Dementia is a defined as a cognitive decline resulting in a decline in daily function. The most common cause of dementia is Alzheimer’s Dementia (AD). In the United States there are over 5.3 million people in the United States who have AD. This number is estimated to triple by 2050. The main risk factor for developing AD is aging. The majority of other major risk factors including diabetes, obesity, and physical inactivity, are potentially modifiable thus we have control over. (Barnes, 2011)
Out of all the risk factors physical inactivity may have the largest impact on prevention of AD. It has been estimated that over 1.1 million cases of AD are potentially attributable to physical inactivity.(Barnes, 2011) Such that those who engage in the highest physical activity have been estimated to have a decreased risk of AD by 45% compared to lowest physical activity category. (Hamer, 2009)
Exercise has indirect effects of improving your brain by improving health conditions that are also risk factors for AD. Specifically exercise results in weight loss that then decreases risk of obesity. Diabetes and hypertension are also improved with exercise. Improvement in these health conditions, then, potentially may result in a decrease risk of strokes.
Epidemiological studies have shown that increased lifetime engagement in physical activity can reduce the risk of developing dementia in cognitively normal elderly persons. (Taafee, 2007) Specially, moderate activity during mid-life is associated with 39% decreased risk of developing mild cognitive impairment (which is one of first stage of AD). The good new is that even starting an exercise program later in life is also associated with a 32% lower risk for mild cognitive impairment. (Bherer, 2013).
Evidence is also growing that exercise may not only reduce the risk of dementia but also have some benefit in improving memory as we age and if you already have dementia. Exercise has been shown to preserves memory, processing speed, and executive function that typically decline with age. (Bherer, 2013) Exercise in patients with dementia overall has a positive effect on cognitive function based on a meta- analysis of 18 randomized studies. (Groot, 2016) Exercise also improves balance, mobility and thus reduced the risk of falls.
The beneficial effects of exercise are supportive by the brain imaging research that has been done. These studies have noted a decrease rate of the shrinking of brain in those who have higher aerobic fitness levels. Also shown is that the area involved in memory, the hippocampus, has a larger volume with exercise. (Kelly, 2014)
How exercise is believed to result in these changes are of course not completely know. Things that are believed is that exercise has neuro-protective effects on the brain. One of the main factors believed to be contributive to age related diseases and AD is oxidative stress mediated by reactive oxygen species. Exercise has been shown to decreases reactive oxygen species and increases the activity of antioxidant systems. Exercise also increases a neuropeptide, brain derived neurotropic factor (BDNF) that helps to promote neurogenesis in the hippocampus. (Radak, 2010) (Bherer, 2013)
How much exercise is needed? To reduce risk of cognitive decline in cognitively normal persons over the age of 65 the World Health Organization recommends: A weekly minimum of 150 minutes of moderate intensity aerobic activity or 75 minutes of vigorous intensity aerobic activity. (Groot, 2016) I would also recommend adding some muscle strengthening exercises to help improve strength. To help prevent falls consider adding in some yoga or Tai Chi to help with balance.
Barnes, D. Y. (2011). The projected effect of risk factor reduction on Alzheimer’s disease prevalence. Lancet Neurology, 10, 819-828.
Bherer, L. E. (2013). A Review of the Effects of Physical Activity and Exercise on Cognitive and Brain Functions in Older Adults. Journal of Aging Research, 1-8.
Erickson, E. E. (2011). Exercise training increases size of hippocampus and improves memory. Proceeding of the National Academy of Sciences of the United States of America , 108 (7), 3017-3022.
Groot, C. E. (2016). The effect of physical activity of cognitive function in patients with dementia: A meta-analysis of randomized control trials. Ageing Research Reviews , 25, 13-23.
Hamer, M. C. (2009). Physical activity and risk of neurodegenerative disease: a systemic review of prospective evidence. Psychol. Med , 39, 3-11.
Kelly, M. E. (2014). The impact of exercise on the cognitive functioning of healthy older adults: A systemic review and meta-analysis. Aging Research Reviews , 16, 12-31.
Radak, Z. E. (2010). Exercise Plays a Preventive Role Against Alzhemier’s Diease. Journal of Alzheimer’s Diease , 20, 777-783.
Soli, F. (2011). Physical activity and risk of cognitive decline: a meta- analysis of prospective studies. Journal of Internal Medicine, 269, 107-117.
Taafee, D. e. (2007). Physical activity, physical function, and incident dementia in elderly men: the Honolulu-Asia Aging Study. Journal Gerontology , 63 (5), 529-535.