'Silent' Strokes, Memory Loss and Alzheimer's Disease
by Joe Rojas-Burke for Oregon Live:Harmful proteins that accumulate in the brain are a hallmark of Alzheimer's disease. But researchers are starting to pay a lot of attention to another likely factor: subtle damage to blood vessels.A study out this week, for instance, found evidence that memory loss may be caused by "silent" strokes that go unnoticed but can be detected by high-resolution brain scans. As WebMD reported:
Previously, experts thought that memory loss among older adults was caused by deterioration in the hippocampus, the part of the brain involved in memory and other functions. Although that is still true, study researcher Adam Brickman, PhD, says his new research adds another possible cause to the list."What our study suggests is, even when we account for the decline in memory attributed to hippocampal shrinkage or degeneration, that strokes ... play an additional role in the memory decline," Brickman says. He is the Herbert Irving assistant professor of neuropsychology at Columbia University College of Physicians and Surgeons.
Scientists still don't know how Alzheimer's wipes out memory, scrambles the ability to think and erodes personality. Nerve cells die and the brain shrivels as the disease advances. The damage seems to begin with the clustering of protein fragments, called amyloid plaques, among brain cells. Larger tangled strands of another protein soon appear inside brain cells. Generally, the more plaques and tangles, the more severe the symptoms of dementia. 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.Some researchers, however, now believe that the field has focused too narrowly on plaque buildup, neglecting another prominent factor in the advance of Alzheimer's: widespread changes in the blood vessels that supply blood to the brain."People are coming around to the idea that maybe we've been overlooking the importance of the vascular system," says Dr. Joseph Quinn, an associate professor of neurology at Oregon Health & Science University.
At the very least, damage from blocked and disrupted blood vessels makes the brain less resistant to the onslaught of Alzheimer's disease. And improving blood vessel health may be one of the ways exercise protects the brain from the effects of aging. A Seattle-area clinical trial found that regular exercise can improve cognitive performance in older adults showing signs of mental decline:
Researchers at the University of Washington School of Medicine and Veterans Affairs Puget Sound Health Care System tested the effects of aerobic training in a clinical trial with 33 women and men diagnosed with mild cognitive impairment, often a prelude to Alzheimer's disease.Twenty-three of the volunteers, selected randomly, began an intense program of aerobic exercise, spending 45 to 60 minutes on a treadmill or stationary bike four days a week. The remaining 10, the study's control group, spent the same amount of time performing non-aerobic stretching and balance exercises.After six months, the aerobic exercisers showed significant gains in mental agility, while the non-aerobic group showed continuing decline in tests of thinking speed, fluency with words and ability to multi-task.
A study of older adults in Oregon identified mixtures of nutrients that seem to protect the brain, and other food ingredients that may worsen brain shrinkage and cognitive decline. But research to date falls short of showing that diet or exercise can stop Alzheimer's disease.
In fact, there is no convincing evidence that any nutritional supplement, herbal preparation, diet, or drug can reduce the risk of Alzheimer's disease, according to a group of independent experts convened by the National Institutes of Health in 2010. But to protect your brain, the Alzheimer's Association says it makes sense to follow the measures proven to protect the heart and blood vessels: quit smoking, exercise every day, maintain a healthy body weight, and keep cholesterol, blood pressure and blood sugar under control.
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