A number of studies have found that physical exercise can help delay the onset of dementia, however the ability of exercise to slow the decline once dementia has set in is a more equivocal question. A large new study answers this question in the negative.
The study involved 494 people with mild-to-moderate dementia (average age 77; 61% male), of whom 329 were randomly assigned to a four-month aerobic and strength exercise programme and 165 were assigned to usual care. The exercise program was personalized, and involved two 60-90 minute gym sessions every week, plus a further hour at home. Nearly two-thirds of the exercise group attended more than three-quarters of the gym sessions.
While the exercise group did get physically fitter, their cognitive fitness (as measured by ADAS-cog score) actually worsened slightly.
The researchers emphasize that this was a specialized and intense exercise program, and in no way should it be taken to mean that gentle exercise, which is good for dementia sufferers, should be avoided.
 Dementia And Physical Activity (DAPA) trial of moderate to high intensity exercise training for people with dementia: randomised controlled trial. BMJ [Internet]. 2018 ;361:k1675. Available from: https://www.bmj.com/content/361/bmj.k1675