Abstract TP43: Circadian Variation In Stroke Onset On Weekdays Compared With Weekends/Holidays

Abstract

Background: Ischemic and hemorrhagic stroke onset exhibit is known to exhibit diurnal variation throughout the 24-hour cycle. But whether this variation differs on weekdays compared with weekends/holidays has not been well delineated. Methods: We evaluated consecutive patients with acute cerebral ischemia [(ACI), including ischemic stroke (IS) and transient ischemic attack (TIA)] and intraparenchymal hemorrhage (IPH) enrolled during ambulance transport to 60 receiving stroke centers in the NIH FAST-MAG trial. Enrollment required onset within the prior 2 hours, excluding confounding by wake-up and unwitnessed onset strokes. The patterns of time of onset were analyzed: 1) hourly, 2) in 4-hour increments, and 3) daytime (08:00-19:59) vs. night-time (20:00-07:59). Diurnal variation in presenting demographic/clinical features were assessed using ANOVA, Kruskal-Wallis, t-tests, and Wilcoxon Rank-Sum. Results: Among 1615 patients (1202 enrolled on weekdays and 442 on weekends/holidays), 64% had IS, 12.5% TIA, and 23.5% IPH. ACI patients had different patterns of onset time (Figure). During weekdays, a broad plateau of highest rates of onset occurred 09:00-22:00. Conversely, during weekends/holidays, a unimodal peak was observed between 14:00-16:00. In contrast, patterns of onset time in IPH patients were broadly similar, with bimodal peaks on both weekdays and weekends/holidays. However, the first peak occurred earlier on weekdays (09:00-12:00 vs. 11:00-13:00), with the second peak occurring within 17:00-20:00 in both groups. Conclusion: Acute cerebral ischemia shows marked, and intraparenchymal hemorrhage minor, pattern differences in onset times on weekdays vs. weekends/holidays, likely related to variations in times of greater physical activity and stress. These findings can inform EMS resource allocation to stroke, aligned with weekday vs. weekend/holiday onset patterns.