Why Do Certain Blood Types Have a Higher Risk of Dementia?

Researchers link blood type, brain volume, and risk of Alzheimer's disease.

Posted Jun 07, 2015

Wikimedia/Creative Commons
Source: Wikimedia/Creative Commons

Neuroscientists at the University of Sheffield have discovered that your blood type may impact gray-matter volume in brain regions linked to dementia and Alzheimer’s disease. Gray matter consists of the bulk of neurons in specific brain regions, while white matter creates communication lines between your various brain regions.

The June 2015 study, “‘O’ Blood Type is Associated with Larger Grey-Matter Volumes in the Cerebellum,” was published in Brain Research Bulletin

For this study, Matteo De Marco and Annalena Venneri calculated the volume of gray matter in various regions of the brain and correlated these statistics with blood types and risk of dementia. The researchers found that people with the 'O' blood type have more gray matter in the cerebellum (Latin for "Little Brain"), which may protect against neurodegenerative diseases such as Alzheimer's. 

Traditionally, neuroscientists have viewed the cerebellum as the seat of muscular coordination, balance, and bodily proprioception. However, new findings indicate the cerebellum is also tied to cognitive function and may fine-tune our thinking and creative processes, just as it fine-tunes our muscle movements. 

The fronto-cerebellar network connects the cerebellum to the cerebral cortex and allows for the coordination, precision, and timing of both muscle movements and thought processes. Ideally, the cerebellum allows us to move and think more efficiently.

Gray Matter Brain Volume in the Cerebellum May Have Neuroprotective Benefits

Wikimedia Commons / Life Sciences Databases
Cerebellum in red.
Source: Wikimedia Commons / Life Sciences Databases

The study found that individuals with an 'O' blood type tend to have more gray matter in the posterior portion of the cerebellum. More specifically, the ‘O’ adults had larger gray-matter volumes in two symmetrical clusters within the posterior ventral portion of the cerebellum.

Interestingly, when the researchers compared people with ‘O’ type blood to those with 'A', 'B' or 'AB' blood types they also found smaller gray matter volumes in temporal and limbic regions of the brain, including the left hippocampus. 

In 2014, researchers from Harvard Medical School reported that people over age 45 with type 'AB' blood were 82% more likely to have impaired thinking skills than those with type 'O' blood. 

The approximate distribution of blood types in the U.S. population:

  • O-positive: 38 percent.
  • O-negative: 7 percent.
  • A-positive: 34 percent.
  • A-negative: 6 percent.
  • B-positive: 9 percent.
  • B-negative: 2 percent.
  • AB-positive: 3 percent.
  • AB-negative: 1 percent.

The researchers hypothesize that the difference between blood types might be caused by the effects of 'O' blood type alleles on the brain. In a press release, De Marco said,

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

De Marco's scientific research focuses on non-pharmacological treatments that can optimize healthy aging and reduce the risks of dementia and Alzheimer’s disease. His research also aims to identify the impact of physical exercise on various neurocognitive variables. 

If you don't have 'O' blood, exercise may be a non-pharmacological treatment for increasing brain volume and optimizing cognitive function throughout your lifespan. One of the prime benefits of physical activity is that exercise stimulates the production of Irisin and BDNF (Brain-derived neurotrophic factor) which triggers the growth of new neurons (neurogenesis) throughout the brain, regardless of your blood type. 

Although the current study by De Marco and Venneri doesn't investigate the link between physical activity and dementia, other studies have found a universal correlation between aerobic fitness, BDNF, and increased gray-matter volumes.

Conclusion: "Microzones" Within the Cerebellum Have Specific Functions

Wikimedia/Creative Commons
Specific regions of the cerebellum play specific roles in cerebral processes.
Source: Wikimedia/Creative Commons

Within the cerebellum, neuroscientists continue to identify how specific cerebellar regions play a role in specific cerebral functions. The recent study from the University of Sheffield has identified clusters of gray matter within the cerebellum that may be linked to dementia and Alzheimer's disease. 

Recently, researchers at Stanford University linked the cerebellum to creativity and the creative process. The new findings from the University of Sheffield reveal cerebellar gray-matter volume as a prime candidate for further investigation of ABO function as linked to neuroprotection or degeneration of cognitive functions.  

If you'd like to read more on this topic, check out my Psychology Today blog posts:

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