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Use of the CHeReL's linkage services has increased steadily since the unit was established in 2006. A list of completed projects and published research is available below.

Projects have been carried out for a broad range of purposes using data from a variety of sources. Some of the research applications of linked data have included:

  • Follow-up of cohorts of people with rare conditions or outcomes reported through population health datasets (eg. infective endocarditis, childhood cancer)
  • Morbidity and mortality associated with infectious diseases (eg. Hepatitis C, influenza) 
  • Follow up of researcher-supplied cohorts to obtain information on service utilisation or health-related outcomes (eg. 45 and Up study, the Australian Longitudinal Study on Women's Health and the HIV Observational Study Database)
  • Case control studies of cancer screening behaviour and outcomes
  • Validation of the accuracy of screening tests by linkage with outcome information (eg. antenatal serum screening and pregnancy outcomes)
  • Incidence of diseases and conditions by the identification of first-time events (eg. first admissions for stroke and heart failure)
  • Reporting of outcomes of health care adjusted for co-morbidity using historically linked data (eg. outcomes for stroke care in NSW hospitals)
  • Studies of health care safety, utilisation and costs (eg. adverse events in hospital, cancer patterns of care)
  • Validation studies of the accuracy of information held in population health datasets
  • Improved ascertainment of health information (eg. Aboriginality, diagnoses) using multiple data sources

Other purposes include population health surveillance and health system performance monitoring, where data linkage has enabled the development and monitoring of new performance indicators and strengthened the capacity of government to develop and evaluate policies and track performance over time.

The following linkage projects were completed in 2011, 2012, 2013, 2014, 2015, 2016, 2017 2018 and 2019. A list of projects completed in previous years is also available.


Long term quality of life and nutritional outcomes following oesophagectomy: Ivor Lewis oesophagectomy vs minimally invasive oesophagectomy for oesophageal cancer, A/Prof Garett Smith, Royal North Shore Hospital

There continues a rising incidence of oesophageal cancers in Australia. Most patients present with worsening dysphagia and weight loss, however roughly a third of patients already have localised disease at time of diagnosis.

In oesophageal cancer patients, alongside traditional open surgical procedures, minimally invasive oesophagectomy has been increasingly used in recent years. The open procedures are associated with increased respiratory complications and other morbidities. Studies comparing open versus minimally invasive techniques have shown no major differences in survival or quality of oncological resection.

Despite improved oncological outcomes post-surgery, patients who survive still experience significant health-related quality of life (HRQoL) issues which may also contribute to overall poor long-term survival in patients. Studies have found short-term advantages of the minimally invasive technique, however, how these patients do in the long-term is still poorly understood and reported. Through this project, the researchers intend to assess the long-term HRQoL and nutritional outcomes in patients following open Ivor Lewis or minimally invasive oesophagectomy.

The researchers identified the cohort of patients who had an oesophagectomy at a major tertiary centre between 2001 and 2017 via review of hospital medical records and existing databases. Cohort data in the Royal North Shore Hospital oesophagectomy 2001-2017 dataset were linked by the CHeReL to mortality outcome data in the NSW RBDM Death Registrations and the Cause of Death Unit record Files (COD-URF). The researchers also plan to collect data prospectively via questionnaires, blood and stool tests.

The study findings are expected to help improve understanding of patients’ quality of life and needs postoperatively and inform decision making in doctors to benefit future oesophageal cancer patients undergoing surgery. The secondary purpose of this study is to investigate the impact of oesophagectomy on patients’ nutritional status and identify important nutritional deficiencies to improve patient care. 

Using linked poisoning data for toxicovigilance and to improve care of poisoned patients, Dr Rose Cairns, University of Sydney

Several studies have demonstrated significant cost benefits of poisons centres, primarily in reducing unnecessary hospital presentations and admissions, and in improving care and reducing  length of stay of hospitalised patients. However, there are no Australian studies that comprehensively describe poisoning epidemiology across all ages and exposure types.

The New South Wales Poisons Information Centre (NSWPIC) is Australia’s largest poisons centre, taking calls from healthcare professionals and members of the public. There is limited systematic information regarding NSW poisons centre service utilisation.

The researchers of this retrospective cohort study plan to use data linked via the CHeReL to analyse patterns in poisons centre service utilisation and factors affecting utilisation to help PIC guideline development and service planning.  A methodological study analysing poisoning case ascertainment in different health datasets is also planned. Geographic variation in poisonings will be studied for targeted prevention initiatives and deaths post-discharge for poisoning patients will be examined to provide guidance on the safety of driving after discharge, and guide mental health follow-up post overdose.

The cohort for this study includes NSW patients affected by poisoning, with poisoning-related records in any of the following: the NSW Poisons Information Centre (NSW PIC), Admitted Patient Data Collection (APDC), Emergency Department Data Collection (EDDC), Cause of Death Unit Record Files (COD-URF) and NSW Ambulance dataset. The CHeReL supported the study by identifying the cohort and linking cohort data from these datasets to poisoning data held by the NSW Poisons Information Centre.

Overall, the program of work is expected to provide a comprehensive overview of poisoning in NSW.

Determining the health and welfare use of New South Wales workers with long duration workers’ compensation claims (the Transitions study), Prof Alex Collie, Monash University

This study aims to examine the health care and welfare (social security) use of a group of more than 4000 injured workers in New South Wales with very long periods of time off work, whose income support through the NSW workers' compensation scheme ceased in late 2017 due to changes in the state workers' compensation legislation (the Section 39 cohort).

The retrospective case-controlled cohort study will examine the extent and nature of healthcare use and welfare use in the Section 39 cohort at the conclusion of their income support and for a 12- month period after withdrawal of income support in the workers’ compensation system. Health and welfare outcomes will be compared to an injured worker control group and a community control group.

The planned analysis dataset includes state and Commonwealth datasets which were linked and accessed via the CHeReL and AIHW respectively. The Section 39 cohort and injured worker comparison group were identified by the State Insurance Regulatory Authority of NSW (SIRA) and a potential community control group was identified by linkage to the Medicare Enrolment File by the AIHW. The CHeReL linked the cohort to NSW hospitalisation data from the Admitted Patient Data Collection (APDC) and the Emergency Department Data Collection (EDDC). The AIHW linked the Department of Social Security interactions of the cohort, medical benefits and pharmaceutical benefits from the Data Over Multiple Individual Occurrences (DOMINO) dataset, the Medicare Benefits Schedule (MBS) and Pharmaceutical Benefits Schedule (PBS) respectively.

The study is expected to provide new information about health and welfare outcomes of injured workers, on the impact of a major social policy change, and will for the first time examine interactions between Australian systems of income support and healthcare for injured workers.

The Antecedents of Renal Disease in Aboriginal Children and Young People (ARDAC): Understanding and moderating the trajectory towards chronic disease in young Aboriginal people, Professor Jonathan Craig, Flinders University

Addressing the gap in health between Aboriginal and non-Aboriginal Australians is a national health priority. Approximately 50% of this gap can be attributed to diseases linked by common risk factors, namely cardiovascular disease (CVD), diabetes mellitus (DM), and chronic kidney disease (CKD). As such, it is important to consider the interrelated nature of these conditions, their determinants, and their burden.

The ARDAC Study commenced in 2002 and is population-based study of 3758 participants recruited during early childhood with 57% of participants identifying as Aboriginal. The ARDAC study aims to identify early childhood factors associated with the emergence of chronic conditions over the life course. As the largest cohort study of its kind, with strong Aboriginal governance, the ARDAC Study investigates the effects of childhood hypertension, diabetes, cardiovascular, kidney health, and modifiable health risk behaviours and socio-demographic factors on overall life course outcomes between Aboriginal and non-Aboriginal participants in the ARDAC cohort.

To achieve its aims, the ARDAC study has linked its cohort data to over 20 statewide data collections via CHeReL, including the Perinatal Data Collection (PDC), Perinatal Death Reviews (PDRs), NSW APDC, NSW EDDC, Ambulance eMR/ PHCR, BDMRs, NAPLAN & ANZDATA. Commonwealth data, including the MBS and PBS data collections, was linked and provided by the Australian Institute for Health and Welfare.

With the ARDAC cohort now young adults, aged between 18 to 30 years of age, the study will address the current evidence gap for this age group for who data on chronic disease health and wellbeing are currently limited. Addressing this evidence gap is crucial because early adult life is a critical transition period for the development of chronic disease. As such, the ARDAC data linkage will generate definitive evidence on the life course trajectories for chronic conditions from childhood to early adult life among Aboriginal Australians.

Late postoperative complications after childhood hypospadias repair performed in three Children's hospitals in New South Wales between 1991 and 2006, Dr Peter Pockney, Dr Aniruddh Deshpande John Hunter Hospital

Hypospadias is the most common congenital penile anomaly. Most diagnosed children undergo surgical correction in early childhood as a single or two-stage procedure, with the aim to achieve both functional (urinary and sexual) and cosmetic normalcy.

There is currently limited knowledge on long-term outcomes of hypospadias repair, particularly the incidence and type of subsequent penile interventions. Filling this knowledge gap will help understand the risk factors of future complications requiring intervention and devise preventative strategies and improve the care of hypospadias patients of all ages.

This retrospective data linkage study included a cohort of children operated on for hypospadias in three NSW Children's hospitals between 1991 and 2005. The cohort was produced from the Medical Record Departments based on the pre-selected diagnostic and procedure codes. The CHeReL linked the cohort to the NSW APDC and EDDC to identify individuals who subsequently had penile surgery at any age between 2001 and 2020 in public or private hospitals in NSW.

The linked data will be used to analyse the incidence and type of the unplanned subsequent penile procedures and identify potential risk factors (e.g., severity of hypospadias, type of repair, presence of persistent chordee, division of the urethral plate etc.). The researchers also aim to conduct a time-to-event analysis of subsequent penile procedures. By ascertaining potential risk factors for future long-term complications and the researchers expect to be able to propose interventions to mitigate them.

Generating evidence for a strong foundation in the early years: using population health data for translational child health, healthcare and policy, Professor Natasha Nassar, University of Sydney

Long-term health, developmental and educational outcomes of many perinatal and early childhood conditions are largely unknown. These include infants born prematurely, or with other medical conditions, or born to mothers with disorders of immune or endocrine systems. Children experiencing acute or chronic health conditions or injuries throughout childhood, and undergoing subsequent procedures or interventions are also at increased risk of complications, including impacted neurodevelopment.

This data linkage project seeks to establish an Australian birth cohort of routinely collected and linked population perinatal, health, development, and education data of infants born in NSW from 1994-2015.  The proposed research will utilize the cohort data to investigate the impact of early life events on subsequent child health, development, and healthcare utilization.

The specific aims of this project, for each condition or intervention, are to assess the burden of disease, assess maternal and infant characteristics and risk factors of infants with each condition, examine health outcomes, health service utilisation and associated costs for infants with and without each condition/ intervention and investigate association between presence of condition/ intervention and developmental, educational, neurodevelopmental, and mental health outcomes.

The CHeReL identified the cohort for this retrospective study consisting of infants and their mothers from NSW PDC from 1994 onwards and from all APDC separations up to age 25 years old (0-24 years at admission). The CHeReL linked cohort data to hospital and emergency admissions in the NSW APDC and EDDC respectively, death data from the RBDM and COD-URF and to the Mental Health Ambulatory Collection data. Several other datasets such as out-patients dataset, the Neonatal Intensive Care Units Study (NICUS), Register of Congenital Conditions (RoCC), NSW Mental Health Outcomes & Assessment Tools Data Collection (MH-OAT data), NSW Board of Studies NAPLAN, school attendance and HSC, Department of Family & Community Services Disability Services and Operating Room Datasets were also linked to create a comprehensive dataset.

This cohort will provide the opportunity to investigate emerging issues in child and adolescent health on a population level.

Mortality and hospitalisation outcomes of young people in primary mental health care: a 10 year follow up study, Professor Ian Hickie, University of Sydney

Understanding the risk of death from suicide in people experiencing mental distress is essential for delivering targeted clinical interventions as well as interventions at a population level. Recent analyses provide support to a disproportionate increase in emergency department presentations related to self-harm and suicidal behaviour presentations.

The data linkage study aims to establish mortality and hospitalisation outcomes over a ten-year period in a population of young people engaged in primary mental health care services. The researchers aim to establish rates of death from suicide and other causes, such as accident and injury, and where substance use or intoxication was a contributing factor, as well as rates of presentation to emergency departments and hospital admissions. The secondary aim of this study is to establish rates of presentation to emergency departments and hospital admissions.

To achieve this, mortality and hospital outcomes were linked to data already collected as part of a longitudinal study of 7000 young people (aged 12-30 years old) conducted by Brain and Mind Centre. Young people- aged between 12 and 30 years at first presentation, who attended at least one visit to the service, and consented to participate in the Brain and Mind Research Patient Register constituted the study cohort. The cohort dataset included sociodemographic, clinical, and functional data that were collected at baseline and at subsequent visits to the health service. Baseline neuroimaging and neurocognitive assessments that were available for a subset of 1000 patients will be used to identify predictors of mortality and hospitalisation outcomes. The CHeReL facilitated the study by linking cohort data to hospital and emergency admissions in the NSW APDC and EDDC respectively, death data from the RBDM and COD-URF.

Health service utilisation and outcomes following surgery for Inflammatory Bowel Disease, Professor Jane Young, University of Sydney

 Australia has one of the highest incidences of inflammatory bowel disease (IBD) in the world. While many patients with IBD can be managed with medical therapy, a few require surgery. These surgeries include those performed as an emergency operation (for example, an emergency colectomy), or those performed electively (including ileal pouch surgery).

The first part of this retrospective data linkage study looks to assess outcomes of patients undergoing IBD surgery. All individuals undergoing surgery for IBD admitted to NSW hospitals from July 2001 to March 2019 constituted the study group. Previous Australian studies in this cohort have limited to hospital based / single-centre studies. This study looks to use NSW administrative (APDC) data, linked with mortality data, to assess trends, outcomes, and health service utilisation in patients undergoing surgery for IBD, with the overall aim of identifying potential areas for improvement and ways of minimising ‘unwanted’ variation in outcomes following this surgery.

The second part of this study aims to validate the APDC to investigate outcomes of IBD surgery. A prospective database of all individuals undergoing ileal pouch surgery for IBD by a single surgeon and admitted to Royal Prince Alfred Hospital (RPAH), Sydney, from July 2001 to March 2019 (Ileal Pouch database) will be supplemented by comprehensive medical records review for each patient within the database and used for validation. By comparing this data to the APDC data, the accuracy of the APDC in terms of case ascertainment and diagnosis of complications can be determined. This validation study is important to guide future use of the APDC in investigating patients undergoing IBD surgery.

The CHeReL facilitated this study by identifying the cohort of all individuals in the APDC who had been diagnosed with IBD or had undergone surgery for IBD and in the Ileal Pouch database to their hospitalisation data in the APDC and death data in the NSW RBDM and COD-URF.

Macquarie MINDS: Monitoring of Injury and psychosocial health outcomes, career trajectories and continuing educatioN, LiveD experiences and Social connectedness, Dr Reidar Lystad, Macquarie University

The period from late teens to adulthood can have significant impact on the future health and well-being of individuals. The Macquarie Minds study aims to establish a large, prospective longitudinal cohort of young adults and routinely capture information on their life experiences and exposures and assess their impact on education, employment, lifestyle, health-related quality of life, well-being, social support, life events, carer responsibilities, and use of social media technology. The study findings could potentially be instrumental in understanding the determinants of healthy and resilient individuals in our society.

The pilot cohort study aims to determine the feasibility of recruiting university graduates to establish the longitudinal cohort study. The specific objectives of linking administrative health data are to determine the proportion of consented participants that can be matched to the Master Linkage Key; and to determine the proportion of such matched participants who have relevant health records in each of the data collections.

The cohort consists of Macquarie University graduates in 2018 who consented to participation in surveys and data linkage. University graduates are used as a proxy for the population of interest (i.e., emerging adults) as it allows convenient recruitment of a clearly defined cohort (i.e. graduates from a single university in a single calendar year). Primary cohort data were collected through an online registration form, baseline, and follow-up surveys and linked by the CHeReL to hospital data from NSW APDC and NSW EDDC and to NSW eMR, NSW PHCR, NSW Central Cancer Registry, NSW RBDM Death Registrations and Cause of Death Unit Record File.

The data linkage will enable the researchers to investigate individual and social factors associated with health outcomes and service use (ambulance, emergency department, hospitalisation, cancer registry, and mortality records).

Mapping the care pathway of youth and adolescents that self-harm in the Australian Capital Territory, A/Prof Alice Richardson, Australian National University

Self-harm is relatively common among young people with prevalence rates reported in adolescent samples ranging from 7.3 to 16.1%. Studies in New South Wales and Victoria found that