Sex and age effects on risk of non-traumatic subarachnoid hemorrhage: Retrospective cohort study of 124,234 cases using electronic health records

Objectives: The epidemiology of non-traumatic subarachnoid hemorrhage (SAH) is unclear. This study describes the antecedent characteristics of SAH patients, com-pares the risk of SAH between women and men, and explores if this changes with age. Materials and methods: Retrospective cohort study using an electronic health records network based in the USA (TriNetX). All patients aged 18-90y with at least one healthcare visit were included. Antecedent characteristics of SAH patients (ICD-10 code I60) were measured. The incidence proportion and the relative risk between women and men, were estimated overall, in the 55-90y age group, and in five-year age categories. Results: Of 58.9 million eligible patients, with 190.8 million person-years of observations, 124,234 (0.21%; 63,467 female, 60,671 male) had a first SAH, with a mean age of 56.8 (S.D. 16.8) y (women: 58.2 [16.2] y, men 55.3 [17.2] y). 9,758 SAH cases (7.8%) occurred in people aged 18-30y. Prior to the SAH, an intra-cranial aneurysm had been diagnosed in 4.1% (women: 5.8% men: 2.5%), hyperten-sion in 25.1% and nicotine dependence in 9.1%. Overall, women had a lower risk of SAH compared to men (RR 0.83, 95% CI 0.83-0.84), with a progressive increase in risk ratio across age groups: from RR 0.36 (0.35-0.37) in people aged 18-24y, to RR 1.07 (1.01-1.13) aged 85-90y. Conclusions: Men are at greater risk of SAH than women overall, driven by younger adult age groups. Women are at greater risk than men only in the over 75-year age groups. The excess of SAH in young men merits investigation.

Automated summary

This study examines the antecedent characteristics of non-traumatic subarachnoid hemorrhage (SAH) patients, compares the risk of SAH between women and men, and investigates if this changes with age. The results show that men have a higher risk of SAH than women overall, particularly in younger adults. However, in the age group over 75 years, women have a higher risk of SAH compared to men.