Does Exercise Sheild the Brain from Bad Effects of Beta Amyloid?

This weeks edition of ALZForum carried an interesting article regarding the effects of exercise protecting the brain from neurodegenerative disease.  The article reported information presented at the recent Alzheimer's Association International Conference in Los Angeles.  It cited several studies of exercise and brain health.  These included a large, important study (7,800 participants, 50 yrs and older -- part of "The English Longitudinal Study of Ageing") that found after 12 years, exercise reduced the risk of dementia by 40%.  The article was "Physical Activity May Shield the Brain from the Onslaught of Aβ."

What was specifically interesting about the information was that it made a differentiation of positive effects on brain health of exercise and positive effects of a healthy cardiovascular system.

Neurologists and researchers are fond of saying "what's good for the heart is good for the brain," and so it is.  Autopsies of the brains of people who had displayed evidence of dementia often find the plaques and tangles that signal AD, but too often they also find evidence of coexisting cardiovascular disease capable of having produced the dementia.  We usually refer to this as mixed dementia.  

As we discuss in Beating the Dementia Monster, the article acknowledges that physical exercise aids brain health by promoting generation of the brain-derived neurotrophic factor (BDNF) protein, but it also promotes a healthy cardiovascular system.  This makes it difficult to determine the relative effectiveness of physical exercise and maintaining good cardiovascular health on brain health.  The article acknowledged this difficulty, but concludes the effects are approximately equal.

We have discussed before the ambiguity in the amyloid hypothesis -- while the presence of plaques typifies AD, it's not clear what the role of amyloid is and if removing it will affect the progress of the disease.  The article noted few studies have examined how physical activity modulates the relationships between Aβ deposition, brain volume, and cognitive decline.  But the article highlights one study that is helpful here.  It is the Harvard Aging Brain Study (HABS), which followed 182 cognitively normal participants who averaged 73 years of age at baseline.  The outcome was that, for subjects with amyloid deposition in their brains, physical activity was strongly correlated with less cognitive decline and brain atrophy.  

I don't know how much amyloid I have deposited in my brain.  I had a lumbar puncture ("spinal tap") for the insulin study, but (consistent with their protocol) they never shared the results with me.  This was likely done to measure beta amyloid in my cerebrospinal fluid.  The way to do that now would be a PET scan targeting beta-amyloid, but the insurance company would never pay for it.  If I wanted to pay out-of-pocket, the cost would likely be over $5,000.  My guess is that I have a lot, but, consistent with this study, physical exercise has significantly impeded the advance of dementia.  Every morning when I wake up I am so grateful for this!