Participant attrition from statewide, population-based Survey of the Health of Wisconsin into the longitudinal SHOW COVID-19 cohort.

Purpose: Longitudinal studies are essential for examining how social and institutional determinants of health, historical and contemporary, affect disparities in COVID-19 related outcomes. The unequal impacts of COVID-19 likely exacerbated selected attrition in longitudinal research. This study examines attrition and survey mode effects in the SHOW COVID-19 study which recruited from a statewide, representative cohort.

Materials & Methods: Participants were recruited from the Survey of the Health of Wisconsin (SHOW) cohort. Online surveys, or phone interviews, were administered at three timepoints during 2020-2021. The surveys captured social, behavioral, and structural determinants of health and the lived experience. Univariate and multivariate logistic regression was used to examine predictors of participation and survey mode effects.

Results: A total of 2304 adults completed at least one COVID-19 online survey. Participants were more educated, older, and more likely to be female, married, non-Hispanic, and White compared to non-participants. Phone participants were older, less educated, and more likely be non-White, food insecure, and have co-morbidities compared to online participants. Mode effects were seen with reporting COVID-19 beliefs, loneliness, and anxiety.

Conclusion: The SHOW COVID-19 cohort offers unique longitudinal data but suffered from selected attrition. Phone interview is an important mode for retention and representation.