brain basics - understanding sleep

24/01/2015 BrainBasics:UnderstandingSleep:NationalInstituteofNeurologicalDisordersandStroke(NINDS)

http://www.ninds.nih.gov/disorders/brain_basics/understanding_sleep.htm 1/11

BrainBasics:UnderstandingSleep

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Doyoueverfeelsleepyor"zoneout"duringtheday?DoyoufindithardtowakeuponMondaymornings?Ifso,youarefamiliarwiththepowerfulneedforsleep.However,youmaynotrealizethatsleepisasessentialforyourwellbeingasfoodandwater.

Sleep:ADynamicActivityHowMuchSleepDoWeNeed?WhatDoesSleepDoForUs?DreamingandREMSleepSleepandCircadianRhythmsSleepandDiseaseSleepDisordersTheFutureTipsforaGoodNight'sSleep

Sleep:ADynamicActivity

Untilthe1950s,mostpeoplethoughtofsleepasapassive,dormantpartofourdailylives.Wenowknowthatourbrainsareveryactiveduringsleep.Moreover,sleepaffectsourdailyfunctioningandourphysicalandmentalhealthinmanywaysthatwearejustbeginningtounderstand.

Nervesignalingchemicalscalledneurotransmitterscontrolwhetherweareasleeporawakebyactingondifferentgroupsofnervecells,orneurons,inthebrain.Neuronsinthebrainstem,whichconnectsthebrainwiththespinalcord,produceneurotransmitterssuchasserotoninandnorepinephrinethatkeepsomepartsofthebrainactivewhileweareawake.Otherneuronsatthebaseofthebrainbeginsignalingwhenwefallasleep.Theseneuronsappearto"switchoff"thesignalsthatkeepusawake.Researchalsosuggeststhatachemicalcalledadenosinebuildsupinourbloodwhileweareawakeandcausesdrowsiness.Thischemicalgraduallybreaksdownwhilewesleep.

Duringsleep,weusuallypassthroughfivephasesofsleep:stages1,2,3,4,andREM(rapideyemovement)sleep.Thesestagesprogressinacyclefromstage1toREMsleep,thenthecyclestartsoveragainwithstage1(seefigure1).Wespendalmost50percentofourtotalsleeptimeinstage2sleep,about20percentinREMsleep,andtheremaining30percentintheotherstages.Infants,bycontrast,spendabouthalfoftheirsleeptimeinREMsleep.

Duringstage1,whichislightsleep,wedriftinandoutofsleepandcanbeawakenedeasily.Oureyesmoveveryslowlyandmuscleactivityslows.Peopleawakenedfromstage1sleepoftenrememberfragmentedvisualimages.Manyalsoexperiencesuddenmusclecontractionscalledhypnicmyoclonia,oftenprecededbyasensationofstartingtofall.Thesesuddenmovementsaresimilartothe"jump"wemakewhenstartled.Whenweenterstage2sleep,oureyemovementsstopandourbrainwaves(fluctuationsof

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electricalactivitythatcanbemeasuredbyelectrodes)becomeslower,withoccasionalburstsofrapidwavescalledsleepspindles.Instage3,extremelyslowbrainwavescalleddeltawavesbegintoappear,interspersedwithsmaller,fasterwaves.Bystage4,thebrainproducesdeltawavesalmostexclusively.Itisverydifficulttowakesomeoneduringstages3and4,whichtogetherarecalleddeepsleep.Thereisnoeyemovementormuscleactivity.Peopleawakenedduringdeepsleepdonotadjustimmediatelyandoftenfeelgroggyanddisorientedforseveralminutesaftertheywakeup.Somechildrenexperiencebedwetting,nightterrors,orsleepwalkingduringdeepsleep.

WhenweswitchintoREMsleep,ourbreathingbecomesmorerapid,irregular,andshallow,oureyesjerkrapidlyinvariousdirections,andourlimbmusclesbecometemporarilyparalyzed.Ourheartrateincreases,ourbloodpressurerises,andmalesdeveloppenileerections.WhenpeopleawakenduringREMsleep,theyoftendescribebizarreandillogicaltalesdreams.

ThefirstREMsleepperiodusuallyoccursabout70to90minutesafterwefallasleep.Acompletesleepcycletakes90to110minutesonaverage.ThefirstsleepcycleseachnightcontainrelativelyshortREMperiodsandlongperiodsofdeepsleep.Asthenightprogresses,REMsleepperiodsincreaseinlengthwhiledeepsleepdecreases.Bymorning,peoplespendnearlyalltheirsleeptimeinstages1,2,andREM.

Peopleawakenedaftersleepingmorethanafewminutesareusuallyunabletorecallthelastfewminutesbeforetheyfellasleep.Thissleeprelatedformofamnesiaisthereasonpeopleoftenforgettelephonecallsorconversationsthey'vehadinthemiddleofthenight.Italsoexplainswhyweoftendonotrememberouralarmsringinginthemorningifwegorightbacktosleepafterturningthemoff.

Sincesleepandwakefulnessareinfluencedbydifferentneurotransmittersignalsinthebrain,foodsandmedicinesthatchangethebalanceofthesesignalsaffectwhetherwefeelalertordrowsyandhowwellwesleep.Caffeinateddrinkssuchascoffeeanddrugssuchasdietpillsanddecongestantsstimulatesomepartsofthebrainandcancauseinsomnia,oraninabilitytosleep.ManyantidepressantssuppressREMsleep.HeavysmokersoftensleepverylightlyandhavereducedamountsofREMsleep.Theyalsotendtowakeupafter3or4hoursofsleepduetonicotinewithdrawal.Manypeoplewhosufferfrominsomniatrytosolvetheproblemwithalcoholthesocallednightcap.Whilealcoholdoeshelppeoplefallintolightsleep,italsorobsthemofREMandthedeeper,morerestorativestagesofsleep.Instead,itkeepstheminthelighterstagesofsleep,fromwhichtheycanbeawakenedeasily.

PeoplelosesomeoftheabilitytoregulatetheirbodytemperatureduringREM,soabnormallyhotorcoldtemperaturesintheenvironmentcandisruptthisstageofsleep.IfourREMsleepisdisruptedonenight,ourbodiesdon'tfollowthenormalsleepcycleprogressionthenexttimewedozeoff.Instead,weoftenslipdirectlyintoREMsleepandgothroughextendedperiodsofREMuntilwe"catchup"onthisstageofsleep.

Peoplewhoareunderanesthesiaorinacomaareoftensaidtobeasleep.However,peopleintheseconditionscannotbeawakenedanddonotproducethecomplex,activebrainwavepatternsseeninnormalsleep.Instead,theirbrainwavesareveryslowandweak,sometimesallbutundetectable.

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HowMuchSleepDoWeNeed?



Theamountofsleepeachpersonneedsdependsonmanyfactors,includingage.Infantsgenerallyrequireabout16hoursaday,whileteenagersneedabout9hoursonaverage.Formostadults,7to8hoursanightappearstobethebestamountofsleep.Womeninthefirst3monthsofpregnancyoftenneedseveralmorehoursofsleepthanusual.Theamountofsleepapersonneedsalsoincreasesifheorshehasbeendeprivedofsleepinpreviousdays.Gettingtoolittlesleepcreatesa"sleepdebt,"whichismuchlikebeingoverdrawnatabank.Eventually,yourbodywilldemandthatthedebtberepaid.Wedon'tseemtoadapttogettinglesssleepthanweneedwhilewemaygetusedtoasleepdeprivingschedule,ourjudgment,reactiontime,andotherfunctionsarestillimpaired.

Peopletendtosleepmorelightlyandforshortertimespansastheygetolder,althoughtheygenerallyneedaboutthesameamountofsleepastheyneededinearlyadulthood.Abouthalfofallpeopleover65havefrequentsleepingproblems,suchasinsomnia,anddeepsleepstagesinmanyelderlypeopleoftenbecomeveryshortorstopcompletely.Thischangemaybeanormalpartofaging,oritmayresultfrommedicalproblemsthatarecommoninelderlypeopleandfromthemedicationsandothertreatmentsforthoseproblems.

Expertssaythatifyoufeeldrowsyduringtheday,evenduringboringactivities,youhaven'thadenoughsleep.Ifyouroutinelyfallasleepwithin5minutesoflyingdown,youprobablyhaveseveresleepdeprivation,possiblyevenasleepdisorder.Microsleeps,orverybriefepisodesofsleepinanotherwiseawakeperson,areanothermarkofsleepdeprivation.Inmanycases,peoplearenotawarethattheyareexperiencingmicrosleeps.Thewidespreadpracticeof"burningthecandleatbothends"inwesternindustrializedsocietieshascreatedsomuchsleepdeprivationthatwhatisreallyabnormalsleepinessisnowalmostthenorm.

Manystudiesmakeitclearthatsleepdeprivationisdangerous.Sleepdeprivedpeoplewhoaretestedbyusingadrivingsimulatororbyperformingahandeyecoordinationtaskperformasbadlyasorworsethanthosewhoareintoxicated.Sleepdeprivationalsomagnifiesalcohol'seffectsonthebody,soafatiguedpersonwhodrinkswillbecomemuchmoreimpairedthansomeonewhoiswellrested.Driverfatigueisresponsibleforanestimated100,000motorvehicleaccidentsand1500deathseachyear,accordingtotheNationalHighwayTrafficSafetyAdministration.Sincedrowsinessisthebrain'slaststepbeforefallingasleep,drivingwhiledrowsycanandoftendoesleadtodisaster.Caffeineandotherstimulantscannotovercometheeffectsofseveresleepdeprivation.TheNationalSleepFoundationsaysthatifyouhavetroublekeepingyoureyesfocused,ifyoucan'tstopyawning,orifyoucan'trememberdrivingthelastfewmiles,youareprobablytoodrowsytodrivesafely.

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WhatDoesSleepDoForUs?

Althoughscientistsarestilltryingtolearnexactlywhypeopleneedsleep,animalstudiesshowthatsleepisnecessaryforsurvival.Forexample,whileratsnormallylivefortwotothreeyears,thosedeprivedofREMsleepsurviveonlyabout5weeksonaverage,andratsdeprivedofallsleepstagesliveonlyabout3weeks.Sleepdeprivedratsalsodevelopabnormallylowbodytemperaturesandsoresontheirtailandpaws.Thesoresmaydevelopbecausetherats'immunesystemsbecomeimpaired.Somestudiessuggestthatsleepdeprivationaffectstheimmunesystemindetrimentalways.

Sleepappearsnecessaryforournervoussystemstoworkproperly.Toolittlesleepleavesusdrowsyandunabletoconcentratethenextday.Italsoleadstoimpairedmemoryand



physicalperformanceandreducedabilitytocarryoutmathcalculations.Ifsleepdeprivationcontinues,hallucinationsandmoodswingsmaydevelop.Someexpertsbelievesleepgivesneuronsusedwhileweareawakeachancetoshutdownandrepairthemselves.Withoutsleep,neuronsmaybecomesodepletedinenergyorsopollutedwithbyproductsofnormalcellularactivitiesthattheybegintomalfunction.Sleepalsomaygivethebrainachancetoexerciseimportantneuronalconnectionsthatmightotherwisedeterioratefromlackofactivity.

Deepsleepcoincideswiththereleaseofgrowthhormoneinchildrenandyoungadults.Manyofthebody'scellsalsoshowincreasedproductionandreducedbreakdownofproteinsduringdeepsleep.Sinceproteinsarethebuildingblocksneededforcellgrowthandforrepairofdamagefromfactorslikestressandultravioletrays,deepsleepmaytrulybe"beautysleep."Activityinpartsofthebrainthatcontrolemotions,decisionmakingprocesses,andsocialinteractionsisdrasticallyreducedduringdeepsleep,suggestingthatthistypeofsleepmayhelppeoplemaintainoptimalemotionalandsocialfunctioningwhiletheyareawake.Astudyinratsalsoshowedthatcertainnervesignalingpatternswhichtheratsgeneratedduringthedaywererepeatedduringdeepsleep.Thispatternrepetitionmayhelpencodememoriesandimprovelearning.

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DreamingandREMSleep

Wetypicallyspendmorethan2hourseachnightdreaming.Scientistsdonotknowmuchabouthoworwhywedream.SigmundFreud,whogreatlyinfluencedthefieldofpsychology,believeddreamingwasa"safetyvalve"forunconsciousdesires.Onlyafter1953,whenresearchersfirstdescribedREMinsleepinginfants,didscientistsbegintocarefullystudysleepanddreaming.Theysoonrealizedthatthestrange,illogicalexperienceswecalldreamsalmostalwaysoccurduringREMsleep.WhilemostmammalsandbirdsshowsignsofREMsleep,reptilesandothercoldbloodedanimalsdonot.

REMsleepbeginswithsignalsfromanareaatthebaseofthebraincalledthepons(seefigure2).Thesesignalstraveltoabrainregioncalledthethalamus,whichrelaysthemtothecerebralcortextheouterlayerofthebrainthatisresponsibleforlearning,thinking,andorganizinginformation.Theponsalsosendssignalsthatshutoffneuronsinthespinalcord,causingtemporaryparalysisofthelimbmuscles.Ifsomethinginterfereswiththisparalysis,peoplewillbegintophysically"actout"theirdreamsarare,dangerousproblemcalledREMsleepbehaviordisorder.Apersondreamingaboutaballgame,forexample,mayrunheadlongintofurnitureorblindlystrikesomeonesleepingnearbywhiletryingtocatchaballinthedream.

REMsleepstimulatesthebrainregionsusedinlearning.Thismaybeimportantfornormalbraindevelopmentduringinfancy,whichwouldexplainwhyinfantsspendmuchmoretimeinREMsleepthanadults(seeSleep:ADynamicActivity).Likedeepsleep,REMsleepisassociatedwithincreasedproductionofproteins.OnestudyfoundthatREMsleepaffectslearningofcertainmentalskills.PeopletaughtaskillandthendeprivedofnonREMsleepcouldrecallwhattheyhadlearnedaftersleeping,whilepeopledeprivedofREMsleepcouldnot.

Somescientistsbelievedreamsarethecortex'sattempttofindmeaningintherandomsignalsthatitreceivesduringREMsleep.Thecortexisthepartofthebrainthatinterpretsandorganizesinformationfromtheenvironmentduringconsciousness.Itmaybethat,givenrandomsignalsfromtheponsduringREMsleep,thecortextriestointerpretthese

http://www.ninds.nih.gov/img/sleep-2.gif



signalsaswell,creatinga"story"outoffragmentedbrainactivity.

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SleepandCircadianRhythms

Circadianrhythmsareregularchangesinmentalandphysicalcharacteristicsthatoccurinthecourseofaday(circadianisLatinfor"aroundaday").Mostcircadianrhythmsarecontrolledbythebody'sbiological"clock."Thisclock,calledthesuprachiasmaticnucleusorSCN(seefigure2),isactuallyapairofpinheadsizedbrainstructuresthattogethercontainabout20,000neurons.TheSCNrestsinapartofthebraincalledthehypothalamus,justabovethepointwheretheopticnervescross.Lightthatreachesphotoreceptorsintheretina(atissueatthebackoftheeye)createssignalsthattravelalongtheopticnervetotheSCN.

SignalsfromtheSCNtraveltoseveralbrainregions,includingthepinealgland,whichrespondstolightinducedsignalsbyswitchingoffproductionofthehormonemelatonin.Thebody'slevelofmelatoninnormallyincreasesafterdarknessfalls,makingpeoplefeeldrowsy.TheSCNalsogovernsfunctionsthataresynchronizedwiththesleep/wakecycle,includingbodytemperature,hormonesecretion,urineproduction,andchangesinbloodpressure.

Bydeprivingpeopleoflightandotherexternaltimecues,scientistshavelearnedthatmostpeople'sbiologicalclocksworkona25hourcycleratherthana24hourone.ButbecausesunlightorotherbrightlightscanresettheSCN,ourbiologicalcyclesnormallyfollowthe24hourcycleofthesun,ratherthanourinnatecycle.Circadianrhythmscanbeaffectedtosomedegreebyalmostanykindofexternaltimecue,suchasthebeepingofyouralarmclock,theclatterofagarbagetruck,orthetimingofyourmeals.Scientistscallexternaltimecueszeitgebers(Germanfor"timegivers").

Whentravelerspassfromonetimezonetoanother,theysufferfromdisruptedcircadianrhythms,anuncomfortablefeelingknownasjetlag.Forinstance,ifyoutravelfromCaliforniatoNewYork,you"lose"3hoursaccordingtoyourbody'sclock.Youwillfeeltiredwhenthealarmringsat8a.m.thenextmorningbecause,accordingtoyourbody'sclock,itisstill5a.m.Itusuallytakesseveraldaysforyourbody'scyclestoadjusttothenewtime.

Toreducetheeffectsofjetlag,somedoctorstrytomanipulatethebiologicalclockwithatechniquecalledlighttherapy.Theyexposepeopletospeciallights,manytimesbrighterthanordinaryhouseholdlight,forseveralhoursnearthetimethesubjectswanttowakeup.Thishelpsthemresettheirbiologicalclocksandadjusttoanewtimezone.

Symptomsmuchlikejetlagarecommoninpeoplewhoworknightsorwhoperformshiftwork.Becausethesepeople'sworkschedulesareatoddswithpowerfulsleepregulatingcueslikesunlight,theyoftenbecomeuncontrollablydrowsyduringwork,andtheymaysufferinsomniaorotherproblemswhentheytrytosleep.Shiftworkershaveanincreasedriskofheartproblems,digestivedisturbances,andemotionalandmentalproblems,allofwhichmayberelatedtotheirsleepingproblems.Thenumberandseverityofworkplaceaccidentsalsotendtoincreaseduringthenightshift.MajorindustrialaccidentsattributedpartlytoerrorsmadebyfatiguednightshiftworkersincludetheExxonValdezoilspillandtheThreeMileIslandandChernobylnuclearpowerplantaccidents.Onestudyalsofoundthatmedicalinternsworkingonthenightshiftaretwiceaslikelyasotherstomisinterprethospitaltestrecords,whichcouldendangertheirpatients.Itmaybepossibletoreduceshiftrelatedfatiguebyusingbrightlightsintheworkplace,minimizingshiftchanges,and




takingschedulednaps.

Manypeoplewithtotalblindnessexperiencelifelongsleepingproblemsbecausetheirretinasareunabletodetectlight.Thesepeoplehaveakindofpermanentjetlagandperiodicinsomniabecausetheircircadianrhythmsfollowtheirinnatecycleratherthana24hourone.Dailysupplementsofmelatoninmayimprovenighttimesleepforsuchpatients.However,sincethehighdosesofmelatoninfoundinmostsupplementscanbuildupinthebody,longtermuseofthissubstancemaycreatenewproblems.Becausethepotentialsideeffectsofmelatoninsupplementsarestilllargelyunknown,mostexpertsdiscouragemelatoninusebythegeneralpublic.

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SleepandDisease

Sleepandsleeprelatedproblemsplayaroleinalargenumberofhumandisordersandaffectalmosteveryfieldofmedicine.Forexample,problemslikestrokeandasthmaattackstendtooccurmorefrequentlyduringthenightandearlymorning,perhapsduetochangesinhormones,heartrate,andothercharacteristicsassociatedwithsleep.Sleepalsoaffectssomekindsofepilepsyincomplexways.REMsleepseemstohelppreventseizuresthatbegininonepartofthebrainfromspreadingtootherbrainregions,whiledeepsleepmaypromotethespreadoftheseseizures.Sleepdeprivationalsotriggersseizuresinpeoplewithsometypesofepilepsy.

Neuronsthatcontrolsleepinteractcloselywiththeimmunesystem.Asanyonewhohashadthefluknows,infectiousdiseasestendtomakeusfeelsleepy.Thisprobablyhappensbecausecytokines,chemicalsourimmunesystemsproducewhilefightinganinfection,arepowerfulsleepinducingchemicals.Sleepmayhelpthebodyconserveenergyandotherresourcesthattheimmunesystemneedstomountanattack.

Sleepingproblemsoccurinalmostallpeoplewithmentaldisorders,includingthosewithdepressionandschizophrenia.Peoplewithdepression,forexample,oftenawakenintheearlyhoursofthemorningandfindthemselvesunabletogetbacktosleep.Theamountofsleepapersongetsalsostronglyinfluencesthesymptomsofmentaldisorders.Sleepdeprivationisaneffectivetherapyforpeoplewithcertaintypesofdepression,whileitcanactuallycausedepressioninotherpeople.Extremesleepdeprivationcanleadtoaseeminglypsychoticstateofparanoiaandhallucinationsinotherwisehealthypeople,anddisruptedsleepcantriggerepisodesofmania(agitationandhyperactivity)inpeoplewithmanicdepression.

Sleepingproblemsarecommoninmanyotherdisordersaswell,includingAlzheimer'sdisease,stroke,cancer,andheadinjury.Thesesleepingproblemsmayarisefromchangesinthebrainregionsandneurotransmittersthatcontrolsleep,orfromthedrugsusedtocontrolsymptomsofotherdisorders.Inpatientswhoarehospitalizedorwhoreceiveroundtheclockcare,treatmentschedulesorhospitalroutinesalsomaydisruptsleep.Theoldjokeaboutapatientbeingawakenedbyanursesohecouldtakeasleepingpillcontainsagrainoftruth.Oncesleepingproblemsdevelop,theycanaddtoaperson'simpairmentandcauseconfusion,frustration,ordepression.Patientswhoareunabletosleepalsonoticepainmoreandmayincreasetheirrequestsforpainmedication.Bettermanagementofsleepingproblemsinpeoplewhohaveotherdisorderscouldimprovethesepatients'healthandqualityoflife.

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SleepDisorders

Atleast40millionAmericanseachyearsufferfromchronic,longtermsleepdisorderseachyear,andanadditional20millionexperienceoccasionalsleepingproblems.Thesedisordersandtheresultingsleepdeprivationinterferewithwork,driving,andsocialactivities.Theyalsoaccountforanestimated$16billioninmedicalcostseachyear,whiletheindirectcostsduetolostproductivityandotherfactorsareprobablymuchgreater.Doctorshavedescribedmorethan70sleepdisorders,mostofwhichcanbemanagedeffectivelyoncetheyarecorrectlydiagnosed.Themostcommonsleepdisordersincludeinsomnia,sleepapnea,restlesslegssyndrome,andnarcolepsy.

InsomniaSleepApneaRestlessLegsSyndromeNarcolepsy

Insomnia

Almosteveryoneoccasionallysuffersfromshortterminsomnia.Thisproblemcanresultfromstress,jetlag,diet,ormanyotherfactors.Insomniaalmostalwaysaffectsjobperformanceandwellbeingthenextday.About60millionAmericansayearhaveinsomniafrequentlyorforextendedperiodsoftime,whichleadstoevenmoreserioussleepdeficits.Insomniatendstoincreasewithageandaffectsabout40percentofwomenand30percentofmen.Itisoftenthemajordisablingsymptomofanunderlyingmedicaldisorder.

Forshortterminsomnia,doctorsmayprescribesleepingpills.Mostsleepingpillsstopworkingafterseveralweeksofnightlyuse,however,andlongtermusecanactuallyinterferewithgoodsleep.Mildinsomniaoftencanbepreventedorcuredbypracticinggoodsleephabits(see"TipsforaGoodNight'sSleep").Formoreseriouscasesofinsomnia,researchersareexperimentingwithlighttherapyandotherwaystoaltercircadiancycles.

SleepApnea

Sleepapneaisadisorderofinterruptedbreathingduringsleep.Itusuallyoccursinassociationwithfatbuilduporlossofmuscletonewithaging.Thesechangesallowthewindpipetocollapseduringbreathingwhenmusclesrelaxduringsleep(seefigure3).Thisproblem,calledobstructivesleepapnea,isusuallyassociatedwithloudsnoring(thoughnoteveryonewhosnoreshasthisdisorder).Sleepapneaalsocanoccuriftheneuronsthatcontrolbreathingmalfunctionduringsleep.

Duringanepisodeofobstructiveapnea,theperson'sefforttoinhaleaircreatessuctionthatcollapsesthewindpipe.Thisblockstheairflowfor10secondstoaminutewhilethesleepingpersonstrugglestobreathe.Whentheperson'sbloodoxygenlevelfalls,thebrainrespondsbyawakeningthepersonenoughtotightentheupperairwaymusclesandopenthewindpipe.Thepersonmaysnortorgasp,thenresumesnoring.Thiscyclemayberepeatedhundredsoftimesanight.Thefrequentawakeningsthatsleepapneapatientsexperienceleavethemcontinuallysleepyandmayleadtopersonalitychangessuchasirritabilityordepression.Sleepapneaalsodeprivesthepersonofoxygen,whichcanleadtomorningheadaches,alossofinterestinsex,oradeclineinmentalfunctioning.Italsoislinkedtohighbloodpressure,irregularheartbeats,andanincreased




riskofheartattacksandstroke.Patientswithsevere,untreatedsleepapneaaretwotothreetimesmorelikelytohaveautomobileaccidentsthanthegeneralpopulation.Insomehighriskindividuals,sleepapneamayevenleadtosuddendeathfromrespiratoryarrestduringsleep.

Anestimated18millionAmericanshavesleepapnea.However,fewofthemhavehadtheproblemdiagnosed.Patientswiththetypicalfeaturesofsleepapnea,suchasloudsnoring,obesity,andexcessivedaytimesleepiness,shouldbereferredtoaspecializedsleepcenterthatcanperformatestcalledpolysomnography.Thistestrecordsthepatient'sbrainwaves,heartbeat,andbreathingduringanentirenight.Ifsleepapneaisdiagnosed,severaltreatmentsareavailable.Mildsleepapneafrequentlycanbeovercomethroughweightlossorbypreventingthepersonfromsleepingonhisorherback.Otherpeoplemayneedspecialdevicesorsurgerytocorrecttheobstruction.Peoplewithsleepapneashouldnevertakesedativesorsleepingpills,whichcanpreventthemfromawakeningenoughtobreathe.

RestlessLegsSyndrome

Restlesslegssyndrome(RLS),afamilialdisordercausingunpleasantcrawling,prickling,ortinglingsensationsinthelegsandfeetandanurgetomovethemforrelief,isemergingasoneofthemostcommonsleepdisorders,especiallyamongolderpeople.Thisdisorder,whichaffectsasmanyas12millionAmericans,leadstoconstantlegmovementduringthedayandinsomniaatnight.SevereRLSismostcommoninelderlypeople,thoughsymptomsmaydevelopatanyage.Insomecases,itmaybelinkedtootherconditionssuchasanemia,pregnancy,ordiabetes.

ManyRLSpatientsalsohaveadisorderknownasperiodiclimbmovementdisorderorPLMD,whichcausesrepetitivejerkingmovementsofthelimbs,especiallythelegs.Thesemovementsoccurevery20to40secondsandcauserepeatedawakeningandseverelyfragmentedsleep.Inonestudy,RLSandPLMDaccountedforathirdoftheinsomniaseeninpatientsolderthanage60.

RLSandPLMDoftencanberelievedbydrugsthataffecttheneurotransmitterdopamine,suggestingthatdopamineabnormalitiesunderliethesedisorders'symptoms.Learninghowthesedisordersoccurmayleadtobettertherapiesinthefuture.

Narcolepsy

Narcolepsyaffectsanestimated250,000Americans.Peoplewithnarcolepsyhavefrequent"sleepattacks"atvarioustimesoftheday,eveniftheyhavehadanormalamountofnighttimesleep.Theseattackslastfromseveralsecondstomorethan30minutes.Peoplewithnarcolepsyalsomayexperiencecataplexy(lossofmusclecontrolduringemotionalsituations),hallucinations,temporaryparalysiswhentheyawaken,anddisruptednighttimesleep.ThesesymptomsseemtobefeaturesofREMsleepthatappearduringwaking,whichsuggeststhatnarcolepsyisadisorderofsleepregulation.Thesymptomsofnarcolepsytypicallyappearduringadolescence,thoughitoftentakesyearstoobtainacorrectdiagnosis.Thedisorder(oratleastapredispositiontoit)isusuallyhereditary,butitoccasionallyislinkedtobraindamagefromaheadinjuryorneurologicaldisease.

Oncenarcolepsyisdiagnosed,stimulants,antidepressants,orotherdrugscanhelp



controlthesymptomsandpreventtheembarrassinganddangerouseffectsoffallingasleepatimpropertimes.Napsatcertaintimesofthedayalsomayreducetheexcessivedaytimesleepiness.

In1999,aresearchteamworkingwithcaninemodelsidentifiedagenethatcausesnarcolepsyabreakthroughthatbringsacureforthisdisablingconditionwithinreach.Thegene,hypocretinreceptor2,codesforaproteinthatallowsbraincellstoreceiveinstructionsfromothercells.Thedefectiveversionsofthegeneencodeproteinsthatcannotrecognizethesemessages,perhapscuttingthecellsofffrommessagesthatpromotewakefulness.Theresearchersknowthatthesamegeneexistsinhumans,andtheyarecurrentlysearchingfordefectiveversionsinpeoplewithnarcolepsy.

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TheFuture

Sleepresearchisexpandingandattractingmoreandmoreattentionfromscientists.Researchersnowknowthatsleepisanactiveanddynamicstatethatgreatlyinfluencesourwakinghours,andtheyrealizethatwemustunderstandsleeptofullyunderstandthebrain.Innovativetechniques,suchasbrainimaging,cannowhelpresearchersunderstandhowdifferentbrainregionsfunctionduringsleepandhowdifferentactivitiesanddisordersaffectsleep.Understandingthefactorsthataffectsleepinhealthanddiseasealsomayleadtorevolutionarynewtherapiesforsleepdisordersandtowaysofovercomingjetlagandtheproblemsassociatedwithshiftwork.Wecanexpecttheseandmanyotherbenefitsfromresearchthatwillallowustotrulyunderstandsleep'simpactonourlives.

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TipsforaGoodNight'sSleep:

Adaptedfrom"WhenYouCan'tSleep:TheABCsofZZZs,"bytheNationalSleepFoundation.

Setaschedule:

Gotobedatasettimeeachnightandgetupatthesametimeeachmorning.Disruptingthisschedulemayleadtoinsomnia."Sleepingin"onweekendsalsomakesithardertowakeupearlyonMondaymorningbecauseitresetsyoursleepcyclesforalaterawakening.

Exercise:

Trytoexercise20to30minutesaday.Dailyexerciseoftenhelpspeoplesleep,althoughaworkoutsoonbeforebedtimemayinterferewithsleep.Formaximumbenefit,trytogetyourexerciseabout5to6hoursbeforegoingtobed.

Avoidcaffeine,nicotine,andalcohol:

Avoiddrinksthatcontaincaffeine,whichactsasastimulantandkeepspeopleawake.Sourcesofcaffeineincludecoffee,chocolate,softdrinks,nonherbalteas,dietdrugs,andsomepainrelievers.Smokerstendtosleepverylightlyandoftenwakeupintheearlymorningduetonicotinewithdrawal.AlcoholrobspeopleofdeepsleepandREMsleepandkeepstheminthelighterstagesofsleep.



Relaxbeforebed:

Awarmbath,reading,oranotherrelaxingroutinecanmakeiteasiertofallsleep.Youcantrainyourselftoassociatecertainrestfulactivitieswithsleepandmakethempartofyourbedtimeritual.

Sleepuntilsunlight:

Ifpossible,wakeupwiththesun,oruseverybrightlightsinthemorning.Sunlighthelpsthebody'sinternalbiologicalclockresetitselfeachday.Sleepexpertsrecommendexposuretoanhourofmorningsunlightforpeoplehavingproblemsfallingasleep.

Don'tlieinbedawake:

Ifyoucan'tgettosleep,don'tjustlieinbed.Dosomethingelse,likereading,watchingtelevision,orlisteningtomusic,untilyoufeeltired.Theanxietyofbeingunabletofallasleepcanactuallycontributetoinsomnia.

Controlyourroomtemperature:

Maintainacomfortabletemperatureinthebedroom.Extremetemperaturesmaydisruptsleeporpreventyoufromfallingasleep.

Seeadoctorifyoursleepingproblemcontinues:

Ifyouhavetroublefallingasleepnightafternight,orifyoualwaysfeeltiredthenextday,thenyoumayhaveasleepdisorderandshouldseeaphysician.Yourprimarycarephysicianmaybeabletohelpyouifnot,youcanprobablyfindasleepspecialistatamajorhospitalnearyou.Mostsleepdisorderscanbetreatedeffectively,soyoucanfinallygetthatgoodnight'ssleepyouneed.

ForinformationonotherneurologicaldisordersorresearchprogramsfundedbytheNationalInstituteofNeurologicalDisordersandStroke,contacttheInstitute'sBrainResourcesandInformationNetwork(BRAIN)at:

BRAINP.O.Box5801Bethesda,MD20824(800)3529424www.ninds.nih.gov

Preparedby:OfficeofCommunicationsandPublicLiaisonNationalInstituteofNeurologicalDisordersandStrokeNationalInstitutesofHealthBethesda,MD20892

NINDShealthrelatedmaterialisprovidedforinformationpurposesonlyanddoesnotnecessarilyrepresentendorsementbyoranofficialpositionoftheNationalInstituteofNeurologicalDisordersandStrokeoranyotherFederalagency.Adviceonthetreatmentorcareofanindividualpatientshouldbeobtainedthroughconsultationwithaphysicianwhohasexaminedthatpatientorisfamiliarwiththatpatient'smedicalhistory.

http://www.ninds.nih.gov/



AllNINDSpreparedinformationisinthepublicdomainandmaybefreelycopied.CredittotheNINDSortheNIHisappreciated.

NIHPublicationNo.063440c

LastupdatedJuly25,2014

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