Physical activity and cognitive function in adults with multiple sclerosis: an integrative review.
Janet D Morrison, Lori Mayer
PMID 27764974WHAT IT FOUND
In adults with MS, more active or fitter people had better scores on cognitive tests of processing speed, memory and executive function.
Exercise trials were mixed, so this does not show exercise improves cognition.
Key findings
01Across 19 studies with 1,007 adults with MS, cross-sectional studies reported positive links between physical activity or fitness and cognitive processing speed, verbal learning and memory, and executive function.
02The review reported no change in cognition that the authors counted as significant in two intervention studies and positive cognitive outcomes in eight more recent studies.
03The review states that the evidence does not establish causation and that strong evidence for physical activity improving cognition in MS is lacking.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only 19 studies were included, and unpublished studies and poor-quality studies were excluded, which may introduce bias. Self-report cognitive measures were excluded, so the review does not cover other ways of assessing cognition. Many intervention studies had small samples, with sizes from 20 to 95, and reported attrition varied from 4% to 17%; some studies did not report dropouts. Exercise prescriptions varied widely in mode, frequency and duration, and only four studies documented intensity, so it is unclear what dose might matter. The review relied on clinical cognitive tests, and the authors question whether better test scores translate to everyday functions such as driving or employment. Depression and fatigue can affect cognitive test performance, but their contribution was not fully separated. Cross-sectional links cannot show that physical activity causes better cognition; the reverse, or a person's level of disability, could explain them.
The easy way to misread this
Do not conclude that exercise improves cognition in MS. The review found associations in cross-sectional studies and mixed results from exercise trials, and it states that strong evidence for cognitive benefit is lacking.