Risk factors of persistent insomnia among survivors of traumatic injury: a retrospective cohort study

Study Objectives: Insomnia is a diagnosis with broad health and economic implications that has been increasingly recognized in military service members. This trend was concurrent with an increase in traumatic wartime injuries. Accordingly, we sought to determine longitudinal predictors of persistent insomnia in combat veterans who sustained traumatic injuries. Methods: Retrospective cohort study of service members deployed to conflict zones from 2002 to 2016, with longitudinal follow-up in the Veterans Affairs and Military Health Systems. Two cohorts were derived: (1) service members who sustained traumatic injuries and (2) an age-, sex-, and service component-matched cohort of uninjured service members who deployed to a combat zone. Insomnia was defined using International Classification of Diseases, Ninth Revision or International Classification of Diseases, 10th Revision-Clinical Modification codes. Results: The final population of 17,374 service members was followed from date of injury (or date of matched participant's injury) for a median of 8.4 (interquartile range, 5.3-10.7) years. Service members with traumatic injury were at significantly greater risk of developing insomnia than uninjured service members (hazard ratio =1.43; 95% confidence interval, 1.30-1.58) after adjustment. Traumatic brain injury was associated with insomnia compared with patients without traumatic brain injury in the multivariable model: mild/unclassified traumatic brain injury (hazard ratio = 2.07; 95% confidence interval, 1.82-2.35) and moderate/severe/ penetrating traumatic brain injury (hazard ratio = 2.43; 95% confidence interval, 2.06-2.86). Additionally, bum injury (hazard ratio =1.95; 95% confidence interval, 1.47-2.59) and amputation (hazard ratio = 1.61; 95% confidence interval, 1.26-2.06) significantly increased the risk of a diagnosis. Conclusions: Traumatic injuries significantly predicted a diagnosis of insomnia after controlling for mental health disorders. Our findings strongly suggest the need for long-term surveillance of sleep disorders in trauma survivors.