Comprehensive Health Predictors of Injury, Illness, and Separation From Service After Enrollment in Special Forces Assessment and Selection: A Two-Year Longitudinal Study.

Individuals in physically and cognitively demanding professions face increased risk of injury, illness, and attrition due to repeated exposure to physical and psychological stressors. Identifying modifiable factors associated with these outcomes can guide risk mitigation strategies. This longitudinal study examined the 2-year cumulative incidence of injuries, illnesses, and attrition following enrollment in the United States Army Special Forces Assessment and Selection (SFAS) course (n = 792) and assessed how physical, nutritional, cognitive, sleep, and social support at the time of enrollment were associated with illness, injury, and attrition outcomes. Upon SFAS enrollment, candidates completed psychological, sleep, and nutrition surveys. Anthropometrics and physical performance were assessed, and fasted blood was collected for physiological and nutritional biomarker analyses. Medical encounters and active-duty status were monitored for all candidates, post 2 years enrollment, regardless of SFAS outcome. Logistic regression identified baseline factors associated with 2-year incidence of injury, illness, or attrition. Slower road march times were associated with 25%-66% higher odds of injury, mental or behavioural illness, sleep disorder, and separation from service. Conversely, greater resistance training, better sleep quality, and higher protein intake were associated with 18%-45% lower odds of injury. Elevated morning cortisol at enrollment was associated with 23% lower odds of mental or behavioural illness, whereas negative mood, poorer sleep quality, and less social support were each associated with increased odds of separation by 28%-31%. This study identified modifiable factors that may be targeted to reduce injury and illness and improve resilience and retention in demanding occupations.