)

Five years of health history is appended at a patient level from:

  • DAD (all hospital discharge summaries)
  • NACRS (all emergency department visits)
  • MSP (all fee-for-service physician billing records)
  • PharmaNet (all prescription dispensations in community pharmacies)
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Cases

The cohort includes individuals who experienced an overdose event since January 1, 2015. This period represents the beginning of the rapid rise in opioid-related drug overdoses and deaths in B.C. 

An opioid overdose event is defined by any of the following criteria: 

  • administration of the opioid antagonist naloxone by paramedics
  • a call to DPIC about an opioid-related event
  • physician-diagnosed opioid overdose at the emergency department (from case-based reporting)
  • coroner-determined illegal drug overdose death
  • visit to hospital, emergency department or physician with an associated opioid overdose diagnosis code (from DAD, NACRS or MSP)

Related events present in multiple datasets (e.g., a single overdose involving ambulance response, transport to emergency department and admission to hospital) were grouped to prevent over counting of overdoses.

Controls

A reference population is available for analysis. These are selected from a 20% random sample of the B.C. population with overdose cases removed. A matched control population is also available. Previous cohort analyses featured 1:5 matching without replacement based on birth year, sex and Local Health Area of residence. Like the cases, health and prescribing histories are available for this group. 

Exclusions

Some individuals who experienced an opioid overdose but were unable to be linked to administrative data sources through personal health numbers were not included in the cohort (12% of all individuals). Furthermore, individuals whose overdose events were not captured through administrative data sources (i.e. those who did not access healthcare services for their overdose) will be excluded.

Potential uses

Here are some examples of potential uses of the provincial overdose cohort:

  • Analyses that require linkage: The cohort is well suited to answer questions that require information from multiple datasets. For example, a question assessing the risk of certain prescription medications among individuals with certain conditions would require the use of physician billing data, hospitalizations and prescriptions. 
  • Analyses that are longitudinal: The cohort is also a suitable dataset when analyses require that individuals be followed over time, such as investigating healthcare use patterns following an overdose.
  • Analyses that are provincial in scope or require comparison between regions: The cohort is able to provide a provincial picture of all individuals who overdose on opioids. Regional and sub-regional stratifications are possible which allows for an understanding of potential differences throughout the province.
  • Evaluation of interventions to prevent overdose: Yearly updates to the cohort are planned. As the length of follow-up grows and new interventions are implemented, it will be possible to conduct evaluations of specific interventions to better understand their effectiveness.

For more overdose response knowledge summaries and reports, see Overdose Reports.

Limitations

The cohort is not a surveillance tool as it does not have real-time information on overdose events. 

For up-to-date surveillance reports and tools, see the Overdose Data Dashboard

Only information contained in available administrative data sources can be interrogated. For instance, investigating employment histories prior to an overdose is not possible with currently available data sources.

SOURCE: Overdose Cohort Data ( )
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