2018年6月大学英语六级听力常考时文：Factors for Colds思维导图

Acriticalfactorthatplaysapartinsusceptibilitytocoldsisage.Astudy,donebytheUniversityofMichiganSchoolofPublicHealth，revealedparticularsthatseemtoholdtrueforthegeneralpopulation.Infantsarethemostcold-riddengroup，averagingmorethansixcoldsintheirfirstyears.Boyshavemorecoldsthangirlsuptoagethree.Aftertheageofthree，girlsaremoresusceptiblethanboys，andteenagegirlsaveragethreecoldsayeartoboys’two.Thegeneralincidenceofcoldscontinuestodeclineintomaturity.Elderlypeoplewhoareingoodhealthhaveasfewasoneortwocoldsannually.Oneexceptionisfoundamongpeopleintheirtwenties，especiallywomen，whoshowariseincoldinfections，becausepeopleinthisagegrouparemostlikelytohaveyoungchildren.Adultswhodelayhavingchildrenuntiltheirthirtiesandfortiesexperiencethesamesuddenincreaseincoldinfections.Thestudyalsofoundthateconomicsplaysanimportantrole.Asincomeincreases，thefrequencyatwhichcoldsarereportedinthefamilydecreases.Familieswiththelowestincomesufferaboutathirdmorecoldsthanfamiliesattheupperend.Lowerincomegenerallyforcespeopletoliveinmorecrampedquartersthanthosetypicallyoccupiedbywealthierpeople，andcrowdingincreasestheopportunitiesforthecoldvirustotravelfrompersontoperson.Lowincomemayalsoadverselyinfluencediet.Thedegreetowhichpoornutritionaffectssusceptibilitytocoldsisnotyetclearlyestablished,butaninadequatedietissuspectedofloweringresistancegenerally.