Methodological challenges of using U.S. Army administrative data to identify a cohort of basic combat trainees and descriptive analysis of trends in characteristics that are potential risk factors for training-related injury.

Objectives: Training-related injury is a threat to military health and readiness. Prevalence of potential risk factors for training-related injury can change with U.S. Army recruitment goals and may influence basic combat training (BCT) injury rates. This article describes challenges of using administrative data to identify a trainee cohort and describes demographic and training characteristics across the five BCT locations.

Methods: Data from the Total Army Injury and Health Outcomes Database were used to identify a U.S. Army-wide cohort of first-time trainees from January 1, 2002 to September 30, 2007 and describe its characteristics.

Results: The cohort includes 368,102 first-time trainees. The annual number starting BCT increased from 52,187 in 2002 to 68,808 in 2004. The proportion of males increased from 81.57% in 2003 to 83.84% in 2007. Mean (SD) age increased from 20.67 (3.55) years in 2002 to 20.94 (3.65) years in 2007. Mean (SD) body mass index increased from 24.53 (3.56) kg/m(2) in 2002 to 24.94 (3.84) kg/m(2) in 2006. Other characteristics fluctuated by year, including proportions of race/ethnicity, accession waivers, and confirmed graduates.

Conclusions: Fluctuations in trainee characteristics warrant further analysis of potential influence on BCT injury rates. For research uses, careful acquisition of administrative data is needed.