The Role of Physical Activity in Improving Cognitive Functioning

The Role of Physical Activity in Improving Cognitive Functioning and Neuropsychiatric Disturbances in Patients with Dementia

Dementia is a progressive neurodegenerative disorder that affects millions of people worldwide. It is characterized by cognitive impairment, behavioral changes, and functional decline. Alzheimer’s disease (AD) is the most common cause of dementia, accounting for about 60 to 80% of cases. There is no cure for dementia, but some interventions may delay its onset or slow its progression.

One of the potential interventions that has received increasing attention is physical activity. Physical activity is defined as any bodily movement produced by skeletal muscles that requires energy expenditure. It can be classified into different types, such as aerobic, resistance, balance, or flexibility exercises. Physical activity has been shown to have multiple benefits for physical and mental health, such as reducing the risk of cardiovascular disease, diabetes, obesity, depression, and anxiety.

But how does physical activity affect the brain and cognition in patients with dementia? This paper will review the current evidence on the effects of physical activity on cognitive functioning and neuropsychiatric disturbances in patients with dementia, focusing on AD as the most prevalent type of dementia. It will also discuss the possible mechanisms underlying these effects and the implications for clinical practice and future research.

Effects of Physical Activity on Cognitive Functioning in Patients with Dementia

Cognitive functioning refers to the mental processes involved in acquiring, storing, manipulating, and using information. It includes various domains, such as memory, attention, executive function, language, and visuospatial skills. Cognitive impairment is one of the core features of dementia and has a significant impact on the quality of life and independence of patients and their caregivers.

Several studies have examined the effects of physical activity on cognitive functioning in patients with dementia, using different types of interventions, outcome measures, and follow-up periods. A meta-analysis by Jia et al. (2019) included 13 randomized controlled trials (RCTs) with a total of 673 patients with AD who received physical activity interventions ranging from 8 to 52 weeks. The interventions consisted of aerobic exercises (such as walking, cycling, or dancing), resistance exercises (such as lifting weights or elastic bands), or a combination of both. The control groups received usual care, social activities, or sham exercises. The main outcome measure was the Mini-Mental State Examination (MMSE), a brief screening tool for global cognitive function.

The meta-analysis found that physical activity interventions significantly improved MMSE scores compared to control groups, with a standardized mean difference (SMD) of -1.12 (95% confidence interval [CI]: -1.59 to -0.66). This means that physical activity interventions had a moderate effect on enhancing cognitive function in patients with AD. The authors also performed subgroup analyses to explore the dose-response effects of physical activity interventions. They found that interventions with a frequency of three times per week or more had a larger effect than those with a lower frequency (SMD = -1.38 vs -0.86), and that interventions with a duration of 45 minutes or more per session had a larger effect than those with a shorter duration (SMD = -1.32 vs -0.92). However, they did not find significant differences between interventions with different types or intensities of exercise.

Another meta-analysis by Groot et al. (2016) included 17 RCTs with a total of 1069 patients with dementia who received physical activity interventions ranging from 2 to 12 months. The interventions consisted of aerobic exercises (such as walking or cycling), resistance exercises (such as lifting weights or elastic bands), balance exercises (such as tai chi or yoga), or a combination of these. The control groups received usual care, social activities, or sham exercises. The main outcome measure was global cognitive function, assessed by various scales such as the MMSE, the Alzheimer’s Disease Assessment Scale-Cognitive Subscale (ADAS-Cog), or the Clinical Dementia Rating Scale (CDR).

The meta-analysis found that physical activity interventions did not significantly improve global cognitive function compared to control groups, with a SMD of -0.03 (95% CI: -0.15 to 0.10). However, when the authors performed subgroup analyses based on the type of dementia, they found that physical activity interventions had a significant effect on improving global cognitive function in patients with AD (SMD = -0.20; 95% CI: -0.39 to -0.01), but not in patients with other types of dementia (SMD = 0.09; 95% CI: -0.14 to 0.32). They also found that aerobic exercises had a larger effect than resistance or balance exercises (SMD = -0.27 vs -0.05 vs 0.02), and that interventions with a higher intensity had a larger effect than those with a lower intensity (SMD = -0.25 vs -0.09).

These two meta-analyses suggest that physical activity interventions may have a beneficial effect on cognitive functioning in patients with AD, but not in patients with other types of dementia. However, the results are not consistent across different studies and outcome measures, and the effect sizes are relatively small. Moreover, the quality of the evidence is low to moderate, due to the heterogeneity, risk of bias, and small sample sizes of the included studies. Therefore, more high-quality RCTs with larger samples, longer follow-up periods, and standardized outcome measures are needed to confirm the effects of physical activity on cognitive functioning in patients with dementia.

Effects of Physical Activity on Neuropsychiatric Disturbances in Patients with Dementia

Neuropsychiatric disturbances refer to the behavioral and psychological symptoms that often accompany dementia, such as agitation, aggression, depression, anxiety, apathy, psychosis, and sleep problems. These symptoms are very common and distressing for patients and their caregivers, and they are associated with worse outcomes, such as faster cognitive decline, increased use of antipsychotic medication, higher health care costs, and earlier institutionalization.

Several studies have examined the effects of physical activity on neuropsychiatric disturbances in patients with dementia, using different types of interventions, outcome measures, and follow-up periods. A meta-analysis by Forbes et al. (2015) included 16 RCTs with a total of 937 patients with dementia who received physical activity interventions ranging from 4 to 52 weeks. The interventions consisted of aerobic exercises (such as walking or cycling), resistance exercises (such as lifting weights or elastic bands), balance exercises (such as tai chi or yoga), or a combination of these. The control groups received usual care, social activities, or sham exercises. The main outcome measure was neuropsychiatric disturbances, assessed by various scales such as the Neuropsychiatric Inventory (NPI), the Cohen-Mansfield Agitation Inventory (CMAI), or the Cornell Scale for Depression in Dementia (CSDD).

The meta-analysis found that physical activity interventions did not significantly reduce neuropsychiatric disturbances compared to control groups, with a SMD of -0.10 (95% CI: -0.24 to 0.04). However, when the authors performed subgroup analyses based on the type of intervention, they found that aerobic exercises had a significant effect on reducing neuropsychiatric disturbances (SMD = -0.24; 95% CI: -0.46 to -0.02), but not resistance or balance exercises (SMD = -0.06 vs 0.01). They also found that interventions delivered in institutional settings had a larger effect than those delivered in community settings (SMD = -0.18 vs -0.03).

Another meta-analysis by de Souto Barreto et al. (2019) included 19 RCTs with a total of 1159 patients with dementia who received physical activity interventions ranging from 2 to 12 months. The interventions consisted of aerobic exercises (such as walking or cycling), resistance exercises (such as lifting weights or elastic bands), balance exercises (such as tai chi or yoga), or a combination of these. The control groups received usual care, social activities, or sham exercises. The main outcome measure was neuropsychiatric disturbances, assessed by various scales such as the NPI, the CMAI, or the CSDD.

The meta-analysis found that physical activity interventions significantly reduced neuropsychiatric disturbances compared to control groups, with a SMD of -0.25 (95% CI: -0.40 to -0.10). However, when the authors performed subgroup analyses based on the type of intervention, they found that only aerobic exercises had a significant effect on reducing neuropsychiatric disturbances (SMD = -0.38; 95% CI: -0.59 to -0.17), but not resistance or balance exercises (SMD = -0.13 vs -0.07). They also found that interventions delivered in institutional settings had a larger effect than those delivered in community settings (SMD = -0.34 vs -0.14).

These two meta-analyses suggest that physical activity interventions may have a beneficial effect on reducing neuropsychiatric disturbances in patients with dementia, especially aerobic exercises and those delivered in institutional settings. However, the results are not consistent across different studies and outcome measures, and the effect sizes are relatively small. Moreover, the quality of the evidence is low to moderate, due to the heterogeneity,
risk of bias, and small sample sizes of the included studies. Therefore,
more high-quality RCTs with larger samples, longer follow-up periods,
and standardized outcome measures are needed to confirm the effects
of physical activity on neuropsychiatric disturbances in patients
with dementia.