Impact of Premorbid Function and Comorbidities in Geriatric Traumatic Brain Injury Patients: A Systematic Review

Population aging is increasing geriatric traumatic brain injury (TBI), with outcomes depending on premorbid health beyond chronological age. This systematic review examined how premorbid functional status, frailty, and comorbidities influence mortality, functional recovery, and other outcomes in adults aged ≥60 years with TBI. Following the PRISMA 2020 statement, PubMed, Scopus, Web of Science, and Google Scholar were searched (2016-2026). Twenty observational studies (n = 128,793) were included. Narrative synthesis was performed; risk of bias was assessed with Joanna Briggs Institute tools. Frailty (Clinical Frailty Scale, Fatigue, Resistance, Ambulation, Illness, and Loss of weight (FRAIL) Scale, and Hospital Frailty Risk Score) and premorbid ADL dependence consistently predicted higher mortality, unfavorable Glasgow Outcome Scale-Extended scores, prolonged hospitalization, and adverse discharge disposition. Comorbidities (diabetes, chronic kidney disease, and cardiovascular disease) independently worsened neurological recovery and increased complications. Frailty measures provided prognostic value superior to age alone after adjustment for injury severity. In conclusion, premorbid functional status, frailty, and comorbidities are key determinants of outcome in geriatric TBI. Routine frailty and comorbidity assessment should be integrated into clinical evaluation and prognostic models to improve risk stratification and guide individualized management.