Guide on Selection of Optimal Motivational Themes for Use in a Clinical Trial Recruiting Black US Adults: Survey Study

Background: Black adults in the United States face significant cardiovascular health disparities, which are likely exacerbated by the underrepresentation of Black adults in cardiovascular clinical trials. The Black adult US population has experienced unique historical events, discriminatory practices, and practical obstacles that might contribute to this underrepresentation in clinical trials. An improved understanding of motivations that encourage or discourage participation in cardiovascular clinical trials can lead to more effective clinical trial recruitment and help mitigate these cardiovascular health disparities. Objective: This study aimed to determine, using an online survey, which motivational themes in clinical trial recruitment advertisements were most effective in encouraging Black adults to participate in a hypertension-focused trial. We also examined how trust in health care and various demographic factors influenced their decision to participate. Methods: We conducted an online survey with 829 self-identified Black adults in the United States, using a between-subject design to test 4 literature-derived motivational themes in clinical trial recruitment advertisements: (1) contribution to science, (2) helping the community, (3) lowering blood pressure, and (4) access to perks (US $500 worth of groceries or an equivalent cash amount). We assessed advertisement appeal, willingness to participate, and willingness to recommend clinical trial participation to others using cumulative link mixed models. Results: Demographic factors played a more significant role than motivational themes in predicting advertisement effectiveness. Adults aged 40‐59 years and individuals diagnosed with high blood pressure were more likely to find the advertisements appealing and express willingness to participate. Urban residents engaged more with the advertisements compared to those in suburban or rural areas. Participants with liberal (odds ratio [OR] 1.37, 95% CI 1.01‐1.85; =.04) and conservative (OR 1.62, 95% CI 1.09‐2.40; =.02) political views were more willing to participate in the clinical trial compared to those with moderate views. However, the “lowering my blood pressure” theme was less effective among individuals who distrusted health care institutions (OR 0.40, 95% CI 0.16‐0.97; =.04) and also reduced willingness to recommend the trial (OR 0.36, 95% CI 0.15‐0.85; =.02). In addition, higher trust levels were unexpectedly associated with lower willingness to participate when exposed to this theme (OR 0.41, 95% CI 0.17‐0.98; =.04). Conclusions: Demographic targeting (age, health status, and geographic location) is more critical than generic motivational messaging in recruiting Black adults to clinical trials. Successful digital health recruitment requires targeting specific demographic segments with tailored messages, as effectiveness varies significantly across sociodemographic factors. The online survey methodology offers researchers a rapid, scalable tool for pretesting recruitment strategies, though it should complement rather than replace community engagement. These insights can help reduce cardiovascular health disparities by improving clinical trial representativeness.