Could your blood type put you at increased risk for dementia? A pioneering new study by researchers at the University of Sheffield suggests the answer is yes.

The study, published in the Brain Research Bulletin, indicates people with an “O” blood type have more grey matter in their brain, which helps to protect against diseases such as Alzheimer's, than those with “A,” “B,” or “AB” blood types, Medical Xpress reports.

The reason: Blood types play a role in the development of the nervous system and may cause a higher risk of developing cognitive declines.

Matteo De Marco and Professor Annalena Venneri, from the University's Department of Neuroscience, made the discovery after analyzing 189 Magnetic Resonance Imaging (MRI) scans from healthy volunteers. They calculated the volumes of grey matter within the brain and explored the differences between different blood types.

The results showed individuals with an “O” blood type have more grey matter in the posterior proportion of the cerebellum. Those with other blood types had smaller grey matter volumes in temporal and limbic regions of the brain — including the left hippocampus, which is a part of the brain damaged by Alzheimer's disease.

"The findings seem to indicate that people who have an 'O' blood type are more protected against the diseases in which volumetric reduction is seen in temporal and mediotemporal regions of the brain like with Alzheimer's disease for instance," said Matteo DeMarco.

"However additional tests and further research are required as other biological mechanisms might be involved."