The brain is a machine that fails with age, as its component cells and structures become damaged in much the same way in all of us. At the high level of processes and larger masses of tissue the brain is complex enough to be able to fail in many, many different ways, however. Even though everyone ages in the same way at the level of cells, all it takes is a few small and consistent differences to create very different end points. For example, neurodegeneration conditions like Parkinson's and Alzheimer's disease might be thought of as the result of particular components or systems within the brain failing more rapidly in some people than in others. Everyone ages the same way, but not everyone loses enough dopamine neurons to be diagnosed with Parkinson's disease, or loses the ability to clear amyloid beta from the brain to a sufficient degree to suffer Alzheimer's disease.
Still, in part because we all age in the same way and all the varied conditions and disabilities of aging stem from the same few root forms of damage and change, some interventions can have a very broad beneficial effect. Exercise and calorie restriction are two of these, shown to produce benefits in almost every circumstance examined to date - if they were pills, the world would beat a path to the door of their manufacturer, and they would be household names. Billions of dollars are sometimes spent on commercializing therapies that do not do as well as either exercise or calorie restriction for specific groups and medical conditions.
As for many other conditions, there is a fair amount of evidence to suggest that exercise can lower the risk of neurodegeneration or slow its progression. Here are a couple of research results to illustrate the point: one association, one causation.
An active lifestyle helps preserve gray matter in the brains of older adults ... The lifestyle factors examined included recreational sports, gardening and yard work, bicycling, dancing and riding an exercise cycle. The researchers used magnetic resonance imaging (MRI) and a technique called voxel-based morphometry to model the relationships between energy output and gray matter volume.
Gray matter volume is a key marker of brain health. Larger gray matter volume means a healthier brain. Shrinking volume is seen in Alzheimer's disease. After controlling for age, head size, cognitive impairment, gender, body mass index, education, study site location and white matter disease, the researchers found a strong association between energy output and gray matter volumes in areas of the brain crucial for cognitive function. Greater caloric expenditure was related to larger gray matter volumes [and there] was a strong association between high energy output and greater gray matter volume in patients with mild cognitive impairment and AD.
People with Parkinson's disease benefit from exercise programs on stationary bicycles, with the greatest effect for those who pedal faster. ... Functional connectivity magnetic resonance imaging (fcMRI) data showed that faster pedaling led to greater connectivity in brain areas associated with motor ability.
The patients underwent bicycle exercise sessions three times a week for eight weeks. Some patients exercised at a voluntary level and others underwent forced-rate exercise, pedaling at a speed above their voluntary rate. The researchers used a modified exercise bike to induce forced-rate activity.
fcMRI was conducted before and after the eight weeks of exercise therapy and again as follow-up four weeks later. The research team calculated brain activation and connectivity levels from the fcMRI results and correlated the data with average pedaling rate. Results showed increases in task-related connectivity between the primary motor cortex and the posterior region of the brain's thalamus. Faster pedaling rate was the key factor related to these improvements, which were still evident at follow-up.
Exercise is beneficial, but that it still outperforms medical technology in any area is a sign that plenty remains to be done in the arena of research and development. Exercise cannot cure aging, and it certainly can't cure more than one or two named diseases. True longevity, additional decades of life, will only arrive from the application of near-future biotechnologies - that we can somewhat benefit from exercise is better than a poke in the eye with a sharp stick, but don't mistake taking advantage of that fact for actually getting things done.