The results from animal models have indicated that physical activity might slow cognitive decline in dementia. However, systematic reviews of randomised trials have shown conflicting results with one review showing a benefit on cognitive decline and another recent review showing no effect. These reviews included small trials of low methodological quality. The present trial was commissioned to provide reliable evidence on the effects of exercise on cognitive decline in people with dementia.
The Dementia And Physical Activity (DAPA) trial was a multicentre, pragmatic, investigator masked, randomised controlled trial. Random allocation was 2:1 in favour of the exercise arm. Eligible participants had mild to moderate dementia with a diagnosis in accordance with the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) and a standardised Mini Mental State Examination (MMSE) of greater than 10. Participants also needed to be able to sit on a chair and walk 10 feet (3.05m) without assistance.
The exercise arm was delivered by physiotherapists and exercise assistants and consisted of a four month twice weekly 60-90 minute sessions supplemented by a one hour session of home-based exercise. The exercise programme was individualised according to the participant’s level of fitness and health status and the exercises included aerobic activity using a static cycle and strength training using free weights. Following the four month period of supervised exercise participants were requested to continue exercising at home for a total of 150 minutes per week. The control arm only received brief advice on physical activity as part of their clinical assessment.
The primary outcome was the Alzheimer disease assessment scale cognitive subscale (ADAS-cog) at 12 months. Secondary outcomes measured at 6 and 12 months included the Bristol activity of daily living index, the neuropsychiatric index, the three level version of the EQ-5D quality of life measure, the quality of life Alzheimer’s disease scale and the ADAS praxis, language and memory subscales (the ADAS-cog was also measured as a secondary outcome at 6 months). The assessors were blinded to the randomised treatment allocation. All analyses were according to intention-to-treat principles.
A total of 2,929 patients were screened with 1,847 potentially eligible and invited to participate and a total of 494 were randomised (329 to the exercise arm and 165 to the control group). The two groups were well matched according to the baseline measures assessed. For the exercise group, the total weight lifted and the duration of high intensity aerobic activity improved across the sessions. A 6-minute walk test was undertaken to assess physical fitness and at 6 weeks the total distance covered had improved significantly (95% confidence interval 11.6 m to 24.6 m; P<0.001). The majority (88%) of participants in the exercise arm reported continuing with the exercise programme after the end of the 4 month supervised programme.
For the main outcome, cognitive impairment declined in both arms during the 12 months follow up with ADAS-cog scores higher (higher scores indicate worse cognition) in the exercise arm at 12 months (adjusted mean difference −1.4, 95% confidence interval −2.6 to −0.2). No difference was observed in any of the secondary outcomes measured.
The authors conclude that a four month aerobic and strengthening exercise programme of moderate to high intensity added to usual care does not slow cognitive decline in people with mild to moderate dementia. The exercise programme improved physical fitness in the short term and the results suggest the possibility that exercise might worsen cognition in people with dementia.
The full report of the study can be read here.