The researchers stared with 2 mains facts:
- Gray matter volume shrinks with age, often leading to cognitive decline.
- Physical exercise seems to be neuro-protector (see our previous post: Fitter bodies = fitter brains. True at all ages?)
They asked 2 questions:
- Can physical activity assessed earlier predict gray matter volume 9 years later?
- Is greater gray matter volume associated with reduced risks of developing cognitive impairment?
- 299 participants, mean age: 78, 182 female.
- Physical activity was assessed in 1988–1989 (baseline) = total number of blocks walked over 1 week.
- Cognitive functions were assessed in 1998–1999 (all participants were cognitively normal) and 3–4 years later (116 participants were diagnosed with dementia or mild cognitive impairment, MCI).
- High-resolution MRI scans of the participants’ brains were taken in 1998–1999 (9 years after physical activity was assessed).
- Greater amounts of physical activity (walking distance) predicted greater gray matter volume 9 years later: the longer the distance people used to walk, the larger their brain volume.
- This effect was observed mostly in the prefrontal and temporal regions of the brain, including in the hippocampus (a region critical for forming new memories).
- The effect appeared only when walking long distances (6–9 miles a week).
- The effect was associated with lower risk of developing dementia or MCI.
Limitations of the study: First, gray matter volume could not be measured at the beginning of the study. Thus it is possible that physical activity was not the factor causing the increase of gray matter. Maybe people who ended up with bigger brains at the end of the 9 years study also started with bigger brains, for whatever reason.
Second, participants were not randomly assigned to a physical exercise group and a control group. It is thus not possible to conclude that physical activity per se CAUSED greater brain volume in this particular study. Note however that such a causal relationship has been observed in other studies.
Strengths of the study: The sample size was good and the follow-up period long enough (13 years) to suggest that exercising now matters for later brain fitness.
The results confirm that physical exercise is good for the brain! Aerobic activity may increase the growth of new neurons, the connections between neurons and the blood vessels nourishing the brain.
Reference: K.I. Erickson, C.A. Raji, O.L. Lopez, J.T. Becker, C. Rosano, A.B. Newman, H.M. Gach, P.M. Thompson, A.J. Ho, and L.H. Kuller (2010). Physical activity predicts gray matter volume in late adulthood: The Cardiovascular Health Study. Neurology ; 75: 1415.