Study looks at blood type and risk of cognitive impairment

People with blood type AB may be more likely to develop memory loss in later years than people with other blood types, according to a study published in the September 10, 2014, online issue of Neurology®, the medical journal of the American Academy of Neurology.

AB is the least common blood type, found in about 4 percent of the U.S. population. The study found that people with AB blood were 82 percent more likely to develop the thinking and memory problems that can lead to dementia than people with other blood types. Previous studies have shown that people with type O blood have a lower risk of heart disease and stroke, factors that can increase the risk of memory loss and dementia.

The study was part of a larger study (the REasons for Geographic And Racial Differences in Stroke, or REGARDS Study) of more than 30,000 people followed for an average of 3.4 years. In those who had no memory or thinking problems at the beginning, the study identified 495 participants who developed thinking and memory problems, or cognitive impairment, during the study. They were compared to 587 people with no cognitive problems.

People with AB blood type made up 6 percent of the group who developed cognitive impairment, which is higher than the 4 percent found in the population.

"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," said study author Mary Cushman, MD, MSc, of the University of Vermont College of Medicine in Burlington. "Blood type is also related to other vascular conditions like stroke, so the findings highlight the connections between vascular issues and brain health. More research is needed to confirm these results."

Researchers also looked at blood levels of factor VIII, a protein that helps blood to clot. High levels of factor VIII are related to higher risk of cognitive impairment and dementia. People in this study with higher levels of factor VIII were 24 percent more likely to develop thinking and memory problems than people with lower levels of the protein. People with AB blood had a higher average level of factor VIII than people with other blood types.