Seasonal Variation in the Onset of Acute Cerebral Infarction and Its Association with Clinical Severity and Risk Factors: A Five-Year Single-Center Retrospective Study.

Objective: Winter low temperatures may affect the occurrence of acute cerebral infarction by affecting blood pressure, but little is known about the association between seasonal variation and the clinical severity of acute cerebral infarction. This study aims to explore the seasonal variation of acute cerebral infarction and its relationship with stroke severity and vascular risk factors. Methods: A five-year retrospective study was conducted including 692 patients with acute cerebral infarction admitted to a second class A hospital. Patients were stratified by season of onset. Stroke severity was assessed using NIHSS, and multivariable logistic regression was applied to analyze associations and interactions. Results: While incidence did not differ significantly by season, stroke severity was highest in winter. Spring onset might be independently associated with lower odds of severe stroke (OR = 0.38, 95% CI: 0.14-0.94, p = 0.05). Significant interactions were observed for alcohol use in summer (OR = 10.69, 95% CI: 1.42-222.84) and atrial fibrillation in spring (OR = 7.30, 95% CI: 1.13-66.12). Sex-stratified analysis revealed that spring onset was associated with lower incidence of moderate-to-severe stroke (NIHSS ≥ 8) among females, while atrial fibrillation and hypertension were risk factors for moderate-to-severe cerebral infarction in males. Conclusion: A seasonal variation was found in the clinical severity of acute cerebral infarction and was highest in winter. Due to the lack of direct environmental exposure data collection (such as environmental temperature, humidity, air pollution), the specific mechanism still needs further exploration.