Physical Activity Interventions
It has been uncertain whether changes in physical activity levels affect dementia incidence, but meta-analyses have clearly shown that aerobic physical activities that improve cardiorespiratory fitness enhance cognitive performance in initially sedentary older adults. Several recent trials have been based on the possibility that increases in cardiovascular fitness may not be essential for cognitive benefits, and thus investigated whether other forms of physical activity may also enhance cognition in old age.
Two recent trials examined whether regular engagement in virtual-reality enhanced exercise ('exergaming') that combines physical activities with computer-simulated environments affects cognitive performance in older age. In one trial,[14•] an intervention group (n = 38; mean age = 76 years) was cycling in an interactive virtual environment ('cybercycling') for 45 min up to five times per week for 2 months. The control group (n = 41; mean age = 82 years) was cycling without the virtual environment. Outcome measures were assessed before training and immediately after the intervention. Significantly larger improvements for the cybercycling group than for the control group were observed on measures of executive functioning, but not on measures of attention, verbal fluency, episodic memory, and visuo-spatial memory. In the second trial,[15] an intervention group (n = 15; mean age = 73 years) was playing Nintendo Wii games (e.g., Wii Tennis and Wii Boxing) during two 1-h sessions per week over a period of 12 weeks, and a no-contact group served as control (n = 15; mean age = 73 years). Results included training-related effects on measures of executive functioning and perceptual speed. These findings should, however, be interpreted with caution because the control group did not receive any placebo condition. Nevertheless, these trials demonstrated the feasibility and advantages of virtual-reality enhanced exercise, which is easy and more fun to perform than exercising without games, so that people will do exergaming more often than ordinary physical exercise.
The effects of strength training and aerobic exercise on executive function in older women with mild cognitive impairments were evaluated in one trial[16••]. Individuals in the strength training (n = 28; mean age = 74 years) and aerobic fitness (walking; n = 30; mean age = 76 years) group trained twice weekly for 6 months. The control group (n = 28; mean age = 75 years) was performing balance and stretching exercises. Compared with the control group, strength training resulted in improved performance on the Stroop task and on an associative memory task. The aerobic fitness group did not display any training-related effects. This study highlighted the importance of strength training, which may be at least as beneficial for cognitive performance as aerobic fitness training. Notably, effects were also observed in individuals with lower cognitive performance, which is consistent with results from a study investigating the effects of physical activity on cognition in individuals with mild cognitive impairment using a multicomponent exercise intervention.[17•] Participants in the intervention group (n = 25; mean age = 75 years) performed aerobic exercises, strength training, and postural balance training in twice-weekly 90-min sessions, for a total of 80 times during 12 months. Individuals in a control group (n = 25; mean age = 75 years) attended three education classes during the intervention year. Training-related improvement was observed on the mini-mental state examination, immediate recall, and verbal fluency tasks, but not on delayed recall, psychomotor speed, and the Stroop task.
The effects of physical exercise on cognition in low-performing individuals provide hopes that such intervention may reduce conversion to clinical dementia. This was directly studied in a RCT of Tai Chi training[18••]. The intervention group (n = 171; mean age = 77 years) was compared with a stretching and toning control group (n = 218; mean age = 78 years). Participants were training for at least 30 min per day and at least 3 days per week over a period of 12 months. Results showed that deterioration to clinical dementia as diagnosed by DSM-IV at the posttest (12-month) assessment tended to be more frequent in the control group (17%) than in the intervention group (4%). Training-related effects on cognitive outcome variables were, however, not observed, limiting the conclusions that can be drawn from this trial. Nevertheless, this study is important because it directly addresses effects of changes in physical activity on the incidence of dementia, and provides some preliminary support suggesting that such lifestyle change may reduce incidence of dementia. In our view, future research must continue this line of work and include dementia diagnosis as an outcome, as well as consider several forms of physical activities as useful targets for intervention.