JMIR Publications

ABSTRACT

Background:

Generation Scotland (GS) is a genetic family health cohort study established in 2006 (N~24,000). A new wave of recruitment was initiated in 2022 aimed at adding a further 20,000 new participants to the cohort using online data collection and remote saliva sampling (for genotyping and DNA methylation profiling). Eligible individuals included anyone living in Scotland aged over 12 years. New participants give consent for linkage to their medical and administrative records, and to provide a saliva sample for DNA. The current study evaluates the different strategies employed to recruit new participants to the GS cohort for those aged 16+ (recruitment of ages 12-15 will be presented separately due to additional strategies).

Objective:

This study aimed to evaluate recruitment strategies employed to recruit new participants to the GS cohort. Recruitment strategies were compared in terms of overall numbers as well as sociodemographic characteristics of the recruits, sample return rates and cost-effectiveness.

Methods:

From May 2022 to the end of December 2023 recruitment was undertaken by the following methods: snowball recruitment (through friends and family of existing volunteers), invitations to those who participated in a previous survey during the pandemic (CovidLife: the GS COVID-19 impact survey) and Scotland-wide recruitment through social media (including sponsored Meta advertisements), news media and TV advertisement. Method of recruitment was self-reported by participants in the baseline questionnaire.

Results:

Over the above period, 7,889 new participants were recruited to the cohort. According to the different strategies, this included, in order: social media (N=2,436, 30.9%), CovidLife survey responder invitations (N=2,049, 26.0%), TV advertising (N=1,367, 17.3%), snowball (N=891, 11.3%), news media (N=747, 9.5%) and other methods/unknown (N=399, 5.0%). More females signed up than males (70.5% female participants). To date, 83.5% of participants have returned their postal saliva sample. Sample return varied between demographic factors (>60 years 90.5% vs 16-34 years 71.1%). The average cost per participant across all recruitment strategies was £13.52. Past survey invitations (CovidLife) were most cost-effective at £0.37 per recruit, social media cost £14.78 per recruit, whilst TV advertisement recruitment was the most expensive at £33.67.

Conclusions:

We present the challenges and successes of recruitment of new participants to a large ongoing cohort using remote assessment. Besides targeting existing survey responders, social media advertising has been the most cost-effective and easily sustained strategy for recruitment. We note different strategies resulted in successful recruitment over varying timescales (e.g. consistent sustained recruitment for social media, and large spikes for news media and TV advertising) which may be informative for future studies with different requirements of recruitment periods. Limitations include self-reported methods of recruitment, and difficulties in capturing multi-layered recruitment. Overall, these data demonstrate the potential cost requirements and effectiveness of different strategies that could be applied to future research studies. Future work will report success and challenges of recruitment activities aimed at younger individuals, under 16 years.