Sex Differences in Neurological Outcome at 6 and 12 Months Following Severe Traumatic Brain Injury. An Observational Analysis of the OXY-TC Trial.

The effect of sex in outcomes after severe traumatic brain injury (TBI) remains uncertain. We explored whether outcomes differed between women and men after standardized care management during the first 5 days in the intensive care unit (ICU). This study was an observational analysis of the OXY-TC multicenter randomized clinical trial between June 15, 2016 and April 17, 2021. Recruited patients had a pre-hospital Glasgow Coma Scale (GCS) score of 3-8, mechanical ventilation, and intracranial pressure (ICP) with or without brain tissue oxygen pressure (PbtO₂) monitoring. Objectives were to maintain ICP at 20 mmHg or below and PbtO2 above 20 mmHg at all times. The primary end-point was the proportion of women and men with poor outcomes at 6 months, corresponding to an extended Glasgow Outcome Scale (GOSE) score of 1-4 (death to upper severe disability). Of 318 randomized patients, 200 men and 71 women were analyzed. They were comparable in age, comorbidities, and initial injury severity scores. However, women had larger doses of ICP as the proportion of monitoring time of ICP above 20 mmHg 8% (3-18; median, interquartile range) versus 3% (1-10), respectively (p = 0.002). They required more often at least one tier-3 treatment, i.e., barbiturate coma and therapeutic hypothermia, for refractory intracranial hypertension during the first 5 days in the ICU: 33/68 (48%) versus 60/193 (31%), respectively (p = 0.012). At 6 months, the proportion of women with GOSE 1-4 was significantly higher than men: 48/71 (68%) versus 94/200 (47%), respectively (odds ratio 2.35 [1.33-4.16]; p = 0.003]. Similar differences were found using Disability Rating Scale and Functional Independence Measure at 6 and 12 months, and GOSE at 12 months. Sex differences in neurological outcomes persisted after adjustment for other determinants of outcome such as age, initial GCS score, and dose of ICP during the 5-day monitoring. In conclusion, women sustained more severe ICP and required more active treatment, both of which would explain a worse outcome after severe TBI. Prospective research is required to confirm these findings and identify possible mechanisms. Trial registration: ClinicalTrials.gov Identifier NCT02754063 (April 28, 2016).