Exercise helps improve cognition in healthy individuals as well as those with cognitive deficits
During the aging process, a variety of changes occur within the brain. These changes, which include decreases in neurogenesis or new neuron growth, detriments in the vasculature surrounding the brain tissue, and deterioration in the glia or support cells of the brain, cause a variety of functional changes for the aging individual. Cognitive decline is a frequent occurrence as we age, with some individuals progressing to Mild Cognitive Impairment (MCI) or dementia disorders, such as Alzheimer’s disease (AD). In fact, more than 16 million people in the United States are living with cognitive impairment, with 5.1 million of these individuals diagnosed with AD. Cognitive decline, however, is not an inevitable result of aging. Fortunately, a healthy lifestyle is one way to ward off age-related memory issues. Recent scientific evidence indicates that exercising throughout life helps to prevent cognitive decline and may even help ameliorate symptoms in patients with dementia.
A collection of work shows that in elderly individuals, higher levels of fitness predict higher levels of cognitive functioning (Prakash et al., 2015). Additionally, research that has examined the progression of cognition over the course of aging shows that higher levels of physical fitness delay or prevent age-related cognitive decline. A meta-analysis of this work that examined 15 studies, including 33,816 non-demented subjects followed over 1-12 years, determined that healthy individuals who report high levels of physical activity show a 38% reduction in the risk of cognitive decline (Sofi et al., 2011). Though these types of studies are informative, they are hampered by the fact that they often rely on self-reported physical activity measures or examine simple correlations of physical fitness and cognition. In order to answer the question of whether exercise enhances cognitive function, interventional studies are needed.
One recent interventional study examined the effect of various types of exercise on a variety of cognitive abilities in healthy elderly individuals (Iuliano et al., 2015). Eighty previously sedentary participants, aged 55 years and older (66.96±11.73 years), were randomly assigned to one of three exercise groups that trained for 12 weeks or a control group that performed no exercise. The three types of exercise groups included: a resistance group that performed high-intensity strength training of six muscles groups including the shoulders, arms, chest, abdomen, back and legs; a cardiovascular group that performed high-intensity cardiovascular training on either the treadmill, stationary bicycle, or step machine; and a postural group that performed low-intensity training using postural and balance exercises. Before and after the 12-week training period, participants underwent a series of neuropsychological tasks that assess cognitive functions that are known to deteriorate with age. This battery of tasks, which included the Attentive Matrices Test, the Raven’s Progressive Matrices Test, the Stroop Color Word Interference test, the Trail Making Test, and the Drawing Copy Test, assessed attention, abstract reasoning, inhibitory control, processing speed and mental flexibility, and motor planning respectively. They found that different types of training are beneficial to different aspects of cognitive function. Resistance training enhanced motor planning whereas cardiovascular training enhanced attention and abstract reasoning. Low-intensity postural training did not enhance any of the cognitive abilities examined.
Other work has examined the effects of long-term exercise in patients with MCI, which is a syndrome characterized by problems in memory and thinking. Approximately 10-20% of the United States population aged 65 years and older has been diagnosed with MCI, and these individuals have a higher likelihood of progressing to AD and other dementias. Suzuki et al. (2013) conducted a longitudinal study to see whether a six-month long multi-component exercise regimen could improve cognition in MCI patients. 100 elderly individuals, 65 years and older (75.4±7.1 years), living with MCI were randomly assigned to either an exercise group or an educational control group. The exercise group participated in a 90-minute exercise program, twice per week, that included aerobic exercise, strength training, balance training, and dual-task training where participants were asked to perform cognitive tasks (like creating a poem) while exercising. The control group attended two health-related education classes during the course of the 6 months. To assess cognitive function, before and after the 6-month period, all participants were required to complete the Mini-Mental State Examination (MMSE) and the cognitive subscale of the Alzheimer’s Disease Assessment Scale as well as remember a short story. Initially, the analyses revealed no significant differences between the two groups in the change in cognition over time. However, when the analyses were restricted to subjects who had amnestic MCI, a subtype of MCI characterized specifically by memory loss rather than impairments in thinking, planning, organization or judgement, the researchers found that compared to the control group who showed detriments in in cognitive functioning over the 6 months, exercisers significantly improved in general cognitive ability as assessed by the MMSE and short-term memory as assessed by story recall.
This collection of work shows that the types of cognitive processes most sensitive to physical activity depend on two brain regions involved in learning and memory, the prefrontal cortex and the hippocampus. The prefrontal cortex supports executive functioning, which includes attention, short-term or working memory, processing speed, decision-making, and the ability to switch between tasks or cognitive flexibility. The hippocampus, on the other hand, is involved in long-term memory, the ability to distinguish between stimuli or pattern separation, and spatial navigation or the ability to know where we are in space and navigate through our environment. The brain, however, is composed of a myriad of regions that support many different types of learning and memory, and a distinct possibility exists that exercise improves other aspects of cognition besides those that depend on the prefrontal cortex and hippocampus. Work in rodents certainly shows exercise-induced brain changes in areas such as the motor cortex, cerebellum, striatum, and amygdala, to name a few. Therefore, many questions remain to be answered regarding the effects of exercise on aspects of learning and memory dependent on other brain structures besides the prefrontal cortex and hippocampus.
In conclusion, exercise helps to decrease the risk for cognitive decline as well as help to slow the progression of memory loss in patients with MCI. Practically, this work suggests that we can maximize the cognitive benefits we receive from exercising at high- rather than low-intensities and by combining strength training with cardiovascular training. Additionally, exercise appears to be helpful in promoting cognitive function whether you are healthy or already suffer from cognitive decline. So go get exercising - it will help you function better physically as well as mentally!
References:
Iuliano, E., di Cagno, A., Aquino, G., Fiorilli, G., Mignogna, P., Calcagno, G., & Di Costanzo, A. (2015). Effects of different types of physical activity on the cognitive functions and attention in older people: A randomized controlled study. Experimental gerontology, 70, 105-110.
Prakash, R. S., Voss, M. W., Erickson, K. I., & Kramer, A. F. (2015). Physical activity and cognitive vitality. Annual review of psychology, 66, 769-797.
Sofi, F., Valecchi, D., Bacci, D., Abbate, R., Gensini, G. F., Casini, A., & Macchi, C. (2011). Physical activity and risk of cognitive decline: a meta‐analysis of prospective studies. Journal of internal medicine, 269(1), 107-117.
Suzuki, T., Shimada, H., Makizako, H., Doi, T., Yoshida, D., Ito, K., ... & Kato, T. (2013). A randomized controlled trial of multicomponent exercise in older adults with mild cognitive impairment. PloS one, 8(4), e61483.
