Someone dies somewhere in the world every 10 seconds owing to physical inactivity – 3.2 million people a year according to the World Health Organisation (WHO).
From the age of 50, there is a gradual decline not just in physical activity but also in cognitive abilities since the two are correlated.
But which of them influences the other?
Does physical activity impact on the brain or is it the other way around?
To answer this question, researchers from the University of Geneva (UNIGE), Switzerland, and the NCCR Lives Swiss National Centre of Competence in Research used a database of over 100,000 people aged 50-90 whose physical and cognitive abilities were measured every two years for 12 years.
The findings, which are published in the journal Health Psychology, show that – contrary to what was previously thought – cognitive abilities ward off inactivity much more than physical activity prevents the decline in cognitive abilities. All of which means we need to prioritise exercising our brains.
The literature in this area has been looking at the impact of physical activity on cognitive skills for a number of years.
“Correlations have been established between these two factors, particularly in terms of memory, but also regarding the growth and survival of new neurons,” begins Boris Cheval, a researcher at UNIGE’s Swiss Centre for Affective Sciences (CISA).
“But we have never yet formally tested which comes first: does physical activity prevent a decline in cognitive skills or vice versa? That’s what we wanted to verify.”
What came first: the chicken or the egg?
Earlier studies based on the correlation between physical activity and cognitive skills postulated that the former prevent the decline of the latter. “But what if this research only told half the story?
That’s what recent studies suggest, since they demonstrate that our brain is involved when it comes to engaging in physical activity,” continues the Geneva-based researcher.
The UNIGE researchers tested the two possible options formally using data from the SHARE survey (Survey of Health, Aging and Retirement in Europe), a European-wide socio-economic database covering over 25 countries.
“The cognitive abilities and level of physical activity of 105,206 adults aged 50 to 90 were tested every two years over a 12-year period,” explains Matthieu Boisgontier, a researcher at the Lives Swiss National Centre of Competence in Research (NCCR Lives).
Cognitive abilities were measured using a verbal fluency test (naming as many animals as possible in 60 seconds) and a memory test (memorising 10 words and reciting them afterwards). Physical activity was measured on a scale of 1 (“Never”) to 4 (“More than once a week”).
Earlier studies based on the correlation between physical activity and cognitive skills postulated that the former prevent the decline of the latter.
The Geneva researchers employed this data in three separate statistical models. In the first, they looked at whether physical activity predicted the change in cognitive skills over time; in the second, whether cognitive skills predicted the change in physical activity; and in the third, they tested the two possibilities bidirectionally.
“Thanks to a statistical index, we found that the second model adjusted the most precisely to the data of the participants,” says Cheval. The study demonstrates, therefore, that cognitive capacities mainly influence physical activity and not vice versa, as the literature to date had postulated.
“Obviously, it’s a virtuous cycle, since physical activity also influences our cognitive capacities. But, in light of these new findings, it does so to a lesser extent,” points out Boisgontier.
Slowing down an inevitable decline
From the age of 50, the decline in physical and cognitive abilities is inevitable.
However, these results indicate that, contrary to what was once thought, if we act first on our cognitive skills, we can slow the decline of this virtuous circle.
“This study backs up our theory that the brain has to make a real effort to get out of a sedentary lifestyle and that by working on cognitive capacities, physical activity will follow”, says Cheval by way of conclusion.
As a result of demographic change, modern societies are facing a progressively growing proportion of older adults over the next decades . Based on this development, there will be a correspondingly higher number of elderly people suffering from age-related cognitive decline and (corresponding) neurodegenerative diseases (NDs) like Parkinson’s disease (PD)  or Alzheimer’s disease (AD) . This will inevitably lead to further implications for social, occupational and health care systems [4,5,6].
Despite large inter- and intra-individual differences, mainly fluid cognitive functions (e.g., executive functions, attention, visuospatial skills, processing speed) show essential declines with age, while crystalline abilities (e.g., language or vocabulary, arithmetical skills, or general knowledge) seem to remain relatively stable and show little deteriorations, if at all [7,8,9,10].
The decrease in cognitive performance is associated with a variety of age-related brain changes, including the shrinkage in grey and white matter volume [11,12,13], region specific changes in brain connectivity [14,15], losses in brain vascularization and cerebral blood flow [16,17], higher rates of neuroinflammation [18,19], declining levels of neurotrophins [20,21], and dysregulations in neurotransmitter systems [22,23].
Those brain changes (especially volumetric changes) are most prominent in anterior regions that are particularly important for information processing and strongly associated with fluid cognitive functions [24,25,26].
Evident changes in other brain regions, such as the temporal and parietal lobe, subcortical areas (particularly the hippocampus), or cerebellum, are less distinct, but undoubtedly contribute to cognitive aging as well [9,11,13,27,28].
Based on the structural and metabolic changes, brain function is typically altered in aging individuals. Although study findings seem to be quite heterogeneous, characteristic differences in brain activation have been reported between younger and older adults.
For example, while performing cognitive tasks, older adults might display (1) a shift in activation from posterior to anterior brain regions (PASA phenomenon) [29,30], (2) higher or lower (pre-)frontal activation depending on, for instance, the difficulty and type of task [31,32,33], and (3) a reduction in hemispherical lateralization (HAROLD effect) .
These age-specific functional patterns are discussed, for example, within the ‘compensation related utilization of neural circuits’ (i.e., CRUNCH) model [32,35,36,37]. Insufficiently functioning or dysfunctional brain regions are hereby supported by usually not involved brain areas in order to maintain cognitive and behavioral performance.
Supporting this compensational view of age-related brain adaptations, other cognitive aging models, such as the STAC-r model (Scaffolding Theory of Ageing and Cognition) [7,38], integrate evidence of potential beneficial and detrimental factors, such as lifestyle factors, social/intellectual engagement, or exercise approaches, influencing the efficacy of compensational networks.
The variety of those factors might help to explain individual differences and heterogeneous study findings. Furthermore, such models might contribute to develop effective multi-domain lifestyle and intervention strategies to maintain cognitive performance and brain health up to old age.
A variety of non-pharmaceutical intervention concepts have been developed and evaluated to attenuate age-related cognitive decline or to even improve cognitive performance in older adults. Apart from different lifestyle approaches (e.g., nutrition or education), particularly physical exercise [39,40,41,42] and cognitive training [43,44,45,46] have been shown to benefit cognitive and brain health [38,47,48].
Physical exercise appears to induce physiological and metabolic changes that in turn facilitate particular cognitive functions (specifically executive functions) through brain structural and functional adaptations [39,40,41,49,50].
In contrast, cognitive training appears to benefit the trained cognitive abilities almost exclusively with very limited transfer to untrained domains [44,45,51,52]. Thus, both physical and cognitive training, vary regarding their effects on cognitive and brain function [53,54,55].
Both forms of intervention, however, seem to depend on, for example, training intensity, duration, frequency, and type of exercise. Potential moderators of training efficacy, however, still need to be determined more precisely [40,44,45,55,56,57].
Based on the individual beneficial effects of physical and cognitive training, combined interventions have been developed to maximize training efficiency and cognitive benefits .
So far, review articles concluded that combined physical and cognitive training interventions show larger effects on cognitive functions than single-domain physical or cognitive training and even subsequently applied physical and cognitive training [59,60,61].
In this vein, exergaming has become an interesting approach. Exergaming, as a novel form of exercise, likewise combines physical and cognitive exercise in an interactive digital, augmented, or virtual game-like environment.
Commercial exergame systems, such as the Nintendo Wii, Xbox Kinect, or Dance Dance Revolution have already been demonstrated to be equally demanding as moderate physical exercise [62,63,64,65].
Furthermore, playing video games seems to be beneficial for cognitive functions and therefore might substitute (non-)computerized cognitive training [33,66].
Thus, combining physical exercise and gaming in exergames might be a promising approach to facilitate cognitive and brain functioning in older adults.
A variety of systems have been utilized for exergame interventions, all of which were summarized to have equal or superior benefits on cognitive functions than single-domain and combined physical-cognitive training [67,68].
Exergames have been discussed to amplify the effects of physical exercise by guiding neuroplastic changes via additional cognitive exercise [69,70,71]. However, literature is lacking an updated and comprehensive systematic review on cognitive benefits and the underlying neurophysiological mechanisms of the complementary physical-cognitive training effects of exergaming in healthy older adults.
Therefore, we performed an extensive systematic literature search to gather evidence on intervention effects of exergaming on cognitive domains with a particular focus on neurophysiological outcomes.
We will confer our findings with respect to the current literature on physical, cognitive, and combined exercise interventions. Moreover, we will discuss potential neurobiological mechanisms underlying exergaming effects and methodological considerations for prospect exergame intervention studies.
The intention of this systematic review was to present a comprehensive overview of the efficiency and underlying neurophysiological processes of exergame training in older adults. We found an overall small and strongly varying positive influence of exergaming on cognitive and brain function in healthy older adults.
Benefits on individual cognitive domains showed no consistency. Besides these heterogeneous findings, studies that compared exergaming to traditional types of exercise, such as cardiovascular exercise, found similar or slightly superior effects of exergaming on executive functions but not on other cognitive domains.
This might be an indicator that exergaming is a promising approach to preserve and facilitate cognitive and brain health in healthy older adults. Based on the variety of exergame systems and corresponding games, exergaming might be a useful alternative to traditional exercise to further motivate (older) people to regularly engage in physical activity.
However, further research is urgently needed to determine potential influencing factors that contribute to intervention efficacy in order to understand the underlying mechanisms and to apply tailored intervention for particular target groups and individual needs
University of Geneva
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