Circadian modulation of surgical timing and postoperative outcomes in subarachnoid hemorrhage: a retrospective cohort analysis

BACKGROUND: Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular emergency with mortality exceeding 30%. Emerging evidence underscores the role of circadian rhythms as critical modulators of cerebrovascular pathophysiology. Building upon recent studies identifying the BMAL1 (Brain and Muscle ARNT-Like 1)-HIF2A (Hypoxia-Inducible Factor 2 Alpha) axis as a key regulator of hypoxia-driven vascular injury, this study investigates the influence of circadian timing of surgery (Time1) and disease onset (Time2) on SAH outcomes-a novel approach integrating molecular insights with clinical practice. METHODS: This retrospective study analyzed 279 patients with anterior circulation SAH admitted to the Neurointensive Care Unit (NICU) at Liaoyang Central Hospital (2018-2024). Surgical (Time1) and symptom onset (Time2) times were categorized into four 6-hour intervals. Prognostic outcomes (good/poor at 6 months) were assessed using multivariable logistic regression, validated via the Akaike Information Criterion (AIC) and residual analysis. RESULTS: Nocturnal surgery (21:00-03:00) demonstrated a non-significant trend toward reduced risk of poor prognosis (odds ratio [OR] = 0.56, P = 0.097). Onset time showed no significant association (P = 0.847). The addition of Time2 to the model increased the AIC (from 82.69 to 84.65), suggesting reduced model fit or potential overfitting. Residuals were normally distributed. CONCLUSION: Nocturnal surgery may confer neuroprotection, while onset time appears prognostically insignificant. Further mechanistic investigations are warranted.