Physical exercise and mental exercise are both beneficial for the brain. Each can improve brain functions and decrease risks of cognitive decline over time. This raises the question of their comparative and combined effects: Is one better than the other? Are their benefits additive? A recent study suggests that their benefits are equivalent and not additive. However the results seem as inconclusive as the results of the few other studies that have tried to answer these questions so far.
The study involved 126 older adults (mean age of 73.4) with cognitive complaints, that is who felt their memory and thinking skills had declined in the recent past (Barnes, 2013). Participants were divided onto 4 groups:
1. Computerized brain training (to enhance visual and auditory processing speed) + aerobic exercise
2. Watching educational DVD + aerobic exercise
3. Computerized brain training + stretching and toning
4. Watching educational DVD + stretching and toning
As you can see all groups participated in a mental activity (1h three times a week) and a physical activity (1h three times a week). What differed between them was the type of activity performed: Watching educational DVD was a control group for brain training, that is it was not expected to bring benefits (or much less). In the same way, stretching and toning was a control for aerobic exercise.
A global cognitive score was obtained before and after the intervention for all participants, using tests of verbal learning and memory, verbal fluency, processing speed, executive and visuospatial functions and mental flexibility. The four groups had similar scores to start with.
Results showed that all 4 groups global cognitive functioning improved after the 12 weeks intervention.
The comparisons between groups 1 and 3 and between groups 2 and 4 showed that both mental exercise and physical exercise brought cognitive benefits, and this to the same extent.
Surprisingly the comparisons between groups 1 and 2 and between groups 3 and 4 (actual interventions versus control groups) showed that the control activities (watching DVD and stretching and toning) triggered the same benefits as the intervention activities (brain training and aerobic). This is not what previous studies have shown. A larger benefit of brain training or aerobic training is usually observed compared to merely watching educational DVD or stretching and toning. Further analysis on a small subgroup of participants who had the most memory difficulties nevertheless showed the usual extra benefit of brain training over educational videos.
The authors offer two possible explanations for the results. One is that all the participants got better at the cognitive tests because of a practice effect (remember that they were tested before and after the study). Another explanation is that for this population, that is for older adults with memory complaints, it is not so much the type of activity that matters but the mere fact of being active.
In sum, these results are inconclusive. This is also the case for the very few other studies that have so far tried to compare the benefits of physical and mental activity.
A 2006 study conducted with 375 healthy older adults between the ages of 75 and 93 compared the effects of mental, physical and combined training (Oswald et al., 2006). The brain training was done using paper and pencil tasks. The physical training targeted balance, flexibility and motor coordination. Results showed cognitive gains only following mental and combined training.
A smaller 2013 study with 122 healthy adults over 80 compared 4 groups: brain training (using CogniFit computerized exercises 3 times a week for 16 weeks), physical training (aerobic exercise 3 times a week for 16 weeks), combined training, and control (book reading at home and 1h discussions once a week) (Shatil, 2013). Cognitive gains were observed only following mental and combined training. The author concludes that either the physical training intervention was not long enough or too mild to yield benefits or that cognitive training is the main agent for cognitive changes.
In conclusion, it is too early to tell whether brain training and physical training have comparable effects or whether their effects combine in some ways. The bulk of the research so far nevertheless strongly suggests that they both have measurable positive effects on cognition.
Aerobic physical exercise can improve attention and executive functions as well as reverse brain volume loss. It usually takes 6 months or so to see such benefits. Brain training studies show steady cognitive gains after 10 to 15 weeks of training, although the gains do not generally transfer to many untrained tasks. Population studies have also repeatedly shown that people who participate in mentally stimulating leisure activities throughout their life have healthier brains, higher cognitive functioning and lower risks of dementia over the long run.
Barnes, D. E., et al. (2013). The Mental Activity and eXercise (MAX) Trial: A Randomized Controlled Trial to Enhance Cognitive Function in Older Adults. JAMA Internal Medicine, 1-8. doi:10.1001/jamainternmed.2013.189.
Oswald, W., et al. (2006). Differential effects of single versus combined cognitive and physical training with older adults: The SimA study in a5-year perspective. European Journal of Ageing, 3, 179-192.
Shatil, E. (2013). Does combined cognitive training and physical activity training enhance cognitive abilities more than either alone? Frontiers in Aging Neuroscience, doi: 10.3389/fnagi.2013.00008.