Exercise and Cognitive Function: Increased Fitness Improves Cognition in Older Adults and Those with Chronic Medical Conditions

INTRODUCTION

Cognitive impairment is prevalent and associated with high personal and societal costs. An estimated 13 to 16 million Americans are believed to experience some level of cognitive dysfunction (1), and this dysfunction is associated with poorer quality of life (2), greater risk for disability (3), and increased mortality risk (4). Unfortunately, despite the success of stimulant mediations (5) and cholinesterase inhibitors (6), many cognitively impaired persons obtain insufficient benefit from pharmacological intervention for their symptoms.

Researchers have sought to identity other interventions with the potential to improve cognitive outcomes in those suffering from chronic medical conditions. Physical fitness has been associated with improved cognitive functioning in persons across the lifespan, including children (7), young adults (8), middle-aged adults (9), and older adults (10). Regular exercise supports brain health and is associated with a decreased risk for age-related dementia and cognitive decline (11). Given these findings, exercise interventions may ultimately prove to be an essential component in improving or maintaining cognition throughout the lifespan.

The goal of this paper is to briefly review and integrate the current literature on the relationship between exercise/physical activity and cognitive function, with a particular focus on older adults and persons with chronic medical conditions, such as cardiovascular disease (CVD) and obesity. These areas of emphasis were chosen as they have important societal implications for public health. For example, by 2030, the number of adults over the age of 65 years is expected to rise to 72 million (12). In regards to chronic medical conditions, an estimated 85.6 million adults in the United States have some form of CVD (13). Similarly, more than two-thirds of American adults are now overweight or obese (14). Each of these is associated with greater risk for cognitive impairment and, as highlighted below, may be alleviated through exercise.

ACUTE VERSUS CHRONIC EXERCISE AND COGNITIVE FUNCTIONING

Numerous studies suggest that acute exercise may produce immediate cognitive benefits. Exercising for as little as 30 min results in improved executive functioning (15,16), memory (17), and attention (18). A recent review also concluded that submaximal exercise performed for 60 min can also produce benefits in information processing (19). Consistent with such findings, a meta-analysis also found exercise resulted in improved executive functioning during, immediately after, and following a brief delay, though only small effect sizes were achieved (20). However, despite these encouraging effects, high-intensity exercise can actually suppress cognitive function under certain circumstances, particularly with excessive fatigue or dehydration (21,22).

In addition to these acute effects, there is growing evidence that regular physical activity and/or participating in an exercise intervention can produce lasting cognitive benefits for many individuals. A randomized controlled trial employing a 12-month cycling intervention structured as 1 h a day, three times per week, stabilized cognitive functioning in a group of healthy older adults (23). Similarly, Lieberman and colleagues (24) found improved reaction time in females following 10 weeks of the U.S. Army Basic Combat Training course. Regular exercise has also been found to be protective against cognitive decline and dementia in older cohorts (10, 25,26).

FITNESS AND COGNITIVE FUNCTIONING

Exercise produces many positive physiological changes with the potential to promote better neurocognitive outcomes, including improved memory, enhanced executive functioning, and positively influence cerebrovascular structures (27). A complete review is beyond the scope of the current work, but studies demonstrating the benefits of physical activity on structural and functional brain outcomes will be highlighted below.

CLINICAL IMPLICATIONS

Cognitive functioning is important in everyday life and can be particularly important for those suffering from chronic conditions that need to adhere to complex medical regimens. For example, after undergoing bariatric surgery, individuals often need to adhere to a sophisticated and often changing pattern of diet, medication management, and monitoring of conditions like blood pressure (74). Cognitive functioning often plays a role in the success of aftercare requirements for bariatric surgery patients (102), and cognitive deficits are associated with reduced weight loss after these procedures (103). A similar relationship between cognitive dysfunction and reduced treatment adherence is found in persons with conditions like CVD (104, 105), type 2 diabetes mellitus (106), Parkinson's disease (107), and HIV (108). Interventions to preserve or even improve cognitive function in high-risk patients may lead to better clinical outcomes. In the obese population, exercise is related to decreased weight, as well as reduction in symptoms associated with comorbid conditions (e.g., hypertension, type 2 diabetes, mellitus, etc.) and improved cognitive ability.

SUMMARY AND FUTURE DIRECTIONS

The rapidly growing literature demonstrates that exercise is beneficial for cognitive functioning in older adults and persons with chronic medical conditions. Recent research shows exercise is associated with both acute and persistent improvements in multiple cognitive domains. These gains in cognitive functioning are paralleled by positive changes in important structural areas of the brain responsible for cognitive ability, such as the hippocampus and prefrontal cortex. The benefits of exercise on cognition can be seen in many populations but are often most pronounced in those at greatest risk for cognitive decline. For instance, exercise is beneficial and protective for older adults, often improving executive functioning, attention, and memory. Similar to older adults, exercise is also advantageous to those with chronic medical conditions. Patients with CVD (e.g., HF, CVA) demonstrate improvements in global cognitive functioning, executive functioning, attention, and memory.

Such findings encourage additional research to identify the most acceptable and effective types of exercise programs. Many older adults are sedentary, and this population identifies numerous obstacles to participation in land-based exercise, such as time constraints, lack of motivation/determination, lack of familiarity with recreation facilities, fear of falling, poor physical health, and lack of knowledge about recommended type and intensity of activity (109–113).

There is also much to be learned about the underlying mechanisms for the neurocognitive benefits of exercise. Studies employing advanced neuroimaging (e.g., fMRI, magnetic resonance spectroscopy, arterial spin labeling, and biomarkers associated with both physical activity and neurological outcomes [e.g., brain derived neurotrophic factor, insulin growth factor-1]) would facilitate greater understanding of the physiological underpinnings for the neurocognitive benefits of physical activity and exercise. Similarly, work is also needed to better understand the relative contribution of aerobic versus resistance training exercises. Past work suggests that both provide cognitive benefits (114) and that the combination is effective in persons with a range of neurological conditions (115); however, their differential physiological effects raise the possibility that they make a unique contribution to neurological outcomes.