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Factors associated with non-participation in one or two follow-up phases in a cohort study of injured adults
  1. John Desmond Langley1,
  2. Rebbecca Lilley1,
  3. Suzanne Wilson1,
  4. Sarah Derrett1,
  5. Ari Samaranayaka1,
  6. Gabrielle Davie1,
  7. Shanthi N Ameratunga2,
  8. Emma H Wyeth3,
  9. Paul Hansen4,
  10. Brendan Hokowhitu5
  1. 1Injury Prevention Research Unit, Department of Preventive and Social Medicine, University of Otago, Dunedin, Otago, New Zealand
  2. 2Section of Epidemiology and Biostatistics, School of Population Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
  3. 3Ngāi Tahu Māori Health Research Unit, Department of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand
  4. 4Department of Economics, University of Otago, Dunedin, New Zealand
  5. 5Faculty of Native Studies, University of Alberta, Edmonton, Alberta, Canada
  1. Correspondence to Dr Sarah Derrett, Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, PO Box 56, Dunedin 9054, New Zealand; Sarah.Derrett{at}


Objective To identify factors associated with non-participation at the 12-month and 24-month follow-up phases of a prospective cohort study of injury outcomes.

Methods Associations between non-participation at follow-up phases and a range of sociodemographic, injury, health, outcome and administrative factors were examined.

Results An individual's non-participation at 12 months did not necessarily mean non-participation at 24 months. Sociodemographic factors were the most salient for non-participation, regardless of the number of follow-up phases or specific phase considered.

Conclusions Retention rates in prospective cohort studies of injury outcome may be improved by follow-up of everyone irrespective of previous non-participation, focusing resources to retain men, young adults, indigenous people and those living with people other than family members, and by ensuring that multiple alternative participant contacts are obtained. There is sufficient evidence to be concerned about potential bias given that several of the factors we, and others, have identified as associated with non-participation are also associated with various functional and disability outcomes following injury. This suggests detailed investigations are warranted into the effect non-participation may be having on the estimates for various outcomes.

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