Participant Satisfaction and Engagement With a Military Longitudinal Cohort Study: The U.S. Millennium Cohort Study

Service members and veterans remain a challenging population for survey research. As the Millennium Cohort Study is the largest and longest running prospective cohort study in United States military history and has follow-up data collection planned through 2068, it is critical to determine factors that may help bolster participant retention.

A satisfaction survey was administered in 2023 to obtain feedback for quality improvement efforts. Of the eligible Millennium Cohort Study participants, 27,224 (45%) completed the satisfaction survey. Chi-square tests were used to examine responses stratified by service status (active duty, Reserve/National Guard, and veterans). Natural language processing was utilized to uncover latent topics from open-text data.

A majority of respondents (96%) were satisfied with their experience in the study. The main motivations for continued participation included helping fellow service members and veterans (96%) and learning about military health issues (82%). Major topics that emerged in open-ended feedback provided by 25% of the sample included the importance of tracking health outcomes related to military exposures, a desire to help service members and veterans, and a desire to see study results and impacts.

Altruism toward the military community was a key motivation for continued participation and efforts to highlight these values may help to increase study recruitment and retention.