Build Your Cognitive Reserve: An Interview with Dr. Yaakov Stern

Dr. Yaakov Stern is the Divi­sion Leader of the Cog­ni­tive Neu­ro­science Divi­sion of the Sergievsky Cen­ter, and Pro­fes­sor of Clin­i­cal Neu­ropsy­chol­o­gy, at the Col­lege of Physi­cians and Sur­geons of Colum­bia Uni­ver­si­ty, New York. Alvaro Fer­nan­dez inter­views him here as part of our research for The Sharp­Brains Guide to Brain Fit­ness book.

Dr. Stern is one of the lead­ing researchers of the Cog­ni­tive Reserve the­o­ry, which aims to explain why some indi­vid­u­als with full Alzheimer’s pathol­o­gy (accu­mu­la­tion of plaques and tan­gles in their brains) can keep nor­mal lives until they die, while oth­ers with the same amount of plaques and tan­gles dis­play the severe symp­toms we asso­ciate with Alzheimer’s Dis­ease. He has pub­lished dozens of peer-reviewed sci­en­tif­ic papers on the subject.

The con­cept of a Cog­ni­tive Reserve has been around since 1989, when a post mortem analy­sis of 137 peo­ple with Alzheimer’s Dis­ease showed that some patients exhib­it­ed few­er clin­i­cal symp­toms than their actu­al pathol­o­gy sug­gest­ed. These patients also showed high­er brain weights and greater num­ber of neu­rons when com­pared to age-matched con­trols. The inves­ti­ga­tors hypoth­e­sized that the patients had a larg­er “reserve” of neu­rons and abil­i­ties that enable them to off­set the loss­es caused by Alzheimer’s. Since then, the con­cept of Cog­ni­tive Reserve has been defined as the abil­i­ty of an indi­vid­ual to tol­er­ate pro­gres­sive brain pathol­o­gy with­out demon­strat­ing clin­i­cal cog­ni­tive symptoms.

Key take-aways

• Life­time expe­ri­ences, like edu­ca­tion, engag­ing occu­pa­tion, and leisure activ­i­ties, have been shown to have a major influ­ence on how we age, specif­i­cal­ly on whether we will devel­op Alzheimer’s symp­toms or not.
• This is so because stim­u­lat­ing activ­i­ties, ide­al­ly com­bin­ing phys­i­cal exer­cise, learn­ing and social inter­ac­tion, help us build a Cog­ni­tive Reserve to pro­tect us.
• The ear­li­er we start build­ing our Reserve, the bet­ter; but it is nev­er too late to start. And, the more activ­i­ties, the bet­ter: the effect is cumulative.

The Cog­ni­tive Reserve

Alvaro Fer­nan­dez (AF): Dear Dr. Stern, it is a plea­sure to have you here. Let me first ask you this: the impli­ca­tions of your research are pret­ty broad, pre­sent­ing major impli­ca­tions across sec­tors and age groups. What has been the most unex­pect­ed reac­tion so far?

YS: well…I was pret­ty sur­prised when, years ago, a reporter from Sev­en­teen mag­a­zine request­ed an inter­view. I was real­ly curi­ous to learn why she felt that her read­ers would be inter­est­ed in stud­ies about demen­tia. What she told me showed a deep under­stand­ing and insight: she want­ed to moti­vate chil­dren to stay in school. She under­stood that ear­ly social inter­ven­tions could be very pow­er­ful for build­ing reserve and pre­vent­ing dementia.

AF: Very insightful…let’s now fast for­ward, say, 60 years from our high-school years, and sup­pose that per­sons A and B both tech­ni­cal­ly have Alzheimer’s (plaques and tan­gles appear in the brain), but only A is show­ing the dis­ease symp­toms. What may explain this discrepancy?

YS: Indi­vid­u­als who lead men­tal­ly stim­u­lat­ing lives, through edu­ca­tion, occu­pa­tion and leisure activ­i­ties, have reduced risk of devel­op­ing Alzheimer’s. Stud­ies sug­gest that they have 35–40% less risk of man­i­fest­ing the dis­ease. The pathol­o­gy will still occur, but they are able to cope with it bet­ter. Some won’t ever be diag­nosed with Alzheimer’s because they don’t present any symp­toms. In stud­ies that fol­low healthy elders over time and then get autop­sies, up to 20% of peo­ple who did not present any sig­nif­i­cant prob­lem in the dai­ly lives have full blown Alzheimer’s pathol­o­gy in their brains.

AF: What exact­ly may be going on in the brain that pro­vides that lev­el of protection?

YS: There are two ideas that are com­ple­men­tary. One idea (called Brain Reserve by researchers) pos­tu­lates that some indi­vid­u­als have a greater num­ber of neu­rons and synaps­es, and that some­how those extra struc­tures pro­vide a lev­el of pro­tec­tion. In a sense, we have more “hard­ware”, pro­vid­ing a pas­sive pro­tec­tion against the attacks of Alzheimer’s. The oth­er the­o­ry (called Cog­ni­tive Reserve) empha­sizes the build­ing of new capa­bil­i­ties, how peo­ple can per­form tasks bet­ter through prac­tice, and how these skills become so well learned that they are not too easy to unlearn. Like devel­op­ing new and refined “soft­ware”.

AF: But, both seem to go hand in hand, cor­rect? Neu­ro­plas­tic­i­ty means that what you call “hard­ware” and “soft­ware” are two sides of the same coin and they influ­ence each oth­er, right?

YS: Cor­rect. So these days we don’t make a sharp dis­tinc­tion, and are con­duct­ing more neu­roimag­ing stud­ies to bet­ter under­stand the rela­tion­ship between both.

Build­ing Your Cog­ni­tive Reserve

AF: So our goal is to build that Reserve of neu­rons, synaps­es, and skills. How can we do that? What defines “men­tal­ly stim­u­lat­ing activ­i­ties” or good “brain exercise”?

YS: In sum­ma­ry, we could say that “stim­u­la­tion” con­sists of engag­ing in activ­i­ties. In our research almost all activ­i­ties are seen to con­tribute to reserve. Some have chal­leng­ing lev­els of cog­ni­tive com­plex­i­ty, and some have inter­per­son­al or phys­i­cal demands. In ani­mal stud­ies, expo­sure to an enriched envi­ron­ment or increased phys­i­cal activ­i­ty result in increased neu­ro­ge­n­e­sis (the cre­ation of new neu­rons). You can get that stim­u­la­tion through edu­ca­tion and/ or your occu­pa­tion. There is clear research show­ing how those two ele­ments reduce the risk. Now, what is very excit­ing is that, no mat­ter one’s age, edu­ca­tion and occu­pa­tion, our lev­el of par­tic­i­pa­tion in leisure activ­i­ties has a sig­nif­i­cant and cumu­la­tive effect. A key mes­sage here is that dif­fer­ent activ­i­ties have inde­pen­dent, syn­er­gis­tic, con­tri­bu­tions, which means the more things you do and the ear­li­er you start, the bet­ter. But you are nev­er stuck: bet­ter late than never.

AF: Can you give us some exam­ples of those leisure activ­i­ties that seem to have the most pos­i­tive effects?

YS: For our 2001 study we eval­u­at­ed the effect of 13 activ­i­ties, com­bin­ing intel­lec­tu­al, phys­i­cal, and social ele­ments. Some of the activ­i­ties with the most effect were read­ing, vis­it­ing friends or rel­a­tives, going to movies or restau­rants, and walk­ing for plea­sure or going on an excur­sion. As you can see, a vari­ety. We saw that the group with high lev­el of leisure activ­i­ties pre­sent­ed 38% less risk (con­trol­ling for oth­er fac­tors) of devel­op­ing Alzheimer’s symp­toms. And that, for each addi­tion­al type of activ­i­ty, the risk got reduced by 8%. There is an addi­tion­al ele­ment that we are start­ing to see more clear­ly. Phys­i­cal exer­cise, by itself, also has a very ben­e­fi­cial impact on cog­ni­tion. Only a few months ago researchers were able to show for the first time how phys­i­cal activ­i­ty pro­motes neu­ro­ge­n­e­sis in the human brain. So, we need both men­tal and phys­i­cal exer­cise. The not-so-good news is that, as of today, there no clear recipe for suc­cess. More research is need­ed before we pre­pare a sys­tem­at­ic set of inter­ven­tions that can help max­i­mize our protection.

AF: We typ­i­cal­ly empha­size the impor­tance of a good nutri­tion, phys­i­cal exer­cise, stress man­age­ment and men­tal exer­cise that presents nov­el­ty, vari­ety and chal­lenge. What do you think of the rel­a­tive­ly recent appear­ance of so many com­put­er-based cog­ni­tive train­ing pro­grams, some more sci­ence-based than others?

YS: Those ele­ments you men­tion make sense. The prob­lem is that, at least from the point of view of Alzheimer’s, we can­not be much more spe­cif­ic. We don’t know if learn­ing a new lan­guage is more ben­e­fi­cial than learn­ing a new musi­cal instru­ment or using a com­put­er-based pro­gram. A few of the cog­ni­tive train­ing com­put­er pro­grams we have seen, like the one you dis­cussed with Prof. Daniel Gopher to train the men­tal abil­i­ties of pilots, seem to have clear effects on cog­ni­tion, gen­er­al­iz­ing beyond the train­ing itself. But, for the most part, it is too ear­ly to tell the long-term effects. We need bet­ter designed clin­i­cal tri­als with clear con­trols. Right now, the most we can say is that those who lead men­tal­ly stim­u­lat­ing lives, through edu­ca­tion, occu­pa­tion and leisure activ­i­ties seem to have the least risk of devel­op­ing Alzheimer’s Disease.

Research inter­ests

AF: Tell us know a bit more about your cur­rent research

YS: We are study­ing a num­ber of relat­ed areas, apply­ing neu­roimag­ing tech­niques to under­stand how exact­ly all these Cog­ni­tive Reserve con­cepts are imple­ment­ed in the brain.

One, we want to under­stand indi­vid­ual dif­fer­ences in how peo­ple approach tasks. We want to mea­sure their effi­cien­cy and capac­i­ty the brain net­works that medi­ate tasks per­for­mance with the idea that those with greater effi­cien­cy and capac­i­ty might cope bet­ter with age-relat­ed prob­lems. For exam­ple, we can all under­stand that a com­pet­i­tive swim­mer is going to swim bet­ter than I would even if he has some weights in his legs, but we haven’t yet iden­ti­fied what exact­ly is the equiv­a­lent in the brain.

Sec­ond, we want to under­stand how old peo­ple com­pen­sate for the areas of decline. For exam­ple, do they begin to use new brain areas when the ones that are typ­i­cal­ly used start to fail.

Third, whether the Cog­ni­tive Reserve presents ben­e­fits beyond the pre­ven­tion of Alzheimer’s symp­toms. Does hav­ing a high­er reserve result in bet­ter atten­tion, bet­ter exec­u­tive func­tions, more suc­cess­ful aging overall?

AF: All very impor­tant top­ics. Thank you for your time, and please keep us informed.

YS: My plea­sure. Thank you for your great edu­ca­tion­al initiative.

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Sci­en­tif­ic references

Stern Y. Cog­ni­tive reserve and Alzheimer dis­ease. Alzheimer Dis Assoc Dis­ord. 2006, 20:112–117.

Scarmeas N, Albert SM, Man­ly J, Stern Y. Edu­ca­tion and rates of cog­ni­tive decline in inci­dent Alzheimer’s dis­ease. Jour­nal of Neu­rol­o­gy, Neu­ro­surgery, and Psy­chi­a­try, 2006;77:308–316.

Scarmeas N, Stern Y. Cog­ni­tive reserve and lifestyle. J Clin Exp Neu­ropsy­chol 2003;5:625–633.

Stern Y, Zarahn E, Hilton HJ, Fly­nn J, DeLa Paz R, Rak­itin B. Explor­ing the neur­al basis of cog­ni­tive reserve. J Clin Exp Neu­ropsy­chol 2003;5:691–701.