Recruitment Methods, Inclusion, and Successful Participation in a Longitudinal Clinical Trial Using Ecological Momentary Assessment

Underrepresentation of historically marginalized populations in clinical trials continues to threaten the validity of health intervention research. Evidence supports the merits of intercept and other proactive forms of recruitment for achieving more equitable representation. However, researchers also report lower retention and adherence to protocols among these populations, particularly in longitudinal studies. Few studies have compared recruitment methods for longitudinal randomized trials testing health interventions, with even fewer having done so for trials involving ecological momentary assessment (EMA). As intervention research integrates EMA and other data collection approaches requiring substantial participant effort, it is critical to better understand the effectiveness and implications of strategies to improve the representativeness of health research. This secondary data analysis compared outcomes of proactive and reactive recruitment strategies (mobile lab intercepts and internet/flyer advertising, respectively) in study inclusion, task completion, and retention within a 14-day randomized controlled trial that used EMA to evaluate cigarette package health messages. Proactive recruitment resulted in higher proportions of participants with low income and education, limited health literacy, and of diverse racial/ethnic makeup. However, this recruitment method also resulted in lower task completion, especially in the second week of the trial period, and lower retention, although group differences were not explained by participant sociodemographic characteristics targeted by inclusion efforts. We conclude that proactive recruitment via intercepts is an effective strategy for health intervention research that aims to include stakeholders from historically marginalized groups but that researchers and funders must recognize these methods require additional resources, considerations, and capacity to address non-trivial challenges to successful participation.