Silent strokes and Alzheimer’s disease

A recent study showing that silent strokes caused memory loss received wide publicity in the media.  However the extension of that logic showing that these silent strokes therefore could be causing Alzheimer’s disease was headlined only by the Oregonian.

A hallmark of Alzheimer’s disease is that harmful proteins accumulate in the brain.  But as The Oregonian recently reported 

…treatments developed to reduce the build-up of plaques have not stopped memory loss and other symptoms from worsening. It may be that patients started treatment too late in the course of the disease, when damage is too great to reverse.

Memory loss among older adults is caused by deterioration in the hippocampus, the part of the brain involved in memory and other functions. Severe brain shrinkage can be seen in patients with advanced Alzheimer’s disease.  However a study at  the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at Columbia University Medical Center in New York suggests an additional factor.

A stroke, or cerebrovascular accident (CVA), occurs when blood supply to part of the brain is disrupted, causing brain cells to die. The study showed that 1-in-4 older adults with memory loss have had a so-called silent stroke — a small spot of dead brain cells.

Study author Adam M. Brickman had said the study involved a group of 658 people age 65 and older, free of dementia who were given magnetic resonance imaging brain scans.

Participants underwent tests that measured their memory, language, speed at processing information and visual perception. A total of 174 of the participants had silent strokes.

The study, published in the January issue of Neurology, found people with silent strokes scored somewhat worse than those without silent strokes on memory tests. This was true regardless of whether people had a small hippocampus — the memory center of the brain — the study said.

Risk factors for silent stroke include high blood pressure, obesity and high cholesterol.  Researchers are now following participants over a longer period of time to see whether some will develop Alzheimer’s.

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