The Benefits of Physical Activity on Preserving Cognitive Function in the Aging Brain

We all know someone in our immediate surroundings who suffers from cognitive impairment. Cognitive impairment can be an early warning sign of dementia.

Preserving cognitive function is a major challenge in a rapidly aging population. The World Health Organization predicts that by 2050, 1.5 billion people will be 65 years or older. This figure shows that maintaining cognitive abilities in old age has become a public health priority.

It is therefore essential to identify behaviors that can slow cognitive decline and even improve cognitive performance over time. This will reduce the emotional burden on patients and their families and preserve the quality of life of the aging population.

Physical activity has been described as the "best buy in medicine" (Loprinzi, 2015). An active lifestyle not only reduces the risk of chronic diseases, but also preserves cognitive skills, particularly "executive function" (EF). The concept of EF consists of three distinct but complementary components, namely: mental flexibility, working memory, and inhibitory control of unhealthy behaviors (Miyake & Friedman, 2012).

Exercise has positive effects on cognitive function, particularly executive function

There is a bidirectional and reciprocal relationship between physical activity and EF. An analysis of data collected from 4555 older adults over 6 years in the English Longitudinal Study of Ageing (ELSA) found that physical activity and EF were closely related. Sustained physical activity contributed to high EF performance, and conversely, higher levels of EF translated into greater physical activity (Daly et al., 2015). In contrast, individuals with poor EF experienced a decline in physical activity levels.

Relative to other aspects of cognitive function, exercise had the greatest beneficial effect on executive function (Colcombe & Kramer, 2003).

From exercise to improved cognitive function: the role of neuroplasticity

A growing body of research in both animals and humans highlights the role of neuroplasticity as a key neurobiological mechanism for improving cognitive function, particularly EF performance, following increased physical activity.

Neuroplasticity, also known as neural plasticity or brain plasticity, is a lifelong process that modifies existing neural networks through growth (neurogenesis) and reorganization in response to changes in environment or behavior. These changes range from the establishment of new connections through individual neural pathways to systematic adjustments involving cortical remodeling.

The mechanisms underlying exercise-induced neuroplasticity involve several neurotrophic growth factors, such as brain-derived neurotrophic factor (BDNF), whose expression is upregulated by exercise. In addition, neuroplasticity is also enhanced by exercise-modulated angiogenesis and microglial activation (the major immune cells of the CNS), as well as the maintenance of a healthy cerebral microenvironment.

Besides these suggested mechanisms, physical activity also exerts a beneficial effect on inflammatory markers, which may represent an additional explanation for how exercise improves EF.

Physical activity is part of a broader set of health behaviors capable of producing marked changes in executive function, such as:

• A healthy diet: positively influences cognitive health by providing high levels of antioxidants and anti-inflammatory agents that mitigate oxidative stress in the brain and thus neurodegeneration, while simultaneously promoting neurogenesis and boosting neurotrophic factors.
• In contrast, smoking, drug, and alcohol use have negative effects on cognitive function, particularly EF. Ranzi et al (2004), reported that heavy smokers showed poorer performance on EF tests than moderate smokers and light/never smokers, suggesting a possible dose-response relationship between smoking and EF. Similarly, Sabia et al. (2012) found that recent ex-smokers suffered greater cognitive decline than long-time ex-smokers, suggesting that the detrimental effect of smoking may be reversible. Beyond the acute harmful effects of alcohol on EF, chronic alcohol use leads to a decline in EF, which persists despite detoxification. Alcohol-related cognitive decline has been attributed to neural damage and decreased neurogenesis.

Executive function is a key driver for healthy behavior

People with higher levels of EF are more likely to follow through on their good intentions because they are better able to resist temptation and eliminate bad habits that result in physiological dysfunction and poor health.

A mutually reinforcing relationship between positive health behaviors and EF lays the foundation for an integrated therapeutic approach.

Regardless of whether an intervention starts with a positive health behavior or a more effective cognitive skill, both physical and cognitive benefits result over time. Consider an initiative aimed at increasing physical activity by fitting participants with a pedometer. With increased awareness of progress toward their goals and motivation to monitor their activity, participants provided with a pedometer spontaneously increased their daily exercise routine.

Conclusions and future directions

There is growing evidence that a healthy lifestyle, especially physical activity, can reduce the rate of cognitive decline observed in aging and help delay the onset of EF impairment by improving mental flexibility, working memory and inhibitory control.

Neurobiological mechanisms have been shown to be responsible for the protective effects on cognition, particularly EF, achieved by exercise and a healthy diet, while avoiding excessive exposure to neurotoxins (e.g., alcohol and tobacco).

The bidirectional relationship between positive health behaviors and EF warrants proactive and early engagement in healthy living to initiate their critical interaction, thereby mitigating age-related cognitive decline.

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