Objective: To evaluate the impact of staying up late (SUL) on the risk of intracranial aneurysm (IA) rupture.

Methods: This case-control study included 452 patients diagnosed with IA. They were divided into ruptured and unruptured groups. Staying up late was categorized in three levels (11-12 o'clock, 12-1 o'clock, after 1 o'clock) according to the time of falling asleep. To explore the relationship between staying up late and risk of IA rupture, univariate and multivariate logistic regression analyses were performed.

Results: Multivariate analysis found a significant difference in the percentage of patients falling asleep at 12-1 o'clock (OR, 2.25; 95% CI, 1.10-4.59) or after 1 o'clock (OR, 4.68; 95% CI, 1.74-12.55) between the ruptured and unruptured groups. The following risk factors differed significantly between the two groups: hypertension (OR, 2.05; 95% CI, 1.33–3.17), current smoking (OR, 1.72; 95% CI, 1.09–2.71), irregular IA (OR, 1.85; 95% CI, 1.15–3.00), IA size ≥8mm (OR, 1.92; 95% CI, 1.22–3.02), MCA location (OR, 2.45; 95% CI, 1.19–5.02), and aspect ratio (OR, 1.33; 95% CI, 1.02–1.73).

Conclusion: Patients who fell asleep later than 12 midnight on average showed higher risk of IA rupture. The reasons for this are not very clear. A review of the literature suggests that this association may be related to a series of physiological, pathophysiological, endocrine and metabolic changes.