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Cognitive Reserve and Lifestyle

Update: we now have an in-depth inter­view with Yaakov Stern, lead­ing advo­cate of the cog­ni­tive reserve the­ory, and one of the authors of the paper we review below: click on Build Your Cog­ni­tive Reserve-Yaakov Stern. 

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In honor of the Week of Sci­ence pre­sented at Just Sci­ence from Mon­day, Feb­ru­ary 5, through Sun­day, Feb­ru­ary 11, we will be writ­ing about “just sci­ence” this week. We thought we would take this time to dis­cuss more deeply some of the key sci­en­tific pub­li­ca­tions in brain fitness.

Today, we will high­light the key points in an excel­lent review of cog­ni­tive reserve: Scarmeas, Niko­laos and Stern, Yaakov. Cog­ni­tive reserve and lifestyle. Jour­nal of Clin­i­cal and Exper­i­men­tal Neu­ropsy­chol­ogy. 2003;25:625–33.

What is Cog­ni­tive Reserve?
The con­cept of a cog­ni­tive reserve has been around since 1998 when a post mortem analy­sis of 137 peo­ple with Alzheimer’s Dis­ease showed that the patients exhib­ited fewer clin­i­cal symp­toms than their actual pathol­ogy sug­gested. (Katz­man et al. 1988) They 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 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.

Despite many stud­ies that demon­strate an asso­ci­a­tion between higher par­tic­i­pa­tion in more intel­lec­tual, social and phys­i­cal activ­i­ties and more reserve, most of these stud­ies were not done over a long enough time period to rule out whether the stim­u­lat­ing activ­i­ties were pro­mot­ing higher cog­ni­tive per­for­mance or higher per­form­ers were more likely to engage in stim­u­lat­ing activ­i­ties. The lon­gi­tu­di­nal stud­ies show a mutu­ally rein­forc­ing cycle between an ini­tially high intel­lec­tual func­tion­ing per­son, an engaged lifestyle, and more cog­ni­tive reserve, but also a main­te­nance of intel­lec­tual per­for­mance. (Arbuckle et al. 1992, Gold et al. 1995, Hultsch et al 1999, Schaie 1984, Schaie 1996, Schooler and Mulatu 2001)

In one study of 1772 non­de­mented indi­vid­u­als over seven years that con­trolled for fac­tors like eth­nic group, edu­ca­tion, and occu­pa­tion, par­tic­i­pants with high leisure activ­ity had 38% less risk of devel­op­ing demen­tia, and that risk was reduced by approx­i­mately 12% for each addi­tional leisure activ­ity adopted. (Scarmeas, Levy, et al. 2001) Later stud­ies, includ­ing imag­ing stud­ies of cere­bral blood flow, con­tinue to build up data show­ing fre­quent par­tic­i­pa­tion in cog­ni­tively stim­u­lat­ing activ­i­ties reduces risk for Alzheimer’s and slows the rate of cog­ni­tive decline. Inter­est­ingly, phys­i­cal, social, and intel­lec­tual activ­i­ties all help, although intel­lec­tual activ­i­ties were asso­ci­ated with the low­est risk of inci­dent demen­tia. Fur­ther­more, it has been shown that peo­ple with high cog­ni­tive reserve decline more rapidly, sup­port­ing the idea that the pathol­ogy is more advanced by the time it is clin­i­cally appar­ent. (Stern, Tang, et al. 1995)

Causal­ity

The asso­ci­a­tion between engaged lifestyle and demen­tia risk could be either medi­ated or con­founded by abil­i­ties like IQ or edu­ca­tion. If this is the case then it could be that either IQ or edu­ca­tion rep­re­sent the true causal links with demen­tia or that sub­jects with higher IQ or edu­ca­tion tend to adopt lifestyles which them­selves causally reduce the risk of demen­tia (such as exer­cise, diet, etc.). Nev­er­the­less, in stud­ies where edu­ca­tion and occu­pa­tion (Scarmeas et al. 2001) or edu­ca­tion and IQ (Scarmeas et al. 2003) were con­trolled for, the asso­ci­a­tion between leisure activ­i­ties and demen­tia risk was still there.

Other pos­si­bil­i­ties are that high func­tion­ing and engaged lifestyle are results of an innate capac­ity. Or per­haps bor­der­line demen­tia patients are less active as a result of the pathol­ogy. Or per­haps the con­nec­tion has yet to be found.

How Does it Work?
If it is a causal rela­tion­ship, there are four pos­si­ble expla­na­tions of how it might work:

  1. Par­tic­i­pa­tion in stim­u­lat­ing activ­i­ties spurs neu­ronal growth and a larger num­ber of neu­rons to com­pen­sate for the pathology
  2. High activ­ity peo­ple use the same num­ber of neural net­works more efficiently
  3. High activ­ity peo­ple use alter­nate neural net­works more effi­ciently to com­pen­sate for the pathology
  4. The fac­tors that affect cog­ni­tive reserve dis­rupt the devel­op­ment of the dis­ease pathol­ogy by decreas­ing neurodegeneration

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Update: we now have an in-depth inter­view with Yaakov Stern, lead­ing advo­cate of the cog­ni­tive reserve the­ory, and one of the authors of the paper we review below: click on Build Your Cog­ni­tive Reserve-Yaakov Stern.  

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Fur­ther Reading

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12 Responses

  1. […] Yes­ter­day we talked about Cog­ni­tive Reserve and Lifestyle, a paper and research area that helps build the case for men­tal stimulation/ brain exer­cise if we care about long-term healthy aging. […]

  2. […] Yes­ter­day we talked about Cog­ni­tive Reserve and Lifestyle, a paper and research area that helps build the case for men­tal stimulation/ brain exer­cise if we care about long-term healthy aging. […]

  3. […] Cog­ni­tive Neu­ro­science­Brain Fit­ness Glos­saryCog­ni­tive Reserve and Lifestylea href=“http://www.sharpbrains.com/blog/2007/02/11/heart-rate-variability-as-an-index-of-regulated-emotional-responding/”>Heart Rate Vari­abil­ity as an Index of Reg­u­lated Emo­tional Respond­ingNeu­ro­science Inter­view Series: on learn­ing and “brain gyms” […]

  4. […] Alvaro Fer­nan­dez presents Cog­ni­tive Reserve and Lifestyle posted at Sharp­Brains: Your Win­dow into the Brain Fit­ness Rev­o­lu­tion, say­ing, “Brief review of key papers on the Cog­ni­tive Reserve for healthy aging.” […]

  5. […] Car­o­line sum­ma­rizes the research behind Cog­ni­tive Reserve and Lifestyle that indi­cates how impor­tant men­tal stim­u­la­tion is for healthy brain aging. […]

  6. […] Alvaro also sent an arti­cle with his sug­ges­tion that learn­ing pro­tects against cog­ni­tive decline includ­ing demen­tia. Based on my read­ing of his sum­mary, I pro­pose that it is not just learn­ing (the intel­lec­tual stim­u­la­tion), but encom­passes to “high leisure activ­i­ties”, which I inter­pret as hav­ing a lot of fun and cre­ativ­ity in your life. Most geniuses are highly cre­ative peo­ple and some­times they can be a bit quirky, but they all immerse them­selves in intensely plea­sur­able activ­i­ties that for us look like “physics” or “writ­ing music” but for the geniuses are pure joy. […]

  7. […] 6– If we want to max­i­mize our chances of healthy aging, we should focus on 4 main “brain health” pil­lars: men­tal stim­u­la­tion, phys­i­cal exer­cise, stress management and a bal­anced diet. And the ear­lier the bet­ter to build a Cog­ni­tive Reserve. More info at The Dana Guide to Brain Health book review. […]

  8. […] We have seen a num­ber of stud­ies on why and how speak­ing more than one lan­guage may help build a Cog­ni­tive Reserve that pro­tects us against cog­ni­tive decline. This arti­cle does a good job at explain­ing what may be going on (bold added by me): […]

  9. […] Alvaro Fer­nan­dez presents Cog­ni­tive Reserve and Lifestyle posted at Sharp­Brains: Your Win­dow into the Brain Fit­ness Rev­o­lu­tion, say­ing, “Why change can lit­er­ally be good for your brain” […]

  10. Allene Wright says:

    I have just been intro­duced to the the­ory of cog­ni­tive reserve by a psy­chi­a­trist treat­ing a friend. I need to know as much as I can about the the­ory and am delighted in this website.

  11. Allene, glad to hear :-)

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