In the lat­est issue of Neu­rol­ogy a study by Erick­son et al. (2010) sug­gests that walk­ing reg­u­larly can increase brain vol­ume and reduce the risks of devel­op­ing cog­ni­tive impairment.

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?

The study:

• 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).

The results

• 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.

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