Alzheimer's Gene Increases Risk Of Brain Bleeding In Men

Men with the common genetic variation, ApoE4--which is also linked to Alzheimer's disease--are at an increased risk of brain bleeding, according to a recent study.

Researchers found that men carrying the variation with mild cognitive impairment or Alzheimer's disease suffered twice as many microbleeds in their brains as women with similar diagnoses.

Microbleeds tend to differ in size and impact. For instance, while a stroke is a macro event that typically occurs on one side of the brain with an immediate effect, microbleeds occur anywhere in the brain over time with a cumulative effect.

During the study, researchers analyzed the brain scans of 658 subjects aged 48 to 91 years old in the United States and Canada who are part of the Alzheimer's disease Neuroimaging Initiative. From the sample, 402 had mild cognitive impairment, 90 had early-stage Alzheimer's disease and 166 were cognitively normal.

The ongoing study in the Karolinska Institutet Dementia Study in Sweden also analyzed the scans of 448 other subjects, aged 36 to 88 years old. Of those, 152 had mild cognitive impairment, 152 had Alzheimer's, and 144 were cognitively normal.

Now, researchers believe that the new findings show that Alzheimer's disease may be unique to humans. For instance, while humans carry three variants of ApoE4, including the most common Alzheimer's risk gene, chimpanzees, their closest relatives, only have one type of ApoE. The ApoE proteins transport cholesterol and other fats through the bloodstream.Yet even mice and apes that show some associated factors with the disease do not suffer the same cognitive impairments and neuron losses that Alzheimer's patients do; researchers believe it is because the animals do not have multiple genetic variants of ApoE. 

Previous studies have shown that ApoE4 can be an aggravating factor even for non-Alzheimer's patients and is well-known for worsening the effects of traumatic brain injuries, researchers say. 

Now, researchers are hoping to see if they can reduce microbleeds by using sex steroids as well as other changes in treatment.

"We may need different therapeutic strategies for ApoE4-carrying men who are Alzheimer's patients than for women," the researchers concluded.

The study is published in the journal Neurobiology of Aging.

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