The US Department of Defense Millennium Cohort Study: career span and beyond longitudinal follow-up.

OBJECTIVE To describe current and future career-span health research in the US Department of Defense Millennium Cohort Study. METHODS Collaborating with all military service branches and the Department of Veterans Affairs, the Millennium Cohort Study launched in 2001, before September 11 and the start of deployments in Afghanistan and Iraq, to conduct coordinated strategic research to determine any effects of military occupational and deployment-related exposures, on long-term health. RESULTS More than 150,000 consenting members represent demographic, occupational, military, and health characteristics of the US military. More than 70% of the first two panels have submitted follow-up questionnaires and >50% have deployed since 2001. CONCLUSIONS Prospective cohort data have identified subgroups of military populations at higher risk or more resilient to decrements in mental and physical health. Continued career span and beyond follow-up will answer long-term health questions related to military service.