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This study examines how the time of acute ischemic stroke onset affects the severity of symptoms at admission.

February 13, 2026Open Access

The Influence of Circadian Onset Time on Admission Severity in Acute Ischemic Stroke: A Retrospective Cohort Study

Key Points

This study examines how the time of acute ischemic stroke onset affects the severity of symptoms at admission.
Conducted a multicenter retrospective cohort study across 36 hospitals in Shenzhen, China.
Included 14,048 patients diagnosed with acute ischemic stroke between January 2022 and May 2024.
Classified stroke onset time into Morning, Afternoon, Evening, and Night periods.
Measured admission severity using the NIHSS score and mRS score.
Employed multivariable ordinal logistic and linear regression models for analysis.
Morning onset associated with lower NIHSS scores (aOR = 0.88; P < .001) and lower mRS scores (aOR = 0.81; P < .001).
Night onset linked to higher NIHSS scores (aOR = 1.20; P < .001) and higher mRS scores (aOR = 1.25; P < .001).
The associations remained consistent across various clinical subgroups but weakened in certain conditions like coronary artery disease.

Abstract

Background Stroke onset demonstrates a circadian pattern, but the relationship between onset time and stroke severity at admission remains insufficiently understood. Objectives This study aimed to examine the association between time of stroke onset and admission severity in patients with acute ischemic stroke (AIS), and to determine whether this association varies across clinical subgroups. Design A retrospective observational study. Methods We conducted a multicenter retrospective cohort study including 14,048 patients diagnosed with AIS and admitted to 36 hospitals in Shenzhen, China, between January 1, 2022, and May 31, 2024. Stroke onset time was classified into 4 periods: Morning (05:00-10:59), Afternoon (11:00-16:59), Evening (17:00-22:59), and Night (23:00-04:59). The primary outcome was neurological severity at admission, measured by the NIHSS score. Associations between onset time and outcomes were evaluated using multivariable ordinal logistic and linear regression models, adjusted for demographic and clinical covariates. Subgroup analyses and sensitivity analyses using multiple imputation were also conducted. Results Stroke onset in the Morning was associated with lower NIHSS scores (adjusted odds ratio aOR = 0.88; 95% confidence interval CI: 0.82-0.94; P < .001) and lower mRS scores (aOR = 0.81; 95% CI: 0.76-0.86; P < .001). In contrast, Night onset was associated with higher NIHSS scores (aOR = 1.20; 95% CI: 1.09-1.32; P < .001) and mRS scores (aOR = 1.25; 95% CI: 1.15-1.37; P < .001). These associations were consistent across strata defined by age and sex, and among patients with hypertension or diabetes. However, the circadian pattern was attenuated in patients with coronary artery disease, dyslipidemia, or atrial fibrillation. Conclusion Admission stroke severity follows a circadian pattern, with milder presentations in the Morning and more severe impairments during Night hours. These findings highlight the potential role of circadian biology in stroke pathophysiology and support incorporating time-of-onset considerations into clinical risk stratification and acute management strategies.

The Influence of Circadian Onset Time on Admission Severity in Acute Ischemic Stroke: A Retrospective Cohort Study

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