It is no secret that physical activity can reduce the risk of cognitive decline due to both normal aging and dementia [1–3]. Being active enhances metabolic, structural, and functional elements of the brain, thereby improving cognition [4]. At the recent Alzheimer’s Association meeting, we had the pleasure of learning more about just how effective physical activity is on brain health.
Many international researchers, including Jennifer Rabin, Jasmeer Chhatwal, Kirk Erickson, Katherine Bangen, Tianya Hous, Dorna Cadar, Priya Palta, Wanqing Wu, Richard Mayeux, Yian Gu, Katsuyuki Miura, and Marta Milà-Alomà, presented cohort studies that analyzed the magnitude of cognitive decline and dementia onset with physical activity. Collectively, the studies tracked over 13,000 cognitively normal participants ≥ 50 years of age with varying degrees of daily physical activity. The studies of Cadar and Palta reported that physical activity was associated with less cognitive decline and over a 40% decrease in the risk of developing dementia for up to 14 years after baseline assessments [5]. This risk could decrease as much as 60% in participants who had active lifestyles that started when they were young and even 50% in those that developed active lifestyles after the age of 50 [3]. Importantly all the studies demonstrated that in older populations, physical activity parallels a reduced risk of cognitive decline and dementia, highlighting the importance of exercise on brain health.
You may be wondering exactly how exercise can improve brain health. Recent studies have shown exercise can reduce brain amyloid-beta (Aβ) burden, hypometabolism, and atrophy (shrinkage). Put simply, exercise reduces protein and plaque build-up in the brain while protecting against brain shrinkage. In addition to decreasing harmful blockage to the brain, which causes atrophy, exercise may also stimulate the production of chemicals that further protect the brain [6,7]. Up until this point, however, few studies have analyzed how physical activity affects the relationships between Aβ deposition, brain volume and cognitive decline, all of which are signs of dementia and Alzheimer’s disease.
In what is known as the Harvard Aging Brain Study, 182 cognitively normal patients with an average age of 73 years, were asked to wear a pedometer for one week during waking hours to monitor their daily physical activity in terms of the number of steps they took [3]. Upon introduction to the study, the participants’ baseline brain physiology was measured with Aβ-PET (positron emission tomography) and MRI (magnetic resonance imaging) scans. Their cognitive abilities and vascular health were also assessed. Although there was no direct link between baseline Aβ levels and cognitive decline, individuals with a greater Aβ burden at baseline were more susceptible to cognitive decline over the 6-year follow-up. Among individuals with the highest detectable amount of Aβ in the brain, walking more than 8,300 steps a day prevented cognitive decline. Conversely, walking less than 2,900 steps a day accelerated cognitive decline in this subpopulation. Everyone’s brain volume lessened with age and Aβ burden at baseline correlated with a much steeper decline in brain health. The findings of this study were mirrored in another study that found less brain atrophy and cognitive decline in association with individuals with good vascular health. Collectively, these findings suggest that better physical fitness and cardiovascular health is protective against Aβ-mediated cognitive decline [3].
These results are particularly important as recent studies suggest that fewer than 20% of people over age 65 implement enough physical activity in their daily lives and dementia makes them even less likely to do so [8,9]. Because of this, personalized prevention and treatment methods for Alzheimer’s and dementia appear to be more promising. Physical activity can easily be tailored to fit within individuals’ limits and yield beneficial results. No, this doesn’t mean you need to seek help from personal trainers, or even join a gym to prevent dementia. “Physical activity” might seem daunting to some, but it need not be frightening. Physical activity is not as strict as exercise. Physical activity is movement in its simplest form; while exercise requires structure, repetition, and intention [10]. Incorporating activities that improve cardiovascular endurance and muscular strength are both beneficial in supporting brain health and cognition [11–13]. Thirty to sixty minutes of aerobic exercise (i.e. walking, hiking, biking) three or more days per week increases cerebral blood flow, as well as immediate and delayed memory abilities [11]. Resistance training (i.e. pilates, weight machines, free weights, bodyweight workouts) has been shown to increase growth factors and homocysteine supply to the brain. Building muscle and thereby reducing sarcopenia also allows for adults to continue to exercise later in life with lower risk of physical injury [12].
Planned, regular exercise can be important for establishing fitness and health goals, though it is not absolutely necessary for better brain health. After all, simply walking alone provides protection from cognitive decline and dementia [3]. What’s important is getting your blood pumping and muscles moving- it doesn’t matter how you choose to do so. The steps toward better brain health aren’t quite as difficult as they are cut out to be!
References
[1] Hörder, H., Johansson, L., Guo, X., Grimby, G., Kern, S., Östling, S., & Skoog, I. (2018). Midlife cardiovascular fitness and dementia. Neurology, 90(15). doi:10.1212/wnl.0000000000005290
[2] Buchman AS, Yu L, Wilson RS, et al. Physical activity, common brain pathologies, and cognition in community-dwelling older adults. Neurology. 2019;92(8):e811-e822. doi:10.1212/WNL.0000000000006954
[3] Rabin, J. S., et al. (2019). Associations of Physical Activity and β-Amyloid With Longitudinal Cognition and Neurodegeneration in Clinically Normal Older Adults. JAMA Neurology, 76(10), 1203. doi:10.1001/jamaneurol.2019.1879
[4] Kirk-Sanchez, N., & Mcgough, E. (2013). Physical exercise and cognitive performance in the elderly: Current perspectives. Clinical Interventions in Aging, 51. doi:10.2147/cia.s39506
[5] Palta P, et al. Leisure-time physical activity sustained since midlife and preservation of cognitive function: The Atherosclerosis Risk in Communities Study. Alzheimers Dement. 2019;15(2):273-281. doi:10.1016/j.jalz.2018.08.008
[6] Michelle Ploughman (2008) Exercise is brain food: The effects of physical activity on cognitive function, Developmental Neurorehabilitation, 11:3, 236-240, DOI: 10.1080/17518420801997007
[7] Cotman, C. W., et al. (2007). Exercise builds brain health: Key roles of growth factor cascades and inflammation. Trends in Neurosciences, 30(9), 464-472. doi:10.1016/j.tins.2007.06.011
[8] Dotinga, R. (2016, September 15). 31 Million Older Americans Aren’t Getting Enough Exercise.
[9] Physical Exercise and Dementia. (2015). Dementia Australia.
[10] Gummelt, D. (2015). Physical Activity vs. Exercise: What’s the Difference?
[11] Chapman, S. B., et al. (2013). Shorter term aerobic exercise improves brain, cognition, and cardiovascular fitness in aging. Frontiers in Aging Neuroscience, 5. doi:10.3389/fnagi.2013.00075
[12] Liu-Ambrose, T., et al. (2008). Exercise and cognition in older adults: Is there a role for resistance training programmes? British Journal of Sports Medicine, 43(1), 25-27. doi:10.1136/bjsm.2008.055616
[13] García-Soto E, López de Munaín ML, Santibáñez M. [Effects of combined aerobic and resistance training on cognition following stroke: a systematic review]. Revista de Neurologia. 2013 Dec;57(12):535-541.