women's brains
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Although the jury is still out on what exactly causes gender differences, it’s safe to say that there are biological differences between people assigned male at birth and people assigned female at birth. And there are still plenty of new differences to discover. For instance, a new study has found that women’s brains appear younger than men’s at the same age.

In the study, published on February 4th in Proceedings of the National Academy of Sciences of the United States of America, researchers compared the “metabolic brain ages” of 205 neurologically typical adults between the ages of 20 and 82. The subjects self-identified as either male or female. To determine a brain’s “metabolic age,” the scientists used PET imaging to measure blood flow, oxygen consumption, and the use of glucose. Manu Goyal, assistant professor of radiology and neurology at Washington University in St. Louis and the study’s lead author, told CNN that they then used “machine learning” to estimate the subjects’ ages based on the measurements—which had some surprising results.

The study notes that the researchers performed the calculations six times to reach their conclusions. At first, they “trained” the machines to estimate age based only on male brains, which resulted in female brains’ “metabolic ages” being an average of 3.8 years younger than male brains. Then, they “trained” the machines using only female brains and found that male brains’ metabolic ages were about 2.4 years older than female brains.

So, what exactly does this mean?

Some scientists think that having a higher brain metabolism can protect against neurodegenerative diseases like Alzheimer’s. Roberta Diaz Brinton, who directs the Center for Innovation in Brain Science at the University of Arizona Health Sciences, told NPR that for this reason, the study was “great news for women.” But she noted that menopause can cause brain metabolism to drop more severely in some women, leaving them more vulnerable to Alzheimer’s.

In the study, Goyal and the other researchers noted that they didn’t have enough data to evaluate the effect of menopause on women’s metabolic brain age, although the sex-based differences they found were present even in subjects older than 60. They also pointed out that the effect that gender has on the development of diseases isn’t necessarily straightforward and that this connection “warrants further investigation.”

Overall, it’s still not clear what the implications of these findings are—but we’re hoping to find out.