Time-of-day variation affects onset but not hematoma size in intracerebral hemorrhage.

Introduction: In acute ischemic stroke, the time of day has been shown to influence the progression of the ischemic core, ultimately impacting patient outcomes. For intracerebral hemorrhage (ICH), data on such an impact on ICH severity are conflicting. Our aim was to identify possible associations between the timing of ICH onset and radiographic and clinical characteristics. Methods: We conducted a retrospective monocentric study on 381 adult patients with spontaneous ICH who were treated between 2010 and 2024. Patients were categorized by time of symptom onset (morning: 5:00 AM-10:59 AM, midday: 11:00 AM-4:59 PM, evening: 5:00 PM-22:59 PM and night: 23:00 PM-4:59 AM). Primary outcome was ICH volume at the first imaging scan. Secondary outcomes included edema volume, mortality, the presenting syndrome severity and Modified Rankin Scale (mRS) at discharge. Results: Intracerebral hemorrhage (ICH) onset exhibited a distinct distribution, with peaks around noon and afternoon (~4 PM), and the lowest frequency during nighttime. ICH and edema volumes, mortality, initial clinical severity, and functional outcomes did not differ significantly between onset-time groups. Independent predictors of mortality included age (OR 1.04, 95% CI 1.01-1.07, Conclusion: In our cohort, ICH onset times peaked during the daytime, however initial ICH and perifocal edema volumes did not differ according to the time of day. Among patients with witnessed and precisely documented ICH onset, early survival and short-term functional outcomes in patients treated at a university hospital with 24-h neurosurgical availability appear to be more strongly influenced by individual patient characteristics such as age and pre-existing conditions than by the timing of symptom onset.