Digital and traditional recruitment strategies and participation patterns in the multicenter Healthy Brain Ageing study.

BACKGROUND: Early detection of Parkinson's disease (PD) benefits from innovative approaches such as large-scale online surveys on different risk factors in the general population. Effective dissemination is essential, yet little is known about the relative reach and recruitment patterns of different strategies. OBJECTIVE: To describe dissemination strategies used in the multicenter Healthy Brain Ageing (HeBA) study and characterize center-specific recruitment-source, web-access, demographic, and survey-completion patterns across three European centers. METHODS: Data from three centers (Barcelona, Spain; Luxembourg, Luxembourg; and Innsbruck, Austria) aiming at remotely identifying PD risk factors and prodromal symptoms were analyzed. Dissemination strategies were categorized as digital or traditional. Descriptive statistics summarized dissemination strategies, geographic web-access patterns, linguistic adaptation, recruitment sources, and survey completion. RESULTS: At the campaign level, digital dissemination predominated in Barcelona (55.7%) and Luxembourg (53.3%), whereas Innsbruck used a slightly higher proportion of traditional campaigns (52.2%). Participant-reported recruitment sources showed center-specific patterns: digital advertising was the most frequent reported source in Barcelona (62.5%), flyers or invitation letters in Luxembourg (39.3%), and radio or television in Innsbruck (31.4%). Sex-based recruitment differences were significant in Luxembourg (p = 0.006) and Innsbruck (p = 0.009), and age-based differences were significant in all centers (Barcelona p < 0.001, Luxembourg p < 0.001, Innsbruck p = 0.001), with 82.0% of participants younger than 65 years. The proportion of participants in the high questionnaire-completion category (≥90% of items answered) was 77.1% in Barcelona, 94.5% in Luxembourg, and 92.8% in Innsbruck. CONCLUSIONS: Recruitment-related patterns differed across centers and reflected locally implemented combinations of digital and traditional dissemination channels. These findings suggest that recruitment strategies for large-scale online health studies may benefit from considering local media ecosystems, language contexts, and digital participation patterns.