Cumulative Stress and Health Care Utilization Among US Service Members

Importance Military personnel experience unique occupational stressors, which, combined with other life stressors, may substantially impact their health readiness. Stress exposure is known to be associated with health and health care concerns in civilian populations, but little is known as to whether these associations are present among US service members. Objective To evaluate the association between individual stressors, cumulative stress exposure, and health care utilization (HCU) among a contemporary sample of US service members. Design, Setting, and Participants This prospective cohort analysis used self-reported survey data from the Millennium Cohort Study and up to 3 years of inpatient and outpatient HCU data from Military Health System electronic health records (2020-2023) from US active-duty service members who first completed a Millennium Cohort Study baseline survey in 2020 and 2021. Data were analyzed from January to May 2026. Exposure Self-reported stress exposure (adverse childhood experiences, stressful life events, discrimination, bullying, hazing, and combat experiences) was assessed in 2020 and 2021. Main Outcomes and Measures Inpatient, outpatient, and total HCU patient-days were calculated. Negative binomial regression models examined the HCU association with cumulative and individual stress exposures, adjusting for demographic and military characteristics. Results A total of 34 731 service members were included in the analytic sample (33 252 [95.8%] were young adults aged 17-34 years; 9906 [28.5%] were female). They spent a mean (SD) of 17.74 (19.10) days (median [IQR], 12 [2-23] days) in outpatient and 0.61 (4.98) days (median [IQR], 0 [0-0] days) in inpatient care across a mean (SD) follow-up period of 2.08 (0.84) years. Higher cumulative stress exposure was associated with greater total (incidence rate ratio [IRR], 1.54; 95% CI, 1.50-1.57), inpatient (IRR, 2.28; 95% CI, 2.21-2.35), and outpatient (IRR, 1.50; 95% CI, 1.47-1.54) HCU. Individual stressors, particularly adverse childhood experiences and stressful life events, were also associated with greater HCU. Conclusions and Relevance In this cohort study of contemporary US active-duty service members, increased stress exposure was positively associated with greater HCU. Identifying and triaging various stress exposures during outpatient visits can support better access to inpatient care for service members. In turn, these efforts may translate into better patient outcomes, medical readiness, and military health system improvements.