When we think of Alzheimer disease, many understand that this is a disease of ongoing, progressive deterioration in thinking. Simply put, our thinking ability and problem solving – cognitive function- and our memory declines. But it is also associated with other features such as depression and impaired gait.
In fact, early studies now suggest that this kind of non-brain signs, if you will, may be early signs of Alzheimer’s. In this week’s Archives of Neurology is a study that asks if muscle strength is in some way related to Alzheimer’s.
It is known that BMI and physical activity are related to the risk of AD but it is not clear if muscle strength has an independent relation to Alzheimer’s.
The authors looked at 900 dementia-free people and at nine different muscle groups in the arms and legs as well as strength through the body core.
The participants were followed for close to four years and by then, 24% had developed Alzheimer’s. Those who did develop dementia were found to be older, had lower cognitive function and showed decreased strength in several muscles compared to those participants who did not develop Alzheimer’s. In fact, each 1-U increase in muscle strength was associated with a 43% decrease in the risk of Alzheimer’s. Participants with the higher level of muscle strength (90th percentile) had a 61% decrease of developing Alzheimer’s.
In addition the authors looked at the development of a precursor to AD called MCI (mild cognitive impairment) and found that of the 275 who developed MCI, those with muscle strength in the 90 percentile had a 48% decrease of developing MCI. It also was interesting that those with greater muscle strength had a slower rate of decline as well.
It would seem that there might be a common cause that underlies both muscle loss and cognition in aging.
So the question then is — is loss of muscle strength a risk factor for Alzheimer’s or is there some common reason that muscle strength declines and Alzheimer’s starts?
It has been suggested that our energy-making cells (called mitochondria) might get damaged over time. The energy factories are often located in muscles and the damaged factories might lead to decreased strength and other signs of aging. It might be possible that stroke or mini strokes could lead to weakness of the muscles and unmask AD.
So what does this mean in a practical way? It is entirely possible that maintaining muscle strength through exercise and a healthy lifestyle could be one more way to reduce your risk of cognitive decline and dementia.
These observations support the view that exercise has a beneficial effect of reducing the risk of developing significant cognitive loss and dementia. Yet one more reason to keep moving!