(HealthDay News) – Over 60% of women have male DNA in their brains, possibly from a prior pregnancy with a male fetus, which is associated with a lower prevalence of Alzheimer’s disease, according to a study published online Sept 26 in PLoS One.

William F.N. Chan, PhD, from the Fred Hutchinson Cancer Research Center in Seattle, and colleagues quantified male DNA (via the Y-chromosome-specific DYS14 gene) in the brain autopsies of 59 women who had died from 32–101 years of age. Of these, 26 had no evidence of neurologic disease and 33 had Alzheimer’s disease.

The researchers found that 63% of the women had male DNA in the brain. Male DNA was found in multiple brain regions and throughout life, with a 94-year-old woman being the oldest found to harbor male DNA. Women with Alzheimer’s disease had significantly lower prevalence (P=0.03) and concentration (P=0.06) of male microchimerism.

“In conclusion, male microchimerism is frequent and widely distributed in the human female brain,” Chan and colleagues write. “Although the relationship between brain microchimerism and health versus disease requires further study, our findings suggest that microchimerism of fetal origin could impact maternal health and potentially be of evolutionary significance.”

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