The study involved 120 healthy older adults (60-79) from Shanghai, who were randomly assigned to one of four groups: one that participated in three sessions of tai chi every week for 40 weeks; another that instead had ‘social interaction’ sessions (‘lively discussions’); another in which participants engaged in walking around a track; and a non-intervention group included as a control. Brain scans were taken before and after the 40-week intervention, and cognitive testing took place at 20 weeks as well as these times.
Compared to those who received no intervention, both those who participated in tai chi, and those who participated in the social sessions, showed significant increases in brain volume and on some cognitive measures. However, the tai chi group showed improvement on more cognitive tests than the social group (on the Mattis Dementia Rating Scale, the Trailmaking Tests, delayed recognition on the Auditory Verbal Learning Test, and verbal fluency for animals vs verbal fluency and positive trends only on Trails A and the Auditory test).
Surprisingly, there were no such significant effects from the walking intervention, which involved 30 minutes of brisk walking around a 400m circular track, sandwiched by 10 minutes of warm-up and 10 minutes cool-down exercises. This took place in the same park as the tai chi sessions (which similarly included 20 minutes of warm-up exercises, 20 minutes of tai chi, and 10 minutes of cool-down exercises).
This finding is inconsistent with other research, but the answer seems to lie in individual differences — specifically, speed of walking. Faster walkers showed significantly better performance on the Stroop test, and on delayed recall and recognition on the Auditory Verbal Learning Test. It should be noted that, unlike some studies in which participants were encouraged to reach heart-rate targets, participants in this study were simply told to walk at their own speed. This finding, then, would seem to support the view that brisk walking is needed to reap good health and cognitive benefits (which shouldn’t put anyone off — anything is better than nothing! and speed is likely to come with practice, if that’s your aim).
It should also be noted that this population has generally high rates of walking. It is likely, then, that the additional walking in these sessions did not add a great deal to their existing behavior.
There is a caveat to the strongly positive effects of tai chi: this group showed lower cognitive performance at baseline. This was because the group randomly received more individuals with very low scores (8 compared with 5 in the other groups).
The study is, of course, quite a small one, and a larger study is required to confirm these results.
One final note: the relative differences in enjoyment were not explicitly investigated, but the researchers did note that the social group, who initially were given topics to discuss in their hour-long sessions, then decided to select and organize their own discussions, and have continued to do so for two years following the end of the study. It would have been nice if the researchers had re-tested participants at that point.
Mortimer, J.A. et al. 2012. Changes in Brain Volume and Cognition in a Randomized Trial of Exercise and Social Interaction in a Community-Based Sample of Non-Demented Chinese Elders. Journal of Alzheimer's Disease, 30 (4), 757-766.
Full text available at http://health.usf.edu/nocms/publicaffairs/now/pdfs/JAD_Mortimer_30%28201...