U.S. military deployment during 2001-2006: comparison of subjective and objective data sources in a large prospective health study.

PURPOSE: Studies researching service members' health after deployment have relied on self-reported deployment history, although validity of these data remains unknown. This study compared self-reported and electronic deployment data and explored differences in functional health.
METHODS: Self-reported and military deployment data were compared for more than 51,000 participants enrolled in the Millennium Cohort Study (2004-2006). Kappa statistics were used to measure agreement. Analysis of variance was used to assess functional health, as measured by the Medical Outcomes Study Short Form 36-Item Health Survey for Veterans (SF-36V).
RESULTS: Of 51,741 participants who completed the initial deployment question, objective records and self-report agreed in 47,355 (92%). Agreement was substantial for deployment status, frequency, and number of deployments (kappa = 0.81, 0.71, and 0.61, respectively). Deployment start dates agreed within 1 month for 82% of participants confirmed as deployed once. Participants' Mental and Physical Component Summary scores from the SF-36V did not differ by agreement level.
CONCLUSIONS: These findings indicate substantial agreement between self-reported and objective deployment information and no clinically meaningful differences in functional health for the small proportion with inconsistent deployment information. These findings should be reassuring to investigators who examine military deployment as a determinant of future health.