Although longitudinal cohort studies remain the gold standard for examining cause effect relationships, their limitations include participant attrition and significant resource requirements for cohort recruitment and follow-up. Attrition is commonly reported in prospective studies where participants are hard to trace for follow-up research (Masson, Balfe, Hackett, Phillips, et al. 2013; Mychasiuk & Benzies, 2011). The past couple of decades have seen remarkable advancements in information systems including new platforms that have contributed to an evolution in participant recruitment and tracing methods. Web search phone directories that were used in research to successfully trace cohort participants (Barakat-Haddad et al., 2009; Kleschinsky et al., 2009) have now become less useful or obsolete. Currently, Social Networking Sites (SNS) are often used for participant recruitment (Barakat et al, 2022) and may be promising tools for participant tracing and retention. Home to millions of users, SNS have revolutionized the global community by enhancing social communication and connection between users. This widespread use of SNS may also help mitigate challenges related to participant tracing and attrition in longitudinal cohort studies, including offsetting financial burdens and reducing efforts and time needed to trace lost participants.

This pilot study investigates the effectiveness of using SNS to trace lost participants from an earlier cohort study, the Hamilton Cohort Study (HCC) (n=3202, 1976-1986), as well as a related reconstructed cohort study, the Reconstructed Hamilton Children Cohort (RHCC) (n=397, 2005-2007). Participants were 6 to 8 years old at recruitment to the HCC study, and the median age was 36 years for the RHCC. Although 71% of the original sample were lost to follow-up, this was largely related to changes to parental contact information, mainly telephone numbers and addresses. Following approval from the Ontario Tech University Research Ethics Board, we used Facebook and LinkedIn to search for HCC participants by name. Overall, 21% of original participants were traced to unique profile pages indicating successful tracing, 69% were traced to multiple pages, and 10% were lost to follow-up. The pilot project led to important lessons learned, for example, participant engagement was more effective using LinkedIn than Facebook, particularly when a premium account was purchased where viewership increased by three-folds. Facebook is most effective when paid targeted advertisements are boosted. Hashtags have the potential to increase reach, particularly given that pilot study results suggest that a large proportion reside in Hamilton (77%), Burlington (2%), Toronto (2%), and Stoney Creek or Ancaster (1%). In addition, many can be traced to McMaster University (10%), Mohawk College (28%), Sir Winston Churchill Secondary School (2%), Westmount Secondary School (3%), as well as other secondary schools. To our knowledge, no research has explored the effectiveness of using SNS to trace participants after decades of no contact. 

Findings from this study will advise on the effectiveness of using SNS for participant recruitment, tracing, and reengagement, and may contribute to knowledge on the importance of mining historical cohort databases for longitudinal research.