Physical Activity and Dementia
Many recent studies have provided evidence that lack of physical activity is an important risk factor for cognitive decline in aging. Regular exercise seems to convey a protective effect on the brain even if initiated after midlife. Clinical trials in older adults failed to show consistent memory improvement after exercise intervention. These differences may be the result of variable length of follow up and or harmful effects from medications.
Many animal studies have confirmed that exercise enhances the brain’s ability to remodel and grow (neuroplasticity). How exercise improves neuroplasticity is still unclear. The leading theory is that aerobic exercise improves cerebral blood flow to the hippocampus (the part of the brain that stores episodic memory). This, in turn, may prevent or delay shrinkage of the brain. The improved brain perfusion may be due to the growth of new blood vessels in the brain (neurovascular angiogenesis).
In a randomized controlled trial of 120 older adults, exercise training increased hippocampal volume by 2%. This effectively reversed age-related volume loss by 1-2 years. There is also evidence that physical activity levels may change the course of the disease in preclinical Alzheimer’s. Animal models suggest that exercise improves degradation and clearance of beta-Amyloid, an abnormal protein found in the brain of patients with Alzheimer’s. Exercise also may influence modifiable risk factors for Alzheimer’s disease such as insulin-resistance, and hypertension that could lead to hardening of the arteries and stroke.
Although moderate exercise carries minimal health risk, it’s important to know that nervous tissue growth and repair (neurogenesis) declines with age. In addition, older adults mobility may be hampered by frailty. This can lead to harmful effects of exercise such as falls or cardiac arrhythmias. Before initiating any exercise regimen always consult your provider.
The current exercise recommendations from the Global Council of Brain Health are: 150 minutes of weekly, moderate-intense aerobic activity such as walking, running, or dancing in addition to leading a physically active life. Examples of an active lifestyle including walking to work or to the store instead of driving; taking the stairs instead of the elevator; parking further away from a destination and walking; or engaging in regular hobbies and sports such as yoga, dancing, or gardening.
 Tolppanen A-MM, Solomon A, Kulmala, et al., Leisure-time physical activity from mid- to late life, body mass index, and risk of dementia. Alzheimer’s Dement 2015; 11: 434-443000000.
 Duzel E, Van Praag H, Sendtner M, Can physical exercise in old age improve memory and hippocampal function? BRAIN 2016; 139:662-673.
 Erickson KI, Voss MW, Prakash RS, et al., Exercise training increases size of hippocampus and improves memory, Proc Natl Acad Sci USA 2011; 108: 3017-22.
 GCBH. The brain-body connection: GCBH recommendations on physical activity and brain health, Washington DC: Global council on brain health, 2016.