Abstract A067: Diurnal Variation in Acute Ischemic Stroke Severity and Outcomes: Insights from the Get With The Guidelines Registry

Background: Preclinical models demonstrate circadian biology influences ischemic brain injury with accelerated infarct growth during the inactive phase. Whether this translates to humans is unclear. We analyzed the national US Get With the Guidelines (GWTG) – Stroke registry to assess diurnal (time-of-day) variations in AIS onset and patient outcomes. Methods: We identified all 2015-2023 AIS discharges from GWTG – Stroke hospitals. Multivariable mixed-effect logistic regression and univariable sinusoidal regression analyses were used to determine the associations between AIS onset time and discharge outcomes [global disability (mRS), ambulatory status, discharge destination, mortality]. We adjusted for 30 patient-level variables: demographics, medical history, AIS factors, 6 hospital-level variables. AIS onset time was analyzed as dichotomous [daytime (07:00-22:59) vs nighttime (23:00-06:59)]; in six 4-hour blocks; and as a continuous variable. Results: Among 1,398,777 patients from 2,593 hospitals, median age was 71 (IQR 61-81), 48.8% were women, mean presenting NIHSS was 6.4 (±7.2), and 24.54% received IV thrombolysis. AIS incidence varied nearly 3-fold by time-of-day with a peak in the late morning to early afternoon (09:00-13:00) (Fig 1). Presenting NIHSS varied modestly with onset time, with a mean of 6.1 in the morning (07:00-10:59) to 6.6 in the late evening (19:00-22:59) ( p