Scientists from the University of Sheffield in Britain have identified a factor that may reduce one’s risk of suffering from Alzheimer’s.

What did the study find?
Researchers believe that people with an ‘O’ blood type may be shielded from the disease as they have larger grey-matter volumes in two symmetrical clusters within the posterior ventral portion of the cerebellum when compared to people with ‘A’, ‘B’ or ‘AB’ blood types. Additionally, non-‘O’ adults showed lower volume values in temporal and limbic regions, including the left hippocampus. Although their study seems to suggest that having an ‘O’ blood type might play a role in protection against those conditions in which temporal and mediotemporal volumetric loss is observed (Alzheimer’s disease), additional supporting evidence is needed.

How are blood types and Alzheimer’s related?
According to the findings of the study, blood types play a role in the development of the nervous system and may increase the risk of cognitive decline. With increasing age, grey matter in the brain reduces and as we age this difference in grey matter between blood types is likely to intensify.
Matteo de Marco, one of the researchers said that people with an ‘O’ blood type are more protected against diseases in which there is a volumetric reduction in temporal and medial temporal regions of the brain, similar to Alzheimer’s. Read about the 10 foods that halve the risk of Alzheimer’s.

How was the study conducted?
They analysed 189 MRI scans from healthy volunteers and studied the volume of grey matter in the brain and how it varies with different blood types.

What did the study conclude?
It was found that people with ‘O’ blood group had more grey matter in the posterior portion of their cerebellum. Whereas, people with other blood groups had smaller grey matter volumes in temporal and limbic regions of the brain including the left hippocampus, the part that is damaged early during Alzheimer’s

Read about the symptoms and diagnosis of Alzheimer’s disease.

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Abstract

Recent evidence indicated higher incidence of cognitive deficits in ABO blood-type system ‘AB’ individuals. Since this statistical difference might originate from the lack of protective effects exerted by ‘O’ alleles on the brain via vascular or non-vascular routes, this study investigated volumetric differences in grey matter between ‘O’ and non-‘O’ adults to explore the possibility of a structural endophenotype visible in ‘O’ adults without cognitive impairment or neurodegeneration.

A large sample of cognitively healthy adults who had previously undergone structural MRI for research purposes were contacted telephonically and enquired about their ABO blood type. Out of the 189 individuals who were able to retrieve and communicate this information, ‘O’ (n = 76) and ‘A’ adults (n = 65) were included in Model 1. In Model 2, all non-‘O’ (n = 113) were instead collapsed in a single group. Voxel-Based Morphometry analyses were carried out on three-dimensional T1-weighted scans, and between-sample t tests were run to compare the maps of grey-matter volumes of the subgroups of interest, controlling for major nuisance variables.

In Model 1, ‘O’ adults had larger grey-matter volumes in two symmetrical clusters within the posterior ventral portion of the cerebellum. This was confirmed in Model 2. Additionally, non-‘O’ adults showed lower volume values in temporal and limbic regions, including the left hippocampus.

The cerebellar clusters were located in regions previously found to be part of a network responsible for sensorimotor integration. It is speculated that the structural reductions seen in non-‘O’ adults might result in a susceptibility to down-regulation of this network. This occurrence is likely to intensify along the ageing process and may contribute to foster cognitive decline. Although Model 2 seems to suggest that having a ‘O’ blood type might play a role in protection against those conditions in which temporal and mediotemporal volumetric loss is observed (Alzheimer’s disease), additional supporting evidence is needed.

A number of potential biological processes might sustain these between-group differences, including sensorimotor ontogenesis, hormonal function, and a regional impact of cerebral amyloid angiopathy. These findings identify the cerebellar tissue as a candidate for further studying ABO function, and support a general association between ABO blood type and variance in the development of the nervous system.

The study was published in the journal The Brain Research Bulletin in July 2015.