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

## TL;DR

This study explores how the timing of surgery and symptom onset affects outcomes in subarachnoid hemorrhage patients, suggesting nocturnal surgery may offer benefits.

## Contribution

The study introduces a novel integration of circadian timing with molecular insights to evaluate surgical and onset time effects on SAH outcomes.

## Key findings

- Nocturnal surgery showed a non-significant trend toward reduced risk of poor prognosis.
- Symptom onset time had no significant association with prognosis.
- Adding onset time to the model reduced model fit, suggesting potential overfitting.

## Abstract

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.

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.

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.

Nocturnal surgery may confer neuroprotection, while onset time appears prognostically insignificant. Further mechanistic investigations are warranted.