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  1. A. Kamps1,
  2. J. Runhaar1,
  3. M. de Wilde2,
  4. M. de Ridder2,
  5. J. van der Lei2,
  6. S. Swain3,4,
  7. W. Zhang3,
  8. D. Prieto-Alhambra4,
  9. M. Englund5,
  10. E. de Schepper1,
  11. S. M. A. Bierma-Zeinstra1,6
  12. on behalf of FOREUM Comorbiditis in Osteoarthritis
  1. 1Erasmus Universty Medical Center, Department of General Practice, Rotterdam, Netherlands
  2. 2Erasmus Universty Medical Center, Department of Medical Informatics, Rotterdam, Netherlands
  3. 3University of Nottingham, School of Medicine, Nottingham, United Kingdom
  4. 4University of Oxford, Nuffield Department of Primary Care Health Sciences, Oxford, United Kingdom
  5. 5Lund University, Clinical Epidemiology Unit, Lund, Sweden
  6. 6Erasmus Universty Medical Center, Department of Orthopedics & Sports Medicine, Rotterdam, Netherlands


Background Osteoarthritis (OA) is a common and disabling disease that places a significant burden on both patients and health care systems. Previous studies have already shown that patients with OA have a higher risk of developing comorbidities. However, many focused on one or a few conditions only, or did not consider the chronology of the disease onset relative to OA.

Objectives To determine the risk of physician-diagnosed comorbidity following the diagnosis of knee or hip OA, using electronic health records in the Netherlands.

Methods A cohort study was conducted using the Integrated Primary Care Information (IPCI) database, an electronic health record database with medical records of 2.5 million patients from Dutch general practice. The study population consisted of patients aged 18 years or older, that were at risk for incident OA and comorbidity. Diagnosis of knee or hip OA (i.e. exposure) was defined as the first registration of the corresponding diagnostic code from the International Classification of Primary Care (ICPC) coding system in the medical record. Fifty-eight long-term comorbidities (i.e. outcome) were selected and defined by their corresponding ICPC codes.

Patients’ follow-up started after registration in the database, and ended at the diagnosis date of the comorbidity (i.e. event), or at deregistration, death or at December 31st, 2019 (i.e. censoring), whichever came first. Exposure to knee or hip OA was a time-varying exposure: time between the start of follow-up and diagnosis of OA was defined as unexposed time, and between diagnosis of OA and the end of follow-up as exposed time. Patients’ age was used as time axis to correct for age non-linearly. Sex-adjusted hazard ratios (HRs) comparing exposed and unexposed patient status were estimated with 99.9% confidence intervals (CI).

Results The study population consisted of 1,890,712 patients. For 11 of the 58 studied comorbidities exposure to knee OA showed a statistically significant HR larger than 1, indicating an increased risk of being diagnosed with these comorbidities after a diagnosis of knee OA. For none of the comorbidities there was a statistically significant negative association (HR<1) with exposure to knee OA. For 7 comorbidities exposure to hip OA showed a statistically significant HR larger than 1. Again, for all other comorbidities the HR of hip OA was non-significant. For an overview of the statistically significant positive associations see Table 1.

Table 1.

Comorbidities with significant HRs of exposure to knee or hip OA

Conclusion This study showed that certain comorbidities were diagnosed more often in patients exposed to knee or hip OA, and none were less frequently diagnosed in patients exposed OA. This suggests that the management of OA should consider the risk of other long-term-conditions and that further research on causality between OA and comorbidity is needed.

Acknowledgements We thank the Patient Research Participants members Jenny Cockshull, Stevie Vanhegan, and Irene Pitsillidou for their involvement in the project. We would like to thank the FOREUM for financially supporting the research.

Disclosure of Interests None declared

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