Physical fitness linked to lower cognitive impairment in dementia

Dr Eddy Davelaar from the Department of Psychological Sciences discusses the importance of physical fitness in offsetting cognitive impairment in adults with dementia.

 

Dementia and cognitive impairment cost the UK economy approximately £26 billion per year. The number of people with dementia in England and Wales has been projected to increase by 57% from 2016 to 2040, primarily because of extended life expectancy. Finding ways to slow its severity and progression could have life-changing effects for the 800,000 people estimated to be living with dementia in the UK.

With the increased incidence in dementia, people are interested to know whether it could be prevented through changes in their lifestyle, such as eating habits, exercise, and decreased environmental stress. Research does suggest that a healthy lifestyle lowers the risk of dementia. We were interested in physical fitness as one of the lifestyle factors. In our recent article published in Frontiers in Public Health, we asked the question of whether self-reported physical fitness is associated with cognitive, or thinking ability in people with dementia.

To assess this, we used a cross-sectional design with two groups. The first group was made up of 30 older individuals (aged 65+ years) with dementia, who were attending the Alzheimer’s café social events. Those people in the dementia group have lower cognitive performance than the 40 age-matched participants from our control group, who do not have dementia.

We tested everyone on a wide range of cognitive tests, such as verbal fluency, prospective memory, and clock drawing. We also administered a 15-item questionnaire on physical fitness, which asked about strength (eg. ability to lift things), balance, and aerobic conditioning (eg. taking a brisk walk or taking the stairs instead of lifts). Many studies have shown strong correlations between self-report and objective measures of physical fitness. In addition, this questionnaire is available to everyone for self-assessment.

Our findings showed that in the group of dementia patients, those with greater physical fitness also had a greater general cognitive ability. Even those patients with the best cognitive performance still performed worse than the healthy individuals, who did not show this link between physical and cognitive fitness. Thus, physical fitness seems to buffer dementia-related cognitive deterioration.

We ran a number of checks on the results and found that the association did not change when we controlled for the age of the participants, the number of years since dementia diagnosis, the type of dementia, or even whether the person used to be physically active when they were younger. The latter finding suggests that the current state of being physically fit and capable is key to observing this cognitive benefit.

There are at least two explanations for these findings. First, the cardiovascular hypothesis states that physical activity stimulates blood circulation in frontal-striatal circuits (neural pathways that connect frontal lobe regions with the basal ganglia that mediate motor, cognitive, and behavioural functions within the brain), that are critical in executive functioning, such as planning and reasoning.

A second hypothesis suggests that physical fitness measures, such as strength and balance, require efficient brain representations of motor plans. The processes by which these motor representations become more efficient also leads to enhanced cognitive representations. Both hypotheses underscore the expression, ‘what is good for the heart is good for the brain’.

We are currently in the process of addressing the question of whether physical fitness (using both self-report and objective measures) is associated with cognitive decline or cognitive impairment in the absence of dementia. This would assess whether greater physical fitness is associated with greater mental fitness in general, or with cognitive fitness specific in the context of dementia.

Future research could also extend this work using longitudinal study designs in order to address the question of whether a change in physical fitness is associated with a change in the risk of dementia, which has important implications for health policy and age-appropriate physical intervention programmes for both healthy individuals and dementia patients.

Read the original, peer-reviewed article: Increased Physical Fitness Is Associated with Higher Executive Functioning in People with Dementia (2017).

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