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

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.

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.

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.

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.

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.