1/10/2015 BrainsSweepThemselvesCleanOfToxinsDuringSleep:ShotsHealthNews:NPR

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ROBERTSIEGEL,HOST:

Thequestionofwhypeopleandanimalsneedsleephasbotheredscientistsfordecades.Andnow,researchersthinkthatthey'vefoundatleastpartoftheanswer.NPR'sJonHamiltonreportsonastudythatshowsthatduringsleep,thebrainflushesouttoxins,includingasubstancelinkedtoAlzheimer'sdisease.

JONHAMIILTON,BYLINE:Fromanevolutionarypointofview,sleepseemslikeabadidea.Afterall,whenyou'resnoozing,it'seasyforanothercreaturetoremoveyoufromthegenepool.That'sespeciallytrueifyou'reasmallrodent,saystheUniversityofRochester'sMaikenNedergaard.

DR.MAIKENNEDERGAARD:Foraanimallikeamouseorrat,it'sverydangeroustosleepbecauseit'smuchmorevulnerableforcatsthatwouldcomeandeatit.

JONHAMILTON,BYLINE:Sosleepmusthavesomereallyimportantsurvivalfunction.Tofindoutwhatthatmightbe,Nedergaardledateamthatstudiedthebrainsofsleepingmice.Andthescientistsnoticedthatduringsleep,somethingoddwashappeningtothesystemthatcirculatescerebrospinalfluidthroughthebrainandnervoussystem.

1/10/2015 BrainsSweepThemselvesCleanOfToxinsDuringSleep:ShotsHealthNews:NPR

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NEDERGAARD:Itwaspumpingfluidintothebrainandremovingfluidfromthebraininaveryrapidpace.

HAMILTON:Nedergaardsaystheteamrealizedthiswaspossibleinpartbecausewhenmicewenttosleep,theirbraincellsactuallyshrank,soitwaseasierforfluidtocirculate.Whenananimalwokeup,shesays,thebraincellsenlargedagainandtheflowbetweencellsslowedtoatrickle.

NEDERGAARD:It'salmostlikeopeningandclosingafaucet.It'sthatdramatic.

HAMILTON:Nedergaardandherteamhadpreviouslyshownthatthefluidwascarryingawaywasteproductsthatbuildupinthespacesbetweencells.

NEDERGAARD:It'slikeadishwasher.It'sfloatingbyallthecells,whicharethedishes,andwashingthem.

HAMILTON:That'simportantbecausewhat'sgettingwashedawayduringsleeparewasteproteinsthataretoxictobraincells.Nedergaardsaysthisprocesscouldexplainwhywedon'tthinkclearlyafterasleeplessnightandwhyaprolongedlackofsleepcanactuallykillananimaloraperson.Butwhydoesn'tthebraindothissortofhousekeepingallthetime?Nedergaardthinksit'sbecausecleaningtakesalotofenergy.

NEDERGAARD:It'sprobablynotpossibleforthebraintobothcleanitselfandatthesametimebeingawareofthesurroundingsandtalkandmoveandsoon.

HAMILTON:Andthatwouldexplainwhyanimalshaveevolvedtoneedsleep.Nedergaardsaysthecleaningprocesshasbeenobservedinratsandbaboonsbutnotyetinhumans.Evenso,itcouldofferanewwayofunderstandinghumanbraindiseases,includingAlzheimer's.That'sbecauseoneofthewasteproductsremovedfromthebrainduringsleepisbetaamyloid,thesubstancethatformsstickyplaquesassociatedwithAlzheimer's.Nedergaardsaysthat'sprobablynotacoincidence.

NEDERGAARD:Isn'titinterestingthatAlzheimerandallotherdiseasesassociated

1/10/2015 BrainsSweepThemselvesCleanOfToxinsDuringSleep:ShotsHealthNews:NPR

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withdementia,theyarelinkedtosleepdisorders.Sothepatientwouldsleeplessandlessandtheywouldnothavedeepsleep.

HAMILTON:ResearcherswhostudyAlzheimer'ssayNedergaard'sresearchcouldhelpexplainanumberofrecentfindingsrelatedtosleep.RandallBatemanofWashingtonUniversityinSt.LouiswaspartofateamthatstudiedhowsleepaffectslevelsofthatAlzheimer'sprotein,betaamyloid.

DR.RANDALLBATEMAN:Betaamyloidconcentrationscontinuetoincreasewhileapersonisawake.Andthenafterpeoplegotosleep,thatconcentrationofbetaamyloiddecreases.Thisreportprovidesabeautifulmechanismbywhichthismaybehappening.

HAMILTON:BatemansaysthereportalsooffersatantalizinghintofanewapproachtoAlzheimer'sprevention.

BATEMAN:ItdoesraisethepossibilitythatonemightbeabletoactuallycontrolsleepinawaytoimprovetheclearanceofbetaamyloidandhelppreventamyloidosisthatwethinkcanleadtoAlzheimer'sdisease.

HAMILTON:ThenewresearchappearsinthejournalScience.JonHamilton,NPRNews.

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