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

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.

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).

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.