Physical activity’s impact on brain function

As scientists accumulate more and more data about how the brain works, researchers report regular physical activity can protect against dementia, particularly Alzheimer’s disease. It is never too late to reap physical activity’s benefits, if your body allows it.

Dementia is the overarching term to identify symptoms characterized by difficulties with such thinking skills as memory, language, problem-solving, and more.

Alzheimer’s disease represents just one dementia sub-category regarding the degeneration of brain nerve cells as well as the accumulation of the abnormal proteins beta-amyloid and phosphorylated tau in the brain.

Alzheimer’s brain changes represent the most common contributor to dementia, accounting for 60-80 percent of all dementia cases. Large autopsy studies recently show more than half of individuals with Alzheimer’s dementia present specific brain changes (pathology) associated with other causes of dementia, including:

• Cerebrovascular disease, in which brain blood vessels are damaged and/or brain tissue is injured due to lack of blood, oxygen, or nutrients
• Lewy body disease, in which abnormal aggregations or clumps of the protein alpha-synuclein (in neurons of the brains’ cortex) produce dementia. Actor/comedian Robin Williams was diagnosed with the disease.

Rising rates of dementia and Alzheimer’s

More than 6.5 Americans million aged 65 and older are living with Alzheimer’s, and 74 percent are age 75 or older. (Stock image.)

The increasing prevalence of dementia and Alzheimer’s disease in our population portends a disturbing public health emergency.

• More than 6.5 million Americans aged 65 and older are living with Alzheimer’s disease, and 74 percent are age 75 or older.
• Women represent about two-thirds of Americans with Alzheimer’s disease.
• Older Black Americans are about twice as likely to have Alzheimer’s disease or other forms of dementia.
• Older Hispanics are about 1.5 times as likely to have Alzheimer’s disease or other forms of dementia.
• 1 in 3 seniors dies with Alzheimer’s or other forms of dementia. It kills more than breast cancer and prostate cancer combined.
• Deaths from Alzheimer’s disease more than doubled between 2000-19, while those from heart disease — the leading cause of death — have decreased.
• At age 70, seniors living with Alzheimer’s disease are twice as likely to die before age 80 than those without Alzheimer’s.
• By 2050, 12.7 million people aged 65 and older will develop Alzheimer’s disease.

What to watch for

The major symptoms of Alzheimer’s disease include difficulty remembering recent conversations, names, or events. Apathy and depression are early symptoms, as well. Later symptoms include impaired communication, disorientation, confusion, poor judgment, behavioral changes, and, ultimately, difficulty speaking, swallowing, and walking.

Exercise and brain plasticity

Recent research evidence targeting possible behavioral interventions shows that physical activity can improve brain function and delay or prevent the onset of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease, too.

While the underlying mechanisms remain unclear, recent studies suggest physical activity-induced activation of peripheral systems such as muscle, gut, liver, and adipose tissue may affect neural plasticity. Specifically, current thinking suggests the myokines (molecular mediators originating from contracting muscle fibers) called Cathepsin B (CTSB) and the brain-derived neurotrophic factor (BDNF) possess robust neuroprotective effects that enhance brain function.

Current research focuses on how and why exercise increases the amount of CTSB and BDNF circulating in the blood, and thereby increases brain plasticity.

Links between action and cognition

Physical activity during mid-life
Two research methodologies are considered robust and trustworthy sources of evidence. Prospective research follows a group of people over time, and meta-analyses research systematically synthesizes findings from multiple studies.

Several prospective and meta-analytic studies have examined middle-aged individuals and the effects of physical activity on their thinking and memory in later life. The consensus shows regular physical activity can significantly reduce the risk of developing dementia by about 30 percent. For Alzheimer’s disease, specifically, the risk can be reduced by 45 percent!

One study looked at the health behaviors of more than 2,000 men in Wales and followed them for 35 years. Scientists assessed the impact of the following:

• Regular physical activity
• Not smoking
• Moderate alcohol intake
• Healthy body weight
• Healthy diet

They found physical activity had the greatest effect on reducing the risk of dementia. Overall, people who exhibited four or five of the listed behaviors were up to 60 percent less likely to develop dementia.

In the short term, aerobic physical activity also can improve cognitive performance of healthy adults on “thinking” tests. The results of 29 clinical trials suggest that a month or more of regular aerobic physical activity can result in improvements in memory, attention, and processing speed when compared with regular nonaerobic physical activity such as stretching and toning.

Physical activity during later life

One of U-M’s great traditions is welcoming back elder alumni members of the Michigan Marching Band for Alumni Weekend. (Image credit: Michigan Photography.)

Although less research has been done with healthy older people, some evidence exists that shows older people also can reduce dementia risk with regular physical activity. In a study of 716 people at an average age of 82 years, people in the bottom 10 percent in terms of daily physical activity were more than twice as likely to develop Alzheimer’s disease as those in the top 10 percent.

A meta-analysis involving 27 studies examined the effect of physical activity on brain function in people aged 60 and older. In 26 of the studies, a clear link existed between increased physical activity levels and cognitive performance, suggesting physical activity might be an effective way to reduce cognitive decline during later life.

Aerobic physical activity also has been shown to affect healthy older people’s brains. In one study, a year of aerobic exercise resulted in a small increase in the size of the hippocampus (the key brain area involved in memory), which was the equivalent of reversing one to two years of age-related brain shrinkage.

Start moving if you can!

Just remember: Regular physical activity can significantly reduce the risk of developing dementia or Alzheimer’s disease. Set a timer to remind yourself to get up and dance, walk, or jog. Even walking briskly for 20-30 minutes per day can:

• Promote cerebral (brain) blood flow and brain metabolic functions
• Enhance muscle and nerve biogenesis (the synthesis of substances)
• Support neurogenesis (the process by which new neurons are formed in the brain)
• Reduce oxidative stress and cell senescence (deterioration with age)
• Reduce neuroinflammation (activation of the brain’s innate immune system in response to an inflammatory challenge)

Movement is one way we can reduce our risk of these diseases at any life stage. Of course, it’s always a good idea to mix and match. Combine physical, social, and mental activities to get the most benefit for your brain.

References:

• Alzheimer’s Association. 2021 “Alzheimer’s disease facts and figures.” Alzheimer’s & Dementia. 2021;17:327.
• Blumen, H.M., et al. “Randomized controlled trial of social ballroom dancing and treadmill walking: Preliminary findings on executive function and neuroplasticity from dementia-at-risk older adults.” The Journal of Aging and Physical Activity. 2022 Dec 14:1.
• Brenowitz, W.D., et al. “Mixed neuropathologies and estimated rates of clinical progression in a large autopsy sample.” Alzheimer’s & Dementia. 2016;13:654.
• GBD 2019 “Dementia forecasting collaborators estimation of the global prevalence of dementia in 2019 and forecasted prevalence in 2050: an analysis for the global burden of disease study 2019.” Lancet Public Health. 2022;7:e105–e125
• Hays Weeks, C.C., et al. “The independent walking for brain health intervention for older adults: Protocol for a pilot randomized controlled trial.” JMIR Research Protocols. 2022 Dec 19. doi: 10.2196/42980. Epub ahead of print. PMID: 36535765.
• Jia, R.-X., et al. “Effects of physical activity and exercise on the cognitive function of patients with Alzheimer’s disease: A meta-analysis.” BMC Geriatrics. 2019;19:181.
• Park, C., Mishra, et al. “Tele-medicine based and self-administered interactive exercise program (tele-exergame) to improve cognition in older adults with mild cognitive impairment or dementia: A feasibility, acceptability, and proof-of-concept study.” International Journal of Environmental Research and Public Health. 2022;19(23):16361.
• Qiu, C., et al. “Epidemiology of Alzheimer’s disease: Occurrence, determinants, and strategies toward intervention.” Dialogues in Clinical Neuroscience. 2009;11:111.
• Sakatani, K., et al. “Effects of exercise-diet therapy on cognitive function in healthy elderly people evaluated by deep learning based on basic blood test data.” Advances in Experimental Medicine and Biology. 2022;1395:139.
• Yang, H.D., et. al. “History of Alzheimer’s Disease.” 2016. Dementia and Neurocognitive Disorders. 15(4):115.
• Zhang, S., et al. “The effect of aerobic exercise on cognitive function in people with Alzheimer’s disease: A systematic review and meta-analysis of randomized controlled trials.” International Journal of Environmental Research and Public Health. 2022;19(23):15700.
• Zhou, S., et al. “Physical activity improves cognition and activities of daily living in adults with Alzheimer’s disease: A systematic review and meta-analysis of randomized controlled trials.” 2022. International Journal of Environmental Research and Public Health. 19(3):1216.

(Lead image: iStock photo.)