5 Stages of Sleep & Sleep Cycles - American Sleep Association

Stage 1 Sleep. Stage 1 of the sleep cycle is the lightest stage of sleep. · Stage 2 Sleep. Stage 2 usually follow Stage 1 and represents deeper sleep. · Stage 3 ... Home-AboutSleep:Tips,QuotesandMore-StagesofSleep:TheSleepCycle StagesofSleep:TheSleepCycle Therearefivestagesofsleepduringthesleepcycle.Scientistscategorizedthestagesofsleepbasedonthecharacteristicsofthebrainandbodyduringsleep.Stage1,2,3,and4,arecategorizedas‘non-REMsleep’,andthefifthstage,isREMsleep.Generally,brainwavefrequenciesandamplitudesfromanelectroencephelogram(EEG) areusedtodifferentiatethedifferentstagesofsleep,alongwithotherbiologicrhythmsincludingeyemovements(EOG)andmusclemovements(EMG). Non-REMSleepoftheSleepCycle Stage1Sleep Stage1ofthesleepcycleisthelighteststageofsleep.TheEEGbrainfrequencyisslightlyslowerthanduringwaketime.Thereismuscletonepresentintheskeletalmuscles.Breathingoccursataregularrate. Stage2Sleep Stage2usuallyfollowStage1andrepresentsdeepersleep.DuringStage2sleep,thesleeperislessabletobeawakened.Stage2sleepischaracterizedby‘sawtoothwaves’andsleepspindles. Stage3and4Sleep–DeepSleep Stage3andStage4sleepofthesleepcycleareprogressivelydeeperstagesofsleep.Thesestagesofsleeparealsocalled‘SlowWaveSleep’(SWS),ordeltasleep.DuringSWS,theEEGshowsamuchslowerfrequencywithhighamplitudesignals(deltawaves).AsleeperinSWSisoftendifficulttoawaken.Somestudieshavedemonstratedthatveryloudnoises,sometimesover100decibels,willnotawakensomeduringSWS.AshumansgetoldertheyspendlesstimeinslowwavedeepsleepandmoretimeinStage2sleep. Slow-wavesleepisgenerallyreferredtoasdeepsleep,andiscomprisedofthedeepeststageofNREM.Instagethreeweseethegreatestarousalthresholds,suchasdifficultyinawakening,andsoon.Afterbeingawoken,thepersonwillgenerallyfeelquitegroggy,andcognitiveteststhathavebeenadministeredafterbeingawokenfromthethirdstageshowthatforuptohalfanhourorso,andwhencomparedtoawakeningsfromtheotherstages,mentalperformanceismoderatelyimpaired.Thisisaphenomenonknownassleepinertia.Whensleepdeprivationhasoccurredthere’sgenerallyasharpreboundofslow-wavesleep,whichsuggeststhatthere’saneedforslow-wavesleep.Itnowappearsthatslow-wavesleepisahighlyactivestate,andnotabrainquiescenceaspreviouslybelieved.Infact,brainimagingdatashowsthatregionalbrainactivityduringnon-REMsleepisinfluencedbythemostrecentwakingexperience Stage5Sleep(REMSleep)oftheSleepCycle Stage5ofthesleepcycle,orREMsleep,isthestageofsleepassociatedwithdreaming.Itisverydifferentphysiologicallyfromtheotherstagesofsleep.TheEEGresembleswaketime.However,theskeletalmusclesareatonic,orwithoutmovement.Thebreathingismoreerraticandirregular.Theheartrateoftenincreases.Itistheorizedthatmuscleatoniaevolvedinordertoprotecttheindividualfrominjuryduringsleep. K-ComplexesandSleepSpindles SpindleactivityisexclusivetoNREMsleep,withmostoccurringatthestartandendofNREM.Sleepspindlesengagebrainactivationinthesuperiortemporalgyri,anteriorcingulate,insularcorticesandthethalamus.Sleepspindleshavedifferentlengths;withslowspindlesassociatedwithanincreaseinactivityintheareaknownasthesuperiorfrontalgyrusrangingbetween11and13Hz,andfastspindlesassociatedwiththerecruitmentofboththehippocampusandthemesialfrontalcortexandthesensorimotorprocessingcorticalregionsrangingbetween13and15Hz.Atthispointintimeit’snotclearwhatismeantbythesesleepspindles,butit’shopedthatongoingresearchwillrevealtheirfunction. DefiningK-Complexes K-ComplexesarealsoexclusivetoNREMsleep,andcanbedefinedassinglelongdeltawaveslastingforonlyasecond.Likesleepspindles,theyappearautomaticallyduringtheearlystagesofsleep,generallyinstagetwo.However,K-Complexescanbeinducedatwillbymomentarynoises,suchassomeoneknockingonadoor.FurtherresearchmustbeconductedonK-Complexesbecausetheirfunctioniscurrentlyunknown. DreamingduringNREM DuringREMsleep,studyparticipantsreportedbothintensedreamvividnessandimprovedmemoryofdreamswhichoccurredduringthatphase,whichsuggeststhatdreamingtypicallyoccursREMsleep:weknowthatdreamingalsooccursduringNREMsleep;however,incomparison,thesedreamsappeartobemoremundane.WealsoknowthatdreamsthatoccurduringtheNREMstageofsleeptypicallyoccuraftermidnight,whichhappenstobethetime-periodwiththehighestrateofREMsleep.Thiswasdiscoveredbyastudywherebysubjectstooknapsoverspecificperiodsoftimeandwerethenforcefullywoken:sleepwasdividedinto– napswithonlyREMsleep,and napswithonlyNREMsleepusingpolysomnography. TheimplicationhereisthattheoccurrenceofREMsleepisnotnecessaryfordreaming,butratherthattheactualprocessescreatingREMsleepresultinalterationstoaperson’ssleepexperience. Bymorning,andbecauseofthesechanges,thereoccursasub-corticalactivationthat’scomparabletotheonethatoccursduringREMsleep.Therefore,duringthemorninghoursintheNREMstageit’sthesub-corticalactivationthatcausesdreaming. Non-REMMuscleMovements  Thetonicdrivetothemajorityoftheupperairway’srespiratorymusclesisrepressedduringnon-REMsleep,withthefollowingconsequences– Duetotheintracellularcalciumlevelsbeinglowered,weakenedmusclecontractionsarecausedbyrhythmicinnervation.Motoneuronsarehyperpolarizedbytonicinnervationbeingremoved. There’sa‘floppiness’intheupperairway. Thediaphragmistypicallydrivenbytheautonomoussystemandisthereforenormallysparednon-REMinhibition,andassuch,thesuctionpressuregeneratedstaysthesame.Theupperairwayisthusnarrowedduringsleep,whichincreasesresistanceandmakesupperairwayairflownoisyandturbulent.Asweknow,wedeterminethatapersonisasleepbylisteningtotheirbreathing:theirbreathingbecomesdistinctlylouderoncetheyfallasleep.So,it’snotsurprisingthattheupperairway’sincreasedtendencytocollapsewhilebreathingduringsleepleadstosnoring,whichissimplythetissuesvibratingintheupperairway.Foroverweightpeople,thisproblemisaggravatedwhentheysleepontheirbackbecauseexcessfattissuecaneasilypushdownandclosetheairway.Thiscanultimatelyleadtosleepapnea. Eachsleepstageservesauniqueroleinbrainandbodyrestoration.Therearemanysleepdeprivationstudiesthathavedemonstratedthatdeprivingsubjectsofspecificsleepstagesofthesleepcyclehasanadverseeffectonbodyandbrainfunctions. AuthorRecentPostsASAAuthors&ReviewersSleepPhysicianatAmericanSleepAssociationReviewersandWritersBoard-certifiedsleepM.D.physicians,scientists,editorsandwritersforASA.LatestpostsbyASAAuthors&Reviewers(seeall) HowDoestheSunImpactSleep?-November22,2021 HowPostureAffectsSleepQualityinAdultsandChildren-November18,2021 Sleepvs.Rest:What’stheDifference?-October22,2021 Relatedposts: SleepDeprivationEffectsontheBrain Easiestwaytofallasleep Snoring Narcolepsy NarcolepsySymptoms 13thoughtson“StagesofSleep:TheSleepCycle” Ididn’tseeanymentionofhowlongthesesleepstageslast.Withoutknowingthat,Ican’trelatemysleepproblemstothesecycles. sotrue!!! I’mcuriousabouttheeffectsofcaffeineonstages3-5ofsleep. Iaveragelessthananhourofdeepsleep.Sometimesonlyabout20min.Therestis2xlightsleepcomparedtoremsleep.Isthisaverage? Iama75yearsoldwomanwithasthma.In2019Ihavebeendiagnosedwithsleepapnea,evenifIneverhadthesomnolencewhichistypicalforitand,accordingtomyhusbandamsnoring,butwithoutthetypicalnoises.Onthecontrary,Iamagreatinsomniac:inordertosleep6hourspernightIneedtotakeImovane(75mg)plussomenaturopaticdrugscontaininghydroxytriptophan,melatonin,GABAandtheanine.WiththeCPAPmyinsomniahasincreaseddramatically:after5-6daysofCPAPtreatmentIcannotsleepatallevenwiththedrugs,and,inordertogettomynormal,Ineedtotakeapauseofseveraldays.IwouldliketoknowwhetherCPAPcanhavenegativeeffectsonasthmaandwhetheritproducesadeclineintheREMpartofthesleep.IwouldgreatlyappreciateyouradviseregardingmytreatmentwithCPAP Sincerely, Dr.MarianaCiureanu Sleeptechnicianhere.IseemanypatientswhoseinsomniasymptomscanbecomemuchworseifCPAPpressuresarenotcorrectlyset.AskyourhusbandtowatchyouonenightwhilewearingyourCPAPtoseeifyouhavewhatiscalledTreatmentEmergentCentralSleepApnea.CentralSleepApneaisbasicallywhenyoustoptryingtobreatheentirely.IfyourCPAPpressureistoohigh,itmaybecausingyoutostopbreathing(notduetoanobstructionthough),andIseealotofinsomnia,specificallysleep-onsetinsomnia,toberelatedtocycliccentralapneaswhenfallingasleep.Fallasleepfor5seconds,stopbreathing,wakeupfor5seconds,fallasleepfor5seconds,stopbreathing,etc.Even5minutesofthiscansubjectivelyfeellikeyou’vebeenawakeforhours.Askyourdoctortoseeifyoucanhaveanin-labstudywithyourcurrentCPAPsettingstoseewhat’shappening;properCPAPsettingsshouldnevermakeyoursleepfeelworse.Hopethishelpsyouandothers! Doyouansweranycomments? WhywakestageisnotincludeI’mdoingasleepstudyresearchandIdidnotfindwakestagehere. I’mdoingresearchforsleepstudyandyoudidnotincludewakestage. Icansleepnotmorethenhalfanhour. Whatchemicals/hormones(?)areinvolvedinallowingthebodytogointodeepsleep?ForexampletofallasleepGABAneedstorise,histamineandglutamatelevelsneedtofallandthatletsusfeelsleepy.InthemorningGABAlevelsreduceandhistaminelevelsriseandwe‘wake’.Whatisinvolvedingoingintothedeepssleepstage?? Howdoyougetmorestagesofsleep? Sinceyoumention‘delta’sleep,youmightaswellmentiontheothersynonymsfortheotherstages:alpha,beta,theta–afterthewaveformsseenintheEEG. LeaveaReplyCancelreplyYouremailaddresswillnotbepublished.Requiredfieldsaremarked*Comment*Name Email Notifymeofnewpostsbyemail. 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