There’snothinglikeagoodnight’ssleep—butwhatdoesthatreallymean?Itturnsoutthattheanswerdependsnotonlyonyouragebutalsoonyourlifestyle.Somepeopleareproductiveandhappywithfewerhoursofsleepwhileothersneedmore.Stillexpertscandetermineguidelinesthatworkformostpeople.TheNationalSleepFoundationresearchedthetopicandgavenewrecommendationsthisweek.Thefoundationacknowledgesthatsleepneedswillvary—lifestyleandstressshouldbetakenintoconsideration—buttheirrecommendationsofferageneralguideline.Forexampleteenagers(14—17yearsold)need8—10hours’sleepeveryday.

Tocreatetherecommendationssomesleepandmedicalexpertsreviewed312articlesfromjournalspublishedduringthelastdecade.Thisisthefirsttimethatanyprofessionalorganizationhasdevelopedage-specificrecommendedsleepdurationsbasedonasystematicreviewoftheworldscientificliterature.

Alackofsleepcanbelinkedtoweightgainbecausethatcausesanincreaseinappetiteaccordingtothefoundation.Itcanalsohaveseriousconsequencesonthebrain.Peoplewhodonotgetenoughsleepareatincreasedriskfordepressionandcanendangerothers.Thosethatbecomesleepywhiledrivingforexampleriskboththeirlivesandthelivesofthosearoundthem.

Researchersalsohavefoundinthepastthattoomuchsleepcanhavenegativeeffects.Lowsocioeconomicstatusanddepressionreportedlyaresignificantlyassociatedwithlongersleep.Howeverexpertsnowadaysfindthatresearchonoversleepingisstillunconvincingandneedsmoreattention.Currentlythereisnostrongevidencethatsleepingtoomuchhashealthconsequences.Thereishoweverlaboratoryevidencethatshortsleepdurationsoffourtofivehourshavenegativeconsequences.Weneedsimilarlaboratorystudiestodeterminewhetherlongsleepdurationsresultinphysiologicalchangesthatcouldleadtodiseasebeforewemakeanyrecommendationsagainstsleepextension.

56.WhichisTRUEaboutsleepingtime?

A.Experts’guidelineforsleepingtimeappliestoallthepeople.

B.Thetimeyouneedforsleepisrelatedtoyourstateofmind.

C.Thelessyousleepthemoreproductiveyouare.

D.Themoreyousleepthemoreener