Insomnia prevalence among U.S. Army soldiers with history of TBI.

The study was cross-sectional, so it cannot show that TBI caused insomnia or that insomnia followed the injury. TBI history was based on self-reported answers about head, neck, or blast injury, loss of consciousness, and memory problems, not medical diagnoses or neurodiagnostic findings. 16.6% did not answer the TBI questions and were excluded, and survey completion was not mandatory, so findings may not apply to all soldiers. The questionnaire asked about lifetime injury history but not when injuries occurred, so timing relative to current sleep symptoms is unknown. Insomnia was measured with self-report only; no sleep diary, actigraphy, or polysomnography was available. The insomnia definition required symptoms in 3 months out of the past year, not the consecutive 3 months specified in DSM-5. The analysis did not account for possible influences such as anxiety, depression, posttraumatic stress, substance use, chronic pain, or psychosocial functioning.

Do not read the higher insomnia rate in the moderate to severe TBI group as evidence that brain injury caused the sleep problem. The study measured self-reported lifetime TBI and current insomnia symptoms at one time point, without injury timing or medical confirmation, so it cannot establish cause.