Deployment, combat, and risk of multiple physical symptoms in the US military: a prospective cohort study

Multiple physical symptoms (MPS) have historically been observed after deployment to a combat zone and are often disabling in nature. This study examined longitudinal trends in MPS status and its relationship to deployment in U.S. military service members.

Using longitudinal data from panel 1 participants in the Millennium Cohort Study (n = 76,924), MPS status was assessed at three time points (2001-2008) using the 15-item Patient Health Questionnaire. Probability of reporting MPS was analyzed using mixed-effects multinomial logit regression, with time and deployment experience as main explanatory variables.

After adjustment for demographic, military, and health characteristics, service members who deployed with combat were significantly more likely to report MPS at each time point compared with those not deployed (odds ratio [OR] and 95% confidence interval [CI] for wave 1 = 1.49 [1.47-1.52], wave 2 = 1.73 [1.69-1.78], wave 3 = 2.08 [2.03-2.12]), and those who deployed without combat (OR and CI for wave 1 = 2.66 [2.59-2.74], wave 2 = 1.81 [1.75-1.87]; wave 3 = 1.68 [1.63-1.74]).

Longitudinal trends indicate that the probability of reporting MPS has increased consistently over time only for those deployed, regardless of combat experience.