photo credit: jomilo75, “Tiger tops,” via Flickr. CC BY-NC-ND 2.0

Individuals with a rare blood type may have an increased risk of developing memory problems later in life, new research has found. According to the study, which has been published in Neurology, people with AB blood were almost twice as likely to develop cognitive impairment as individuals with other blood types.

Scientists have previously identified associations between blood type and vascular health. For example, some studies found that individuals with blood type O had a lower risk of developing heart disease and stroke, both of which can increase the risk of memory loss and dementia later in life.

Taking this one step further, researchers headed by Dr. Mary Cushman of the University of Vermont College of Medicine set out to examine the relationship between blood type and the incidence of cognitive impairment. For the study, the team analyzed data from more than 30,000 black and white adults living in the US that had previously been enrolled in a larger study called REGARDS (Reasons for Geographical and Racial Differences in Stroke).

The researchers identified 495 individuals that developed cognitive impairment during the three and a half year study. They then compared these individuals with a similar group of 587 people who had no memory problems.

They found that 6% of the individuals who developed cognitive impairment had the rare blood type AB, which is higher than the 4% found in the total US population. After adjusting for age, race, region and sex, those with AB were 82% more likely to experience problems with memory, language and attention with age when compared with other blood types. While these are often indicative of the onset of dementia, the study did not look at the risks of developing dementia.

Alongside investigating blood type, the researchers also examined the levels of a clotting protein called factor VIII. They found that those with higher levels of factor VIII in their blood also had an increased risk of developing cognitive impairment. Furthermore, average levels of this factor were higher in those with blood type AB when compared with O.

These findings are not necessarily surprising given that previous research has demonstrated that individuals with blood type AB sometimes have altered blood clotting characteristics. Moreover, Cushman’s group previously found that blood type AB was associated with a higher risk of stroke. High levels of factor VIII increases the likelihood of blood clots forming and therefore may also increase the risk of developing heart attacks or stroke.

“Our study looks at blood type and risk of cognitive impairment, but several studies have shown that factors such as high blood pressure, high cholesterol and diabetes increase the risk of cognitive impairment and dementia,” Cushman said in a news release. “Blood type is also related to other vascular conditions like stroke, so the findings highlight the connections between vascular issues and brain health.”

While this research is interesting, an association cannot prove that AB blood type is causing the increased risk of cognitive impairment. Further studies are therefore warranted.

[Via American Academy of Neurology, Neurology, CBS News and BBC News]