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Time protective effect of contact with a general practitioner and its association with diabetes-related hospitalisations: a cohort study using the 45 and Up Study data in Australia
  1. Ninh Thi Ha1,
  2. Mark Harris2,
  3. David Preen3,
  4. Rachael Moorin1,3
  1. 1School of Public Health, Curtin University Bentley Campus, Perth, Western Australia, Australia
  2. 2School of Economics and Finance, Curtin University, Perth, Western Australia, Australia
  3. 3School of Population and Global Health, The University of Western Australia, Perth, Western Australia, Australia
  1. Correspondence to Dr Ninh Thi Ha; thininh.ha{at}


Objectives To evaluate the relationship between the proportion of time under the potentially protective effect of a general practitioner (GP) captured using the Cover Index and diabetes-related hospitalisation and length of stay (LOS).

Design An observational cohort study over two 3-year time periods (2009/2010–2011/2012 as the baseline and 2012/2013–2014/2015 as the follow-up).

Setting Linked self-report and administrative health service data at individual level from the 45 and Up Study in New South Wales, Australia.

Participants A total of 21 965 individuals aged 45 years and older identified with diabetes before July 2009 were included in this study.

Main outcome measures Diabetes-related hospitalisation, unplanned diabetes-related hospitalisation and LOS of diabetes-related hospitalisation and unplanned diabetes-related hospitalisation.

Methods The average annual GP cover index over a 3-year period was calculated using information obtained from Australian Medicare and hospitalisation. The effect of exposure to different levels of the cover on the main outcomes was estimated using negative binomial models weighted for inverse probability of treatment weight to control for observed covariate imbalance at the baseline period.

Results Perfect GP cover was observed among 53% of people with diabetes in the study cohort. Compared with perfect level of GP cover, having lower levels of GP cover including high (incidence rate ratio (IRR) 2.8, 95% CI 2.6 to 3.0), medium (IRR 3.2, 95% CI 2.7 to 3.8) and low (IRR 3.1, 95% CI 2.0 to 4.9) were significantly associated with higher number of diabetes-related hospitalisation. Similar association was observed between the different levels of GP cover and other outcomes including LOS for diabetes-related hospitalisation, unplanned diabetes-related hospitalisation and LOS for unplanned diabetes-related hospitalisation.

Conclusions Measuring longitudinal continuity in terms of time under cover of GP care may offer opportunities to optimise the performance of primary healthcare and reduce secondary care costs in the management of diabetes.

  • continuity of care
  • primary care
  • internal medicine
  • diabetes management

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  • Contributors NTH, RM and MNH conceived the idea and study design for the manuscript. NTH conducted data analyses, and drafted and revised the manuscript. RM and MNH provided supervision and contributed in analysis, interpreting the results, drafting and revising the manuscript. DP involved in drafting and revising critically for important intellectual content of the manuscript. All authors read and approved the final version of the manuscript for publication.

  • Funding This work was supported by the National Health and Medical Research Council, project grant APP1078345.

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were involved in the design, conduct, reporting or dissemination plans of this research. Refer to the Methods section for further details.

  • Patient consent for publication Obtained.

  • Ethics approval Ethics approval was obtained from Curtin University Human Research Ethics Committee (RD-42–14) and the NSW Population and Health Services Research Ethics Committee (HREC/17/CIPHS/37). Consent was given by all participants in the Sax Institute’s 45 and Up Study for their information to be used in approved studies, and for follow-up and data linkage. The conduct of the Sax Institute’s 45 and Up Study was approved by the University of NSW Human Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement The data that support the findings of this study are available from the relevant data custodians of the study datasets. Restrictions by the data custodians mean that the data are not publicly available or able to be provided by the authors. Researchers wishing to access the datasets used in this study should refer to the Sax Institute’s 45 and Up Study process (