Locating longitudinal study participants 10 years after last contact: Contemporary approaches to sample retention

Despite their advantages, longitudinal studies often face high rates of attrition. This study documents the extensive efforts associated with retaining a longitudinal cohort last contacted 10 years earlier.

We examine the processes and outcomes of attempts to reach 1736 individuals who have been part of a multiwave study about growing up in Ontario, Canada. Contact methods include email, phone, text, social media, postal mail, announcements in newspapers, subway stations, and music streaming services.

Challenges included a lack of consistent annual communication with participants, children moving out of the parental home, and changes in email addresses and phone numbers. The most effective contact method was phone; text messages and friend referrals were the least effective. Overall, 41.5% of the original sample was reached. Locating former research participants years later necessitated multiple and repeated contact attempts, and intensive human resources.

Ten lessons for effective sample retention are discussed. In summary, reducing attrition depends on a comprehensive study design and an organized and flexible protocol that adapts to a study's ever-changing needs.