Principal Findings
comorbidity
CONGESTIVE HEART FAILURE, RECRUITMENT
We set out to describe the sociodemographic and clinical characteristics that predict enrollment in the Health eHeart Study with an email-based recruitment campaign to patients in a health system. Initial engagement rates (registration among all contacted patients) were generally low (7012/193,606, 3.6%), with higher rates among patients who are older, women, non-Hispanic White, active patients with commercial insurance or Medicare, with a higher comorbidity burden, with congestive heart failure, and randomized to receive up to 2 recruitment emails. Patterns of subsequent consent after initial registration were somewhat different (with inverse trends by age and gender), but enrollment was strongly driven by initial engagement since most initially engaged patients end up consenting to join the study (5899/7012, 84.1%). Overall, enrollment was also driven more strongly by sociodemographic than clinical factors.Email is an extremely efficient means of recruiting participants from a large list into the Health eHeart Study, a digital health study. The email recruitment campaign required relatively low operational effort from the research team and cost less than US $1000 to carry out through Mailchimp. The campaign led to 7012 patients registered, 5899 of whom consented, into the Health eHeart Study within 6 months. With access to a massive email list, the campaign was able to recruit a sufficient absolute number of total participants for most clinical trial needs. However, it also resulted in a lower proportion of patients who are racial or ethnic minorities and of lower SES. Despite email showing some advantages with recruitment, the underrepresentation of racial or ethnic minorities and those of lower SES was found to persist even at these early enrollment stages of a digital research study.