It is well known that exercise is beneficial to many body systems including neuroprotective effects which not only protect but imporve memory and cognition. But can you be too old or frail to reap the rewards of the cognitive protective and boosting effects of exercise?
We know that with regular exercise people living with even severe levels of frailty can improve their physical performance and different components of their frailty. But there is less known about the effect of physical exercise on the cognitive of older people. A new systematic review has been published with this in mind and has the aim of analysing the effects of physical exercise on cognition of community dwelling older adults living with frailty.
Cognitive frailty is not a new concept and is part and parcel of the multi-system dysregulation of the frailty process which is underpinned by chronic low levels of inflammation and disruption of cellular processes which effect homeostasis. The determining factors for the characterization of cognitive frailty are interrelated with the deficits resulting from physical frailty, social determinants of health, decreased level of physical activity, diet, reduction in
social contact, and reduction in domestic activities and health practices.
The hypothesis is, that just with physical aspects of frailty, through the use of exercise the cognitive frailty process can be reversed and some studies have shown these effects. The difficulty is that these studies have been small scale and therefore still inconclusive. There has also not been a systematic review directly focussing on this topic and that is where this systematic review comes in.
This systematic review was pre-registered in PROSPERO and the review protocol adhered to PRISMA. The search strategy is published in full with 9 databases being searched for articles to be included within the review. According to The Cochrane Collaboration and several other reviews, including more than 4 or 5 databases probably doesn’t alter the outcomes of the systematic review but the thoroughness of the authors should be commended.
The search strategies for each database was included in full within the appendix and an example of the search used for Cochrane Database is below.
Final String: ((frailty OR “frail elderly”) AND aged AND (exercise OR rehabilitation) AND cognition) in Title Abstract Keyword – (Word variations have been searched).
As with all systematic reviews which adhere to PRISMA there were two main researchers who were deciding which articles to include within the review and a third to help reach consensus if there was disagreement about the inclusion of an article.
Eligibility and study selection criteria was published in full. Only RCTs which used physical exercise as an intervention in community dwelling older adults who were older than 60 years old with proven frailty and cognitive impairment were included within the review. What is great to see is that to be considered as physical activity the training protocol had to be planned, systematic, structured, purposeful, involve repetitive movements and be supervised by a trained professional. Too often in systematic reviews or research involving exercise the fundamental principles of training are not adhered to which immidiately limits the certainty of the results.
Looking at the exclusion criteria it is interesting to see that studies which used exercise based on Tai Chi was excluded from the review. Tai Chi is very popular with healthcare professionals working with older people because of it’s benefits on balance but it has also been suggested that it has memory protective effects. That being said often Tai Chi and similar yoga and dance based exercise programmes for older people are sub-therapeutic as do not follow the principles of training or are not dosed at the correct intensity on an individual bases. This is likely the reason this type of exercise was excluded.
It is also worth pointing out that research involving people living with neurodegenerative disorders was excluded from the review. This makes sense as they have an underlying pathology affective memory (this includes Alzheimers Dementia).
Frailty was assessed using Fried’s Phenotype, Rockwood Frailty Index, the Edmonton Frailty Scale and the modified Physical Performance Test. There were no conflicts of interest declared and the research was funded by a Brazilian research grant. Risk of bias was assessed using the PEDRO scale. The MMSE was the most commonly used cognitive test used with Trial Making Test Forms A & B andDigit Span Tests the next most commonly used tests. In total 15 other different tests were used by this includes different versions for language.
In total the review includes a total of 665 participants with mean ages between 68.7 to 80.3 years of age. There were more women included in the trial all together .
Clinical Importance and Take Home Lessons
In summary it can be said that exercise training in people living with frailty provides improvements to global cognitive function, sequencing mental flexibility and visuomotor skills. It is unlikely to provide any benefit to processing speed and it is difficult to draw definitive conclusions about which type of physical exercise promotes the biggest benefits in protective cognitive abilities.
Looking at the breakdown of the different types of exercise used within the articles included within the systematic review the biggest cognitive gains are probably related to the aerobic compontents. This also follows a logical biological answer in that aerobic exercise (more than other forms of exercise) improves cerebral blood flow and facilitates neurogenesis leading to improved cognitive function. Clearly this is a reductionist explanation but follows some logic at least.
There were large differences in the total amount (in minutes) of exercise per week within the included articles. All included exercise plans improved cognitive abilities to some degree but aim for a minimum of 150 minutes per week and ideally 180+ to get the most well rounded cognitive gains.
Social interaction, although not a central part of the research protocols, provides important gains to older adults living with frailty. The sense of routine, the social interaction, and the commitment of a goal provide substantial gains on their own and although not directly measures would have contirbuted to the cognitive gains.