Sex comparison of total cerebral and intracranial arterial cerebrovascular reactivity

Background: Cerebrovascular reactivity (CVR) is the control of cerebral blood flow in response to specific stressors such as carbon dioxide (hypercapnia). CVR is associated with cerebrovascular diseases and lower CVR affects the progression and likelihood of stroke and dementia/Alzheimer’s disease. CVR exhibits sex-specific patterns which could be due to the role of biological sex or sex hormones. Previous studies have shown a decrease in CVR after menopause in women, while evidence of acute changes in CVR across the menstrual cycle remain unclear. Past investigations of sex differences in CVR have been highly variable and have not controlled for confounding variables. The purpose of this study was to determine if there is any CVR differences between young, healthy adults. We hypothesized that males will display greater CVR than females for total blood flow and individual intracranial vessels. Methods: CVR was measured in 37 young, healthy adults (14F) using phase contrast vastly undersampled isotropic projection reconstruction magnetic resonance imaging (PC-VIPR MRI). Females were tested during the early follicular phase of the menstrual cycle. Subjects underwent two MRI study visits and CVR was calculated at the %ΔCBF/ΔETCO2 (%mmHg) for total CBF and individual cerebral arteries. Statistical analysis was performed with a two-way ANOVA to compare sex differences in CVR and intrasex-vessel differences. Results: Whole brain CVR (%mmHg) was 3.3 ± 1.4 for females and 3.4 ± 1.8 for males (p=0.728). The CVR (%mmHg) ranged between 1.2 ± 2.0 in the middle cerebral artery (MCA) and 4.1 ± 2.2 in the vertebral artery for females. For males, CVR (%mmHg) ranged from 1.7 ± 2.1 in the MCA and 3.7 ± 2.2 in the anterior cerebral artery, but no arteries showed significant differences in CVR between sex. Further, no differences were found between arteries (p >0.141). The right vertebral artery showed a trend for greater CVR in females (p=0.051). Conclusion: Contrary to our hypothesis, our findings do not support that males would exhibit greater CVR than females. It is possible that sex differences were removed after the strict control of confounding variables. Future studies should investigate sex differences in CVR with increased sample sizes and hormonal manipulation to isolate those effects. Funding: NIH RO1 HL 150361 This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.