Physical Exercise and Brain Health

JUN 26, 2008

By: Dr. Pascale Michelon

Have you heard of or read John Ratey’s book “Spark: The Rev­o­lu­tion­ary New Sci­ence of Exer­cise and The Brain”? Accord­ing to Har­vard Psy­chi­a­try Pro­fes­sor John Ratey noth­ing beats exer­cise for pro­mot­ing brain heath.

I am sure you have also heard that exer­cis­ing your mind pro­motes brain health.

What is the con­nec­tion between phys­i­cal and men­tal exer­cises? Do they have addi­tive effects on brain health? Are they redundant?

Let’s start by review­ing what we know about the effects of phys­i­cal exer­cise on the brain.

The effect of phys­i­cal exer­cise on cog­ni­tive performance

Early stud­ies com­pared groups of peo­ple who exer­cised to groups of peo­ple who did not exer­cise much. Results showed that peo­ple who exer­cised usu­ally had bet­ter per­for­mance in a range of cog­ni­tive tasks com­pared to non-exercisers.

Lau­rin and col­leagues (2001) even sug­gested that mod­er­ate and high lev­els of phys­i­cal activ­ity were asso­ci­ated with lower risk for Alzheimer’s dis­ease and other dementias.

The prob­lem with these stud­ies is that the exer­cis­ers and the non-exercisers may dif­fer on other fac­tors than just exer­cise. The advan­tage that exer­ciser show may not come from exer­cis­ing but from other fac­tors such as more resources, bet­ter brain health to start with, bet­ter diet, etc.

The solu­tion to this prob­lem is to ran­domly assigned peo­ple to either an aer­o­bic train­ing group or a con­trol group. If the exer­ciser group and the non-exerciser group are very sim­i­lar to start with and if the exer­ciser group shows less decline or bet­ter per­for­mance over time than the non-exerciser group, then one can con­clude that phys­i­cal exer­cise is ben­e­fi­cial for brain health.

In 2003, Col­combe and Kramer, ana­lyzed the results of 18 sci­en­tific stud­ies pub­lished between 2000 and 2001 that were con­ducted in the way described above.

The results of this meta-analysis clearly showed that fit­ness train­ing increases cog­ni­tive per­for­mance in healthy adults between the ages of 55 and 80.

Another meta-analysis pub­lished in 2004 by Heyn and col­leagues shows sim­i­lar ben­e­fi­cial effects of fit­ness train­ing on peo­ple over 65 years old who had cog­ni­tive impair­ment or dementia.

What is the effect of fit­ness train­ing on the brain itself?

Research with ani­mals has shown that in mice, increased aer­o­bic fit­ness (run­ning) can increase the num­ber of new cells formed in the hip­pocam­pus (the hip­pocam­pus is cru­cial for learn­ing and mem­ory). Increased exer­cise also has a ben­e­fi­cial effect on mice’s vas­cu­lar system.

Only one study has used brain imag­ing to look at the effect of fit­ness on the human brain. In 2006, Col­combe and col­leagues ran­domly assigned 59 older adults to either a car­dio­vas­cu­lar exer­cise group, or a non­aer­o­bic exer­cise con­trol group (stretch­ing and ton­ing exer­cise). Par­tic­i­pants exer­cised 3h per week for 6 months. Col­combe et al. scanned the par­tic­i­pants’ brains before and after the train­ing period.

After 6 months, the brain vol­ume of the aer­o­bic exer­cis­ing group increased in sev­eral areas com­pared to the other group. Vol­ume increase occurred prin­ci­pally in frontal and tem­po­ral areas of the brain involved in exec­u­tive con­trol and mem­ory processes. The authors do not know what under­ly­ing cel­lu­lar changes might have caused these vol­ume changes. How­ever they sus­pect, based on ani­mal research, that vol­ume changes may be due to an increased num­ber of blood ves­sels and an increased num­ber of con­nec­tions between neurons.

How does phys­i­cal exer­cise com­pare to men­tal exercise?

Very few stud­ies have tried to com­pare the effect of phys­i­cal exer­cise and men­tal exer­cise on cog­ni­tive performance.

When look­ing at each domain of research one notices the fol­low­ing differences:

- The effects of cog­ni­tive or men­tal exer­cise on per­for­mance seem to be very task spe­cific, that is trained tasks ben­e­fit from train­ing but the ben­e­fits do not trans­fer very well to tasks in which one was not trained.

- The effects of phys­i­cal exer­cise on per­for­mance seem broader. How­ever they do not gen­er­al­ize to all tasks. They ben­e­fit mostly tasks that involve executive-control com­po­nents (that is, tasks that require plan­ning, work­ing mem­ory, mul­ti­task­ing, resis­tance to distraction).

To my knowl­edge only one study tried to directly com­pare cog­ni­tive and fit­ness training:

Fabre and col­leagues, in 1999, ran­domly assigned sub­jects to 4 groups: an aer­o­bic train­ing group (walk­ing or run­ning for 2 h per week for 2 months), a mem­ory train­ing group (one 90 min ses­sion a week for 2 months), a com­bined aer­o­bic and men­tal train­ing group, or a con­trol group (no training).

Results showed that com­pared to the con­trol group, the mem­ory per­for­mance of all 3 groups increased. The com­bined group showed greater increase than the other 2 train­ing groups.

This sug­gests that the effects of cog­ni­tive and fit­ness train­ing may be addi­tive. How­ever this study involved only 8 par­tic­i­pants per group! More research is clearly needed before any­thing can be safely concluded.

In the mean­time let’s play it safe and com­bine fit­ness and cog­ni­tive train­ing for bet­ter brain health.