Abstract
INTRODUCTION: Recruitment of participants for intervention studies is challenging. We evaluated the effectiveness and efficiency of a participant recruitment campaign through an online registry for the FINGER-NL study, a multi-domain lifestyle intervention trial targeting cognitively healthy individuals aged 60-79 with dementia prevention potential. Additionally, we explored which recruitment strategy successfully reached individuals from underrepresented groups in research. METHODS: The campaign entailed seven recruitment strategies referring to The Dutch Brain Research Registry (DBRR): (1) Facebook advertisements, (2) appearance on national television, (3) newspaper articles, (4) researcher outreach, (5) patient organizations, (6) search engines, and (7) other. For each strategy, we describe the number of individuals (a) registered, (b) potentially eligible, and (c) included in FINGER-NL. Subsequently, the efficiency, defined by the eligibility ratio (eligible/registered), and effectiveness, defined by the inclusion ratio (included/registered) were calculated. Associations between recruitment strategies and sociodemographic factors of underrepresented groups were tested with binomial logistic regressions. RESULTS: The campaign resulted in 13,795 new DBRR registrants, of which n = 3475 were eligible (eligibility ratio = 0.25) and n = 1008 were included (inclusion ratio = 0.07). The Facebook advertisements and television appearance resulted in the highest numbers of registrants (n = 4678 and n = 2182) which translated to the highest number of inclusions (n = 288 and n = 262). The appearance on national television (eligibility ratio = 0.35), newspaper articles (0.26), and Facebook campaigns (0.26) were the most efficient strategies. The national television appearance (inclusion ratio = 0.13) was the most effective strategy. The Facebook campaign and appearance on national television performed relatively better in recruiting individuals from underrepresented groups. DISCUSSION: A multipronged recruitment campaign via a national online recruitment registry is efficient and effective in recruiting and prescreening an adequate number of individuals aged 60-79 years with prevention potential for a multi-site intervention trial within a limited time frame of 15 months. Social media advertisements and television are preferred strategies to recruit individuals from underrepresented groups. HIGHLIGHTS: An online brain research registry recruited eligible participants successfully.Mass media recruitment strategies are efficient for reaching large numbers.Direct recruitment through researchers and patient organizations seems more effective.Online registries offer automated prescreening and alternatives for screen-failures.Tailored strategies are needed to reach underrepresented groups to improve diversity.