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. 2023 Feb 27;23(1):54.
doi: 10.1186/s12874-023-01874-z.

Recruiting and retaining community-based participants in a COVID-19 longitudinal cohort and social networks study: lessons from Victoria, Australia

Thi Nguyen  1 , Alexander J Thomas  2 , Phoebe Kerr  2 , Ashleigh C Stewart  2   3 , Anna Lee Wilkinson  2   3 , Long Nguyen  2 , Aimée Altermatt  2 , Kathryn Young  2 , Katherine Heath  2 , Anna Bowring  2 , Stephanie Fletcher-Lartey  2 , Dean Lusher  4 , Sophie Hill  5 , Alisa Pedrana  2   3 , Mark Stoové  2   3 , Katherine Gibney  6 , Margaret Hellard  2   3   6   7
Affiliations

Recruiting and retaining community-based participants in a COVID-19 longitudinal cohort and social networks study: lessons from Victoria, Australia

Thi Nguyen et al. BMC Med Res Methodol. .

Abstract

Background: Longitudinal studies are critical to informing evolving responses to COVID-19 but can be hampered by attrition bias, which undermines their reliability for guiding policy and practice. We describe recruitment and retention in the Optimise Study, a longitudinal cohort and social networks study that aimed to inform public health and policy responses to COVID-19.

Methods: Optimise recruited adults residing in Victoria, Australia September 01 2020-September 30 2021. High-frequency follow-up data collection included nominating social networks for study participation and completing a follow-up survey and four follow-up diaries each month, plus additional surveys if they tested positive for COVID-19 or were a close contact. This study compared number recruited to a-priori targets as of September 302,021, retention as of December 31 2021, comparing participants retained and not retained, and follow-up survey and diary completion October 2020-December 2021. Retained participants completed a follow-up survey or diary in each of the final three-months of their follow-up time. Attrition was defined by the number of participants not retained, divided by the number who completed a baseline survey by September 302,021. Survey completion was calculated as the proportion of follow-up surveys or diaries sent to participants that were completed between October 2020-December 2021.

Results: At September 302,021, 663 participants were recruited and at December 312,021, 563 were retained giving an overall attrition of 15% (n = 100/663). Among the 563 retained, survey completion was 90% (n = 19,354/21,524) for follow-up diaries and 89% (n = 4936/5560) for monthly follow-up surveys. Compared to participants not retained, those retained were older (t-test, p < 0.001), and more likely to be female (χ2, p = 0.001), and tertiary educated (χ2, p = 0.018).

Conclusion: High levels of study retention and survey completion demonstrate a willingness to participate in a complex, longitudinal cohort study with high participant burden during a global pandemic. We believe comprehensive follow-up strategies, frequent dissemination of study findings to participants, and unique data collection systems have contributed to high levels of study retention.

Keywords: Attrition bias; Covid-19; Longitudinal cohort study.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Typical study timeline for participants in the Optimise Study
Fig. 2
Fig. 2
Monthly recruitment intake against the seed population targets, September 012020–September 302,021
Fig. 3
Fig. 3
Completion rates of active participants over time since recruitment (months), October 012020–December 312,021. In this study participants could contribute a minimum of three-months and a maximum of 12-months follow-up time
Fig. 4
Fig. 4
Completion rates of participants over time since recruitment (months), stratified by Key people and seed participants, October 01 2020–December 312,021. In this study participants could contribute a minimum of three-months and a maximum of 12-months follow-up time
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