Social networks as predictors of musculoskeletal injury in U.S. Army soldiers (SNAP-MSKI)

Abstract: Introduction: Musculoskeletal injuries (MSKIs) are the leading cause of medical non-readiness among U.S. Army Soldiers, costing the Military Health System an estimated $4.7 billion annually in direct and indirect costs. Current MSKI mitigation efforts focus on individual attributes such as body mass index and gender. However, emerging research highlights the significance of social ties on health outcomes and behaviors. This study examined the patterns of MSKI within military social networks and how social interactions, along with health behaviors such as sleep, physical activity (PA), and diet, co-occur in Soldiers with and without MSKI. Methods: Phase 1 involved a cross-sectional sociocentric social network analysis of two Army battalions (N=795; Cohort 1=413, Cohort 2=382), focusing on social interaction networks. Descriptive analyses and multivariate logistic regression with a quadratic assignment procedure were used to examine dyadic similarity in injury status, controlling for known MSKI risk factors. Phase 2 involved a 14-day ecological momentary assessment (EMA) of Soldiers with and without MSKI (n=189), capturing social interactions, interaction quality, and health behaviors. Daily morning and evening surveys assessed sleep duration and quality, and self-reported loneliness. Data were analyzed using multi-level linear and logistic regression models with mixed effects, adjusting for sociodemographic, temporal characteristics, and affective state. Results: Phase 1: Injured Soldiers were significantly more likely to spend time with other injured Soldiers than uninjured Soldiers (Cohort 1: 1.26 times (e0.227, p=.042) and Cohort 2: 1.34 times (e0.293, p=.008]). Injured Soldiers also had smaller mean degrees (Cohort 1: 3.50, Cohort 2: 3.07) compared to uninjured Soldiers (Cohort 1: 4.26, Cohort 2: 4.57). Phase 2: Soldiers were significantly more likely to engage in PA or consume food or drink when with someone. Participants also ate a greater variety of foods when with others compared to being alone. Social context did not predict sleep duration or quality. Conclusion: These findings highlight the critical role of social connections in shaping health behaviors among U.S. Army Soldiers. Injured soldiers, who had smaller social networks and were more likely to associate with other injured soldiers, underscore the need for targeted interventions to expand their social support. Future interventions and policies should consider including social context to improve MSKI outcomes in military populations.