Female mouse brains extracted a smaller share of blood oxygen
In a laboratory experiment, 15-month-old female mice had higher blood flow in the brain’s outer layer than males, without a deficit in oxygen delivery through arteries.
Limit: Oxygen measurements were inside blood vessels, not directly in brain tissue
Edited by Boris Djordjevic · AgingResearch.News
Researchers studied 15-month-old female and male mice in a laboratory experiment. They used microscopy and measurements of oxygen inside blood vessels to study capillaries, the brain’s smallest blood vessels.
Females had higher blood flow in the cortex, the brain’s outer layer, but extracted a smaller fraction of oxygen from blood, without a deficit in oxygen delivered through arteries. Variation in the time blood took to pass through capillaries increased more steeply with average passage time in females. Estrogen levels and blood-vessel diameters on the brain’s surface did not differ between sexes. Differences in gene activity were most prominent in white matter, tissue containing nerve fibers.
Why it matters
Sex differences in brain aging raise questions about how blood vessels support aging tissue. The findings suggest that studying these differences requires attention to the smallest vessels and regional tissue biology, not total brain blood flow alone.
Caveats
The comparison did not establish that higher blood flow caused lower oxygen extraction. The findings concern mice, not people, and the preprint has not been peer-reviewed.
- Immune response
- Inflammation
- Sex hormone signaling (estrogen, androgen)
- Estrogens
- Arterial oxygen delivery
- Mice
The paper
Sex shapes capillary flows and oxygen extraction in the middle-aged mouse brain
Aarhus University
bioRxiv, Oct 18, 2026, Open access, CC BY-NC-ND, Preprint, not peer-reviewed
