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. 2021 Sep 12;21(1):185.
doi: 10.1186/s12874-021-01380-0.

Strategies to maximise study retention and limit attrition bias in a prospective cohort study of men reporting a history of injecting drug use released from prison: the prison and transition health study

Ashleigh Cara Stewart  1   2 , Reece Cossar  3   4 , Shelley Walker  3 , Anna Lee Wilkinson  3   5 , Brendan Quinn  3   5 , Paul Dietze  3   5   6 , Rebecca Winter  3   7 , Amy Kirwan  3 , Michael Curtis  3   5   8 , James R P Ogloff  4 , Stuart Kinner  5   9   10   11   12 , Campbell Aitken  3   5 , Tony Butler  13 , Emma Woods  3 , Mark Stoové  3   5
Affiliations

Strategies to maximise study retention and limit attrition bias in a prospective cohort study of men reporting a history of injecting drug use released from prison: the prison and transition health study

Ashleigh Cara Stewart et al. BMC Med Res Methodol. .

Abstract

Background: There are significant challenges associated with studies of people released from custodial settings, including loss to follow-up in the community. Interpretation of findings with consideration of differences between those followed up and those not followed up is critical in the development of evidence-informed policies and practices. We describe attrition bias in the Prison and Transition Health (PATH) prospective cohort study, and strategies employed to minimise attrition.

Methods: PATH involves 400 men with a history of injecting drug use recruited from three prisons in Victoria, Australia. Four interviews were conducted: one pre-release ('baseline') and three interviews at approximately 3, 12, and 24 months post-release ('follow-up'). We assessed differences in baseline characteristics between those retained and not retained in the study, reporting mean differences and 95% confidence intervals (95% CIs). RESULTS: Most participants (85%) completed at least one follow-up interview and 162 (42%) completed all three follow-up interviews. Retained participants were younger than those lost to follow-up (mean diff - 3.1 years, 95% CI -5.3, - 0.9). There were no other statistically significant differences observed in baseline characteristics.

Conclusion: The high proportion of participants retained in the PATH cohort study via comprehensive follow-up procedures, coupled with extensive record linkage to a range of administrative datasets, is a considerable strength of the study. Our findings highlight how strategic and comprehensive follow-up procedures, frequent contact with participants and secondary contacts, and established working relationships with the relevant government departments can improve study retention and potentially minimise attrition bias.

Keywords: Attrition bias; Cohort study; People in prison; People who inject drugs.

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Conflict of interest statement

MS has received investigator-initiated funding from Gilead Sciences, AbbVie, and Bristol Myers Squibb for research unrelated to this work. PD has received investigator-driven funding from Gilead Sciences for work related to hepatitis C treatment and an untied educational grant from Indivior for work related to the introduction of buprenorphine/naloxone into Australia. He has also served as an unpaid member of an Advisory Board for an intranasal naloxone product. The remaining authors declare that they have no conflicts of interest.

Figures

Fig. 1
Fig. 1
Follow-up rates at 3, 12 and 24-months per study protocol (n = 336) and by first, second and third follow-up waves (n = 336)
See this image and copyright information in PMC

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