Study finds promise in smell training to harness neuroplasticity and improve brain health in older adults

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An impaired sense of smell can sig­nal cog­ni­tive decline, but ‘smell train­ing’ could help (The Conversation):

“As we age, we often have prob­lems with our abil­i­ty to smell (called olfac­to­ry dys­func­tion). Old­er peo­ple might not be able to iden­ti­fy an odour or dif­fer­en­ti­ate one odour from anoth­er. In some cas­es they might not be able to detect an odour at all.

Odour iden­ti­fi­ca­tion dif­fi­cul­ties are com­mon in peo­ple with neu­rode­gen­er­a­tive dis­eases, includ­ing Alzheimer’s dis­ease … But there is emerg­ing evi­dence that olfac­to­ry or “smell train­ing” can improve abil­i­ty to smell.

Neu­ro­plas­tic­i­ty, our brains’ abil­i­ty to change con­tin­u­ous­ly in response to expe­ri­ence, may be key to how smell train­ing works.

Neu­ro­plas­tic­i­ty involves the gen­er­a­tion of new con­nec­tions and/or the strength­en­ing of exist­ing con­nec­tions between neu­rons (brain cells), which in turn may lead to changes in think­ing skills or behav­iour. We can see evi­dence of neu­ro­plas­tic­i­ty when we prac­tise a skill such as play­ing an instru­ment or learn­ing a new language.

The olfac­to­ry net­work is con­sid­ered par­tic­u­lar­ly neu­ro­plas­tic. Neu­ro­plas­tic­i­ty may there­fore under­lie the pos­i­tive results from smell train­ing, both in terms of improv­ing olfac­to­ry abil­i­ty and boost­ing capac­i­ty for oth­er cog­ni­tive tasks … using the con­sid­er­able neu­ro­plas­tic­i­ty of the olfac­to­ry net­work and evi­dence-based cog­ni­tive train­ing tech­niques, both olfac­to­ry and cog­ni­tive deficits may be tar­get­ed, par­tic­u­lar­ly in old­er adults at risk of demen­tia. It seems pos­si­ble we could train our brains through our noses.”

The Study

Effects of olfac­to­ry train­ing: a meta-analy­sis. (Rhi­nol­o­gy Journal)

  • Abstract: The neur­al plas­tic­i­ty of the olfac­to­ry sys­tem offers pos­si­bil­i­ties of treat­ment in terms of stim­u­la­tion of the sense of smell, and dif­fer­ent stud­ies have sug­gest­ed effec­tive­ness of smell train­ing, i.e., dai­ly expo­si­tion to cer­tain odors. To obtain reli­able and pre­cise esti­mates of over­all treat­ment ben­e­fit on the olfac­to­ry func­tion, we meta-ana­lyzed the effects of smell train­ing report­ed in 13 pre­vi­ous stud­ies. We ana­lyzed the smell train­ing effec­tive­ness across three dif­fer­ent olfac­to­ry abil­i­ties, smell iden­ti­fi­ca­tion, dis­crim­i­na­tion and thresh­old for odor detec­tion. We found a sig­nif­i­cant, pos­i­tive effect of olfac­to­ry train­ing for all olfac­to­ry abil­i­ties, with large effects of train­ing on iden­ti­fi­ca­tion, dis­crim­i­na­tion and TDI-score and small-to-mod­er­ate effect in the case of thresh­old for odor detec­tion. Inter­est­ing­ly, the pat­tern of results dif­fered across Snif­fin Sticks sub­tests depend­ing on the ori­gin of par­tic­i­pants smell dis­or­der, and the smell train­ing dura­tion influ­enced its effec­tive­ness in the case of iden­ti­fi­ca­tion and the TDI score. Although the exact mech­a­nism of olfac­to­ry recov­ery fol­low­ing the smell train­ing still requires fur­ther inves­ti­ga­tion, our meta-analy­sis showed that such train­ing should be con­sid­ered an addi­tion or alter­na­tive to exist­ing smell treat­ment methods.

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