US Adults' Likelihood to Participate in Dementia Prevention Drug Trials: Results from the National Poll on Healthy Aging.

Background: Recruitment to dementia prevention clinical trials is challenging, and participants are not representative of US adults at risk. A better understanding of the general public's interest in dementia prevention research participation is needed to inform future recruitment strategies.

Objective: To examine US adults' characteristics associated with self-reported likelihood to participate in dementia prevention clinical trials.

Design: We conducted a cross-sectional survey using the October 2018 wave of the University of Michigan National Poll on Healthy Aging.

Setting: The National Poll on Healthy Aging is a nationally representative survey of adults using KnowledgePanel (Ipsos Public Affairs LLC), a probability-based panel of the civilian, noninstitutionalized US population.

Participants: We analyzed data from 1,028 respondents, ages 50 to 64 years, who completed a web survey module on brain health.

Measurements: We used logistic regression models to examine associations between sociodemographic and dementia-related factors (e.g., family history) and self-reported likelihood to participate in a dementia prevention clinical trial of a new medicine ("very" or "somewhat likely" vs. "not likely" survey responses). Among respondents not likely to participate, we examined frequency of reasons endorsed for this decision, stratified by age, sex, and race and ethnicity.

Results: Of the 1,028 respondents, half were female, 68% Non-Hispanic White, 13% Hispanic, and 12% Non-Hispanic Black. Twelve percent of respondents reported being very likely to participate in a dementia prevention trial, 32% somewhat likely, and 56% not likely. Factors associated with higher likelihood to participate were higher perceived risk of dementia [OR, 2.17 (95% CI, 1.61, 2.93)], a positive family history of dementia [OR, 1.75 (95% CI, 1.27, 2.43)], and having discussed dementia prevention with a doctor [OR, 2.20 (95% CI, 1.10, 4.42)]. There were no differences in likelihood to participate by sociodemographic characteristics. Among 570 respondents not likely to participate, 39% said they did not want to be a guinea pig, 23% thought dementia would not affect them, 22% thought there would be too high a chance for harm, 15% indicated study participation would take too much time, and 5% reported fear of learning information about oneself. There were no differences across age, sex, and racial and ethnic groups.

Conclusions: In this study, perceived risk of dementia, family history, and discussion of prevention with a doctor were associated with likelihood to participate in a dementia prevention clinical trial, whereas sociodemographic factors including race and ethnicity were not. Findings suggest that recruitment interventions focused on increasing knowledge of dementia risk and prevention trials and involving healthcare providers may be effective tools to improve enrollment rates, regardless of target community.