Author: Samantha Lefebvre
Institution: Queen's University
Could exercise be the key to helping prevent dementia as we age? This question was explored by a longitudinal study at UCLA, where researchers studied the impact of physical activity on dementia. Their findings support that there is an inverse relationship between physical activity levels and cognitive decline.
In Physical activity, brain volume, and dementia risk: the Framingham study, researchers followed older individuals affiliated with the ground-breaking Framingham study. The 1948 Framingham study was one of the first studies to extensively track common risk factors for a disorder in individuals unaffected by the disease. The team of UCLA scientists applied the Framingham method to dementia, studying whether there is a link between risk of dementia, subclinical brain markers for dementia, and physical activity. Members of the original Framingham cohort, as well as their offspring, were selected for this study if they were over 60 years of age and cognitively sound. These participants were not afflicted with dementia; this allowed researchers to measure risk of dementia in relation to physical activity levels. Additionally, the research group examined the association between brain MRIs and physical activity in over 2000 offspring of original Framingham participants.
After over a decade of follow-ups, the UCLA researchers came to a compelling conclusion – there is an association between increased risk of dementia and lower levels of physical activity. Individuals with lower levels of physical activity had higher risk of dementia, and both genetic and environmental factors were considered in order to arrive at this conclusion.
The relationship between dementia and physical activity only applied to those over 75 years of age who were non-carriers of the APO ε4 allele. The APO ε4 allele is implicated in the formation of protein plaques in the brain that contribute to dementia; this finding suggests that the measured increase in risk cannot largely be attributed to genetic factors. Instead, what contributed to an increase in risk of dementia was an environmental factor: of lack of exercise due to a sedentary lifestyle.
Interestingly, this lack of physical activity was shown to be linked to a decrease in both total brain and hippocampal volumes. Though not much is known yet about the mechanism of brain volume changes, these volume decreases threaten the integrity of brain tissue and cognitive function. In a 2006 review, Ruth Peter explains that changes in brain volume can stem from neuronal cell death. Change in brain volume can alter the morphology of the dendritic spines and even the synapses of neurons, which are important for neurotransmission. If neurotransmission is affected in the hippocampus, which is responsible for the formation and retention of memories, it could disrupt normal cognition and explain the pathophysiology of dementia. Thus, a sedentary lifestyle puts the hippocampus at risk for shrinkage, which affects neurotransmission and can contribute to dementia.
Though these results are compelling, what is of even greater interest are the clinical implications of this study. How can these results help create a brighter future, one where millions are saved from dementia? The answer could lie with changes in geriatric care, and most importantly, utilizing “exercise prescriptions” as a preventative measure against cognitive decline. One benefit from this research could be changes in occupational therapy and care for the elderly. Introducing mild physical activity into the daily care of elderly patients or those afflicted with dementia could make all the difference. If health care providers were to encourage movement in their patients, even if they have dementia or are significantly at risk, it could help lessen or delay the onset of disease.
Though ‘prescribing’ physical activity for those at risk of, or already suffering from, dementia may help alleviate the severity of the disease, one could also assume that the benefits may be significantfor individuals who are younger and not yet at risk. Operating upon the principles of preventative medicine, the primary health care team can and should promote physical activity. Initiating this routine earlier on in life could help maintain the volume of these vital brain structures, while simultaneously providing many other health benefits. Patients need to know that there are many rewards to be reaped from a fitness regime that not only will protect their bodies, but also their minds.
There is still much work to be done to understand the relationship between physical activity levels and cognitive decline. This research has shown that genetics may not be the primary determinant in risk of dementia, and that physical activity plays more of an intrinsic, biochemical role in dementia onset than scientists have previously assumed. Further research will hopefully focus on the mechanisms underlying this relationship, allowing dementia patients to reap both the physical and mental benefits of exercise. Time to dust off those running shoes and get active!
SOURCES
http://neurosciencenews.com/exercise-dementia-brain-size-4767/
http://biomedgerontology.oxfordjournals.org/content/early/2016/07/15/gerona.glw130
http://alzdiscovery.org/cognitive-vitality/what-apoe-means-for-your-health
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2596698/