Science Communication & Media
Sociodemographic Factors Associated with Withdrawal from a National Brain Health Cohort Azmat Sidhu* Azmat Sidhu Sidhu Sidhu University of Arizona
Background:
Internet-based cohorts are critical for brain health research, but participant withdrawal threatens representativeness and longitudinal follow-up. In digital studies, email unsubscription provides a measurable indicator of disengagement. We examined sociodemographic factors associated with withdrawal from MindCrowd, a national online brain health cohort.
Methods:
We conducted a retrospective cohort study of U.S. MindCrowd participants engaged in automated email communications between June 2022 and August 2025. Adults (≥18 years) with valid email addresses were included. The outcome was confirmed email unsubscription. Predictors included age, sex, race, Hispanic/Latino ethnicity, education, number of chronic conditions, and neighborhood socioeconomic vulnerability (CDC Social Vulnerability Index). Logistic regression models estimated unadjusted and adjusted odds of unsubscription.
Results:
Among 80,930 participants, 4,615 (5.7%) unsubscribed. Mean time to unsubscription was 71.6 days. Older age was strongly associated with withdrawal; participants aged 70–79 (aOR=1.94, 95% CI: 1.64–2.29) and ≥80 (aOR=2.24, 95% CI: 1.80–2.80) had higher odds compared with ages 18–29. Black participants (aOR=0.59, 95% CI: 0.50–0.69) and Hispanic/Latino participants (aOR=0.77, 95% CI: 0.69–0.87) were less likely to unsubscribe than White and non-Hispanic participants. Higher education was associated with greater withdrawal, while residence in highly socioeconomically vulnerable areas was associated with lower odds of unsubscription (aOR=0.83, 95% CI: 0.74–0.92). Sex and chronic conditions burden were not independently associated.
Discussion:
Withdrawal from a national online brain health cohort is socially patterned. Targeted, age- and education-sensitive engagement strategies may reduce attrition and improve representativeness in large-scale digital brain health research.
