Aging Leads to Poor Outcome after Subarachnoid Hemorrhage through Exacerbating Early Brain Injury

Early brain injury after a subarachnoid hemorrhage is an important prognostic factor. Aging is also an important prognostic factor of subarachnoid hemorrhage. However, the association between early brain injury and aging remains unclear. Older patients have comorbidities and frailty that can affect early brain injury severity. The purpose of this retrospective study was to clarify the differences in early brain injury severity between young and older patients by adjusting for comorbidities and frailty using propensity score matching. Between 2013 and 2021, 433 patients with subarachnoid hemorrhage who presented within 72 hrs of onset were included. The patients were divided into 2 groups: those aged 18-65 years (young group) and those aged ≥75 years (older group). The primary end point was early brain injury, which comprised the clinical, radiological, and laboratory findings on admission. We used propensity score matching to adjust for histories, comorbidities, and frailty. We analyzed early brain injury in the 2 groups for both non-propensity score matching and propensity score matching cohorts. Within the non-propensity score matching cohort, 260 patients were included in the young group and 173 in the older group. The propensity score matching cohort comprised 98 patients from both groups. The older group showed a higher World Federation of Neurosurgical Societies grade (p < 0.001), higher Hijdra scale (p < 0.01), and higher proportion of acute hydrocephalus (p < 0.001) in both cohorts. The study indicated exacerbated early brain injury among older patients, with worsening neurological damage, increasing subarachnoid hemorrhage volume, and causing hydrocephalus. Clarifying the impact of aging on early brain injury may help develop therapeutic interventions for subarachnoid hemorrhage.