Male DNA in women’s brains could protect against Alzheimer’s

Researchers found that up to two thirds of women carry male DNA in their brain, which was most likely passed on to them while pregnant with sons.

The exact medical consequences of the transfer from foetus to mother remains unclear but a study showed it was less common in women who suffered from Alzheimer’s, suggesting that it could offer protection against the condition.

Previous studies insicate that similar processes of DNA transfer could raise the risk of some cancers, such as breast cancer, and lower the risk of others including cancer of the colon.

The new study of brain tissue taken from 59 women who died aged 32 to 101 found male DNA in 63 per cent of specimens.

The findings, published in the Public Library of Science ONE journal, also showed that the male DNA was less common in the parts of the brain most severely damaged by Alzheimer’s.

But the researchers, from the Fred Hutchinson Cancer Research Centre in Seattle, emphsaised that the small scale of the study and the lack of data on the women’s pregnancy history meant the evidence was not conclusive.

Dr William Chan, who led the project, said: “Currently, the biological significance of harbouring male DNA and male cells in the human brain requires further investigation.”