The more hours you sit per day, the smaller your medial temporal lobe (MTL) seems to become, brain scans show

—– In the study, both (A) Total medi­al tem­po­ral lobe (MTL) and (B) parahip­pocam­pal thick­ness cor­re­lat­ed inverse­ly with hours of sitting/day, con­trol­ling for age. Ref­er­ence: Sid­darth P et al (2018), Seden­tary behav­ior asso­ci­at­ed with reduced medi­al tem­po­ral lobe thick­ness in mid­dle-aged and old­er adults. PLOS ONE 13(4): e0195549.

Sit­ting is bad for your brain — not just your metab­o­lism or heart (UCLA release):

“UCLA researchers recruit­ed 35 peo­ple ages 45 to 75 and asked about their phys­i­cal activ­i­ty lev­els and the aver­age num­ber of hours per day they spent sit­ting over the pre­vi­ous week. Each per­son had a high-res­o­lu­tion MRI scan, which pro­vides a detailed look at the medi­al tem­po­ral lobe, or MTL, a brain region involved in the for­ma­tion of new memories.

The researchers found that seden­tary behav­ior is a sig­nif­i­cant pre­dic­tor of thin­ning of the MTL and that phys­i­cal activ­i­ty, even at high lev­els, is insuf­fi­cient to off­set the harm­ful effects of sit­ting for extend­ed periods…The researchers next hope to fol­low a group of peo­ple for a longer dura­tion to deter­mine if sit­ting caus­es the thin­ning and what role gen­der, race, and weight might play in brain health relat­ed to sitting.

MTL thin­ning can be a pre­cur­sor to cog­ni­tive decline and demen­tia in mid­dle-aged and old­er adults. Reduc­ing seden­tary behav­ior may be a pos­si­ble tar­get for inter­ven­tions designed to improve brain health in peo­ple at risk for Alzheimer’s dis­ease, researchers said.”

The Study:

Seden­tary behav­ior asso­ci­at­ed with reduced medi­al tem­po­ral lobe thick­ness in mid­dle-aged and old­er adults (PLOS One). From the abstract:

• (Back­ground) Atro­phy of the medi­al tem­po­ral lobe (MTL) occurs with aging, result­ing in impaired episod­ic mem­o­ry. Aer­o­bic fit­ness is pos­i­tive­ly cor­re­lat­ed with total hip­pocam­pal vol­ume, a heav­i­ly stud­ied mem­o­ry-crit­i­cal region with­in the MTL. How­ev­er, research on asso­ci­a­tions between seden­tary behav­ior and MTL sub­re­gion integri­ty is lim­it­ed. Here we explore asso­ci­a­tions between thick­ness of the MTL and its sub­re­gions, phys­i­cal activ­i­ty, and seden­tary behavior.
• (Meth­ods) We assessed 35 non-dement­ed mid­dle-aged and old­er adults (25 women, 10 men; 45–75 years) using the Inter­na­tion­al Phys­i­cal Activ­i­ty Ques­tion­naire for old­er adults, which quan­ti­fies phys­i­cal activ­i­ty lev­els in MET-equiv­a­lent units and asks about the aver­age num­ber of hours spent sit­ting per day. All par­tic­i­pants had high res­o­lu­tion MRI scans per­formed on a Siemens Alle­gra 3T MRI scan­ner, which allows for detailed inves­ti­ga­tion of the MTL.
• (Results) Con­trol­ling for age, total MTL thick­ness cor­re­lat­ed inverse­ly with hours of sitting/day (r = ‑0.37, p = 0.03). In MTL sub­re­gion analy­sis, parahip­pocam­pal (r = ‑0.45, p = 0.007), entorhi­nal (r = ‑0.33, p = 0.05) cor­ti­cal and subicu­lum (r = ‑0.36, p = .04) thick­ness­es cor­re­lat­ed inverse­ly with hours of sitting/day. No sig­nif­i­cant cor­re­la­tions were observed between phys­i­cal activ­i­ty lev­els and MTL thick­ness. Though pre­lim­i­nary, our results sug­gest that more seden­tary non-dement­ed indi­vid­u­als have less MTL thick­ness. Future stud­ies should include lon­gi­tu­di­nal analy­ses and explore mech­a­nisms, as well as the effi­ca­cy of decreas­ing seden­tary behav­iors to reverse this association.

The Study in Context:

• Can you grow your hip­pocam­pus? Yes. Here’s how, and why it matters
• Study: High tele­vi­sion view­ing and low phys­i­cal activ­i­ty can sig­nif­i­cant­ly wors­en long-term cog­ni­tive function
• How learn­ing changes your brain
• Solv­ing the Brain Fit­ness Puz­zle Is the Key to Self-Empow­ered Aging