Brit.J.industr.Med.,I967,24,i8i.PhysiqueandSerumLipidsofYoungLondonBus - PDF document

Brit.J.industr.Med.,I967,24,i8i.PhysiqueandSerumLipidsofYoungLondonBusmeninrelationtoIschaemicHeartDiseaseR.M.OLIVER'FromLondonTransportBoardEarlierstudiesofwhiteLondonbusmenrevealedthattheischaemicheartdiseaseexperienceofcon-ductorsisbetterthanthatofdrivers.Variousfactorswhichmightberelatedtothisdifferencehavebeenconsidered,andearlierinvestigationshaveestablishedthatthephysiqueandserumlipidconcentrationsofmeninthesetwooccupationsaredifferent.Sincemenintheyoungeroccupationalgroups(25tO29years)showedsomeofthesedifferencesthesuggestionhasbeenmadethatconductorsmaybeconstitutionallydifferentfromdrivers.Thepurposeofthispaperistoreportastudyofthephysiqueandserumlipidconcentrationsofyoungrecruitsforbusdrivingandconductingatanearlieragethaninpreviousstudiesandbeforeanyoccupationalfactorscouldhaveexertedaneffect.Physicaldifferencesbetweenthetwogroupsofrecruitswereshowntoexist.Britishbusdriverrecruitsintheagegroup21to24yearswereonaverage2-6cm.tallerthanBritishconductorrecruits.Thisisprobablybecauseselectionfavourstherecruitmentoftallermenfordriving.Newentrantdriverswereonaverage73lb.(33kg.)heavier,approximatelyicm.broaderacrosstheshoulders,andbetween2and3cm.biggerroundthechestsandwaiststhanconductors.Itisshownthatthesedifferencesaremainlysecondarytodifferencesinheight.Driversrecruitedfromtheranksofexistingconductorsresemblednewentrantdriversineverythingbutheight.Britishdrivertraineescarriedmoreskinfatandhadatendencytohigherserumlipidconcentrationsthanconductors.Thisisshowntobeneithersecondarytodifferencesinheightnoroccupationallyacquired.Theimportanceofthesefindingsinrelationtothedifferingischaemicheartdiseaseexperienceofbusdriversandconductorsisdiscussed.ItissuggestedthattheunderlyingfactorresponsiblefortheknownlaterphysicaldifferencesanddifferentischaemicheartdiseaseexperienceofLondonbusdriversandconductorsmightbeacommongeneticone.PreviousinvestigationsintothehealthandcharacteristicsofLondonbusdriversandmaleconductorshaveshownthattherearecertainphysicaldifferencesbetweenthetwogroups.Thishasbeendeterminedbystudyingexistingemployees(Morris,Heady,Raffle,Roberts,andParks,I953;Morris,Heady,andRaffle,I956;Heady,Morris,Kagan,andRaffle,I96I).Londonbusconductorsarelesslikelythandriverstodevelopischaemicheartdiseaseandarelesslikelytodiesuddenlyfromthedisease(Morrisetal.,I953;MorrisandRaffle,1954).Morrisetal.(I953,I956)discussedtherelationshipofthisdifferingischaemicheartdiseaseexperienceofLondonbusmentothedifferingexertionalrequire-mentsandthephysicalcharacteristicsofmeninthetwooccupations.TheywereabletodemonstratethatthebuildsofLondonbusdriversweredifferentfromthoseofconductors.Driverswereonaveragetaller,heavier,stouter,andcarriedmoreskinfatthanconductors.Therelationshipbetweenthesephysicalfindingsandheartdiseaseinbusmenwas,however,notclear.Headyandhiscolleagues(I96I)showedthatsurvivorsofischaemicheartdiseaseepisodesamongdriversandconductorsdidnotmateriallydifferphysicallyfromthoseinthesameoccupationwhohadnothadthedisease.Bodybuildisinfluencedbymanyfactors,oneofwhichisundoubtedlyphysicalactivity.ThestudiesofMorrisandhiscolleaguesonbusmenandotherworkers(Morris,I960;Morrisetal.,I953;MorrisandCrawford,I958;Morris,Kagan,Pattison,ReceivedforpublicationJanuary6,I967.'Presentaddress:TreasuryMedicalService(PostOfficeBranch),ArmourHouse,St.Martin's-le-Grand,London,E.C.I.I8I GardnerandRaffle,I966),coupledwiththoseofmanyotherinvestigators(Stocks,195I;BrunnerandManelis,I960;Zukel,Lewis,Enterline,Painter,Ralston,Fawcett,Meredith,andPeterson,I959;Karvonen,Rautaharju,Orma,Punsar,andTakkunen,I96I;Kahn,I963),leavelittledoubtthatphysicalactivityhasanimportantbeneficialrelationshiptoischaemicheartdisease.Thus,althoughphysicalactivityseemstohaveanimport-antfavourableinfluenceonischaemicheartdiseaseinLondonbusconductors,thepartplayedbyphysiqueisnotcertain.Furthermore,howfararethedifferencesinphysiquebetweenestablisheddriversandconductorsthemselvessecondarytothedifferentphysicalactivityinthetwogrades?Headyandhiscolleagues(I96I)showedthatdriversaged25to29yearswereissuedwithbiggeruniformsthanconductors,andthisledtothesuggestionthattherewerepre-existingconsti-tutionaldifferencesbetweendriversandconductors.Thissuggestionwas,however,basedonthefindingsinmeninwhomtheinfluenceofoccupationalfactorscouldnotberuledout.Conductors,forexample,intheagegroup25to29yearscouldhavebeenemployedonthisworkforuptoI2years.Itwas,therefore,importanttoexamineinmoredetailthepossibilityofpre-existingphysicaldifferencesinyoungbusdriversandconductorsbeforetheeffectsoftheirrespectiveoccupationscouldsignificantlyinfluencethefindings.Itwasthepurposeofthepresentstudytodeter-minebydirectclinicalmeasurementwhetheryoungrecruitsforbusdrivingandconductingexhibiteddifferencesinbodybuilds;toestablishwhatwerethephysicaldifferences,ifany;andtoconsiderwhetherthesedifferencesmighthaveabearingonthedifferingischaemicheartdiseaseexperienceofmeninthesetwooccupations.BecauseoftherelationshipofserumlipidstocertainaspectsofbodybuildandtheirpossiblerelationshiptoischaemicheartdiseaseinLondonbusmen(Morris,1959;Kagan,I960),serumlipidestimationswerealsoundertaken.MethodTheinvestigationwascarriedoutonwhitemenselectedfortrainingbyLondonTransportasbusdriversorbusconductorsduringI960andI96I.ItwassubsequentlyextendedtoincludesomementrainingintheearlypartofI964.Themenweremainlynewentrantemployeesbutsomedrivertraineeswhohadpreviouslybeenemployedasconductorswerealsoincluded.BeforeenteringLondonTransportTrainingSchooleverymanisrequiredtopassaninitialinterviewandmedicalexamination.Afairlyhighstandardofphysicalfitnessisnecessaryandcertainphysicalstandardsarelaiddown.Inaddition,newentrantdriversarerequiredtopassapreliminarydrivingtesttoensurethattheypossessthebasicqualitiesnecessarytodrivebuses.Thusitisseenthatthemenwhofinallyundergotrainingareaselectedgroupofindividuals.Forthepurposesofthisinvestigationtherewasnopracticalwayofovercomingthisdifficulty.ArandomsampleofwhitemalerecruitsandtransferstothegradeofbusdriverandbusconductorintheCentralRoadServices(redbusesofLondonTransportBoard)wasselected.Theselectionwasbasedonthedayofthemonthinwhichtheindividualwasborn.Themenwereallwithintheagerange2Ito24yearsinclusive.Thisparticularagerangewaschosentoenablesufficientnumbersofmentobecompared,bearinginmindthattheyoungestagepermittedforaLondonTransportbusdriverwas2Iyears.Newentrantdriversarerequiredtohavehadsomepreviousexperienceofdrivingwhereasconductorstransfer-ringtothegradeofdriversarenotrequiredtohavehadanysuchexperience.Themencould,there-fore,bedividedintothreegroups:(i)newentrantdrivers-menwhowouldliketobeLondonbusdriversandhavehadsomepreviousdrivingexperience;(2)transferdrivers-menwhowereLondonbusconductorsbutwantedtobebusdrivers.Thesemendidnotnormallyhavemuchdrivingexperience;and(3)newentrantconductors-menwhopreferredtobeconductors.Thenewentrantconductorgroupmayalsohaveincludedafewmenwho,becausetheylackedpreviousdrivingexperience,hopedtobecomedriverslateron,ormenwhowerebelowthemedicalstandardsfordriving.Theinclusionofsuchmeninthisgroupwould,however,haveadilutingeffectonanyconductorcharacteristicsandwasnot,therefore,consideredtoaffectsignificantlythecomparisons.Sometransferdriversmayhaveappliedfortrainingasdriverssimplybecausetheydislikedconductingorforsomeotherreasonunconnectedwithaspecificwishtodrive.Suchmenwouldalsohaveadilutingeffectonanycharacteristicsassoci-atedwithaspecificpreferencefordrivingwhichmightbeexhibitedbythetransferdrivergroupasawhole.Thiswasnot,therefore,thoughttohaveanimportanteffectonanygroupcomparisons.Duringthecourseoftheinvestigationitwasdiscoveredthatmanyoftherecruits,particularlytheconductors,wereofSouthernIrishnationalityprobablywiththeirownnationalcharacteristics.ThiscouldhaveaffectedthecomparisonsmadeI82.R.M.Oliver PhysiqueandSerumLipidsofYoungLondonBusmeninrelationtoIschaemicHeartDiseaseI83betweengroups.MenfromSouthernIrelandwere,therefore,excludedfromtheinvestigationandthisstudyisconfinedtowhiteBritishtrainees.Toavoidbiasthephysicalexaminationwascarriedoutwithoutpriorknowledgeoftheman'sintendedoccupation.Thefollowingdatawererecorded:(a)heightwithoutshoes(b)sittingheight.Thiswasmeasuredwiththesubjectseatedandisthedistancebetweentheplaneoftheseatandthetopofthehead(c)weight(d)chestcircumferencemeasuredatfullinspir-ationandfullexpirationapproximately2cm.belowthenipples(e)waistcircumferencemeasuredattrouserwaistlevelwiththesubjectstandingrelaxedandbreathingnormally(f)bi-acromialdiameter.Thisisthedistancebetweenthetipsoftheacromialprocesses(g)skinfoldthickness.ThiswasmeasuredusingHarpendenskinfoldcalipers(TannerandWhite-house,1955)atthreesites-triceps,subscapular,andsupra-iliac(h)serumlipids(i)totalcholesterol(bythemethodofAbell,Levy,Brodie,andKendall,I952)(2)lowdensitylipoproteins;amodifiedultra-centrifugalmethod(LindgrenandGofman,1957)usingrefractiveindexincrementI5Ixio-3/g./iooml.(HanigandShainoff,1956)(3)calculationoftheconcentrationofmoleculesSf.0-I2andSf.I2-400using(2)andthetotalcholesterolinthelowdensityfractionintheregressionequationssuppliedbyLindgrenandGofman(I957).ResultsAtotalof228Britishtraineeswasexamined.AsummaryoftheresultsisshowninTableI.ThestatisticalanalysisappearsinAppendixTablesIandII(pp.I87andi88).HeightandWeightNewentrantdriverswere26cm.talleronaveragethannewentrantconduc-tors(P=o-oi),mostofthisincreasedheightbeingaccountedforbyincreasedleglength.Transferdriverswerenottallerthanconductors.Newentrantdriverswereonaverage7-3lb.(3.3kg.)heavier(P=o-oI),andtransferdrivers4-2lb.(I9kg.)heavier(P=o02I),thannewentrantconductors.GirthDriverswereshowntobebiggerroundthechestandwaistthanconductors.ThemeanTABLEIDIFFERENCESINPHYSIQUEANDSERUMLIPIDSBETWEENGROUPSOFTRAINEEBUSMEN(MEANSROUNDEDTONEARESTWHOLENUMBER)NewTransferNewEntrantDriversEntrantDriversConductorsHeight(cm.)175173I73Sittingheight(cm.)939292Weight(lb.)I52I49144(kg.)696866Chestcircumference(cm.)Inspiration929290Expiration868584Waistcircumference(cm.)781875Bi-acromialdiameter(cm.)404039Skinfoldthicknesses'(mm.)Triceps777SubscapularIOII9Supra-iliac997Total272924SerumlipidsCholesterol(mg./iooml.)195195187Lowdensitylipoproteins(mg./Iooml.)5II498486FractionSf.O-I2(mg.)315318310FractionSf.12-400(mg.)I89I76I76Nos.ofobservationsandstatisticalanalysisareshowninAppendixTablesIandII(pp.I87andI88).'Totalskinfoldthicknesseswerederivedfromthesumoftheotherthreeskinfolds.ThicknessestransformedusingformulaZ=IOOloglo(readinginO-Imm.minusI8)(Edwards,Hammond,Healy,Tanner,andWhitehouse,1955).circumferencesofthechestsofnewentrantdriverswereonfullinspiration2-2cm.greaterandonfullexpiration2-7cm.greaterthanthoseofnewentrantconductors.Boththesedifferencesarestatisticallysignificant(P)Similarly,theinspiratoryandexpiratorychestcircumferencesoftransferdriverswererespectivelyI7cm.andix8cm.greaterthanthoseofconductors(P=o-o6ando-o5).Themeanwaistmeasurementsofnewentrantandtransferdriverswererespectively26cm.and29cm.greaterthanthoseofconductors(P=o-o2inbothinstances).ShoulderBreadthThetwodrivergroups,asjudgedbythebi-acromialdiameter,werebroaderacrosstheshouldersthanconductors,thedifferencebeingapproximatelyicm.ineachinstance.Althoughthedifferencewassmallitneverthelessishighlysignificantstatistically(P=0o0002). SkinfoldThicknessesDrivers,especiallythetransferdrivers,hadgreatermeanskinfoldthick-nessesthanconductors.Thiswasmostmarkedforthesubscapular,supra-iliac,andtotalskinfolds.Thedifferencesbetweenanyofthetricepsskinfoldthicknessesarenotstatisticallysignificant.SerumLipidsNoneofthedifferencesisstatisticallysignificant.Previousstudies(Morris,I959;Kagan,I960)hadsuggestedthatahigherconcentrationofserumcholesterolmightbeexpectedinthedrivergroupsanditisnoteworthythat,despitetheabsenceofstatisticalsignificance,theresultsinthisstudyfollowedtheexpectedpattern.DiscussionItisseenthatthereareimportantphysicaldifferencesbetweenyoungbusdriverandconductorrecruits.Driverswerebiggerroundthechestandwaistthanconductorsandwerebroaderacrosstheshoulders.Driverswereheavierthanconductorsbutthedrivertraineeswhohadpreviouslybeenconductors(thatisthe'transfer'drivers)wereonlyslightlyheavier.Anotherimportantcharacteristicwasthatthedrivershadmoresubcutaneousfatthantheconductors.ThisiscommontothenewentrantandtransferdriversandisunlikelytobetheresultofanyselectionbyLondonTransport.Theincreasedmeanserumlipidconcentrationsofbothdrivergroupsareprobablyrelatedtoincreasedobesity.Minordegreesofobesity,therefore,seemtobeassociatedwithapreferencefordrivingratherthanconductingbuses.Eventhosemoreobesemenwhoarealreadyconductorsbecausetheyarenotoldenoughorlacktheexperiencetobecomedriversalsochoosetotrainasdriverseveniftheyhaveneverintheirlivesdrivenbefore.Thereasonforthisisnotknown.Itmaybeanassociatedinherentwishforajobinvolvinglittleexertionorsomeasyetundeterminedpsychologicalcharacteristicwhichmakesamanseekajobawayfromclosecontactwithotherpeople.Possiblyitisadesiretobe'incharge'orsimplyambition,sinceforaconductortobecomeadriverispromotion.Theheightofnewentrantdriverswassignificantlygreaterthanthatofconductors.Ontheotherhand,themeanheightoftransfer'driverswasalmostidenticalwiththatofconductors.Thus,althoughinmanyoftheotherphysicalfactorsthetransferdriverscloselyresemblednewentrantdrivers,inheighttheyshowedamarkedandstatisticallysignificantdifferencefromtheirnewentrantcolleagues(Pos).Fromthisitseemslikelythatheightmayplayanimportantpartinthepreliminaryselectionforemploymentofdriversandconductors.ItwasthepolicyofLondonTransporttorejectforemploymentasconductorsmenwhowereover6ft.(i8m.)tall.Driversmustbeabletoreachthedrivingpedals.Thismayinfluencetheselectionoflonger-leggedmenfordrivingwithaconsequentgreateroverallmeanheightforthisgroup.Thedataobtainedfromthenewentrantdrivergroupinthisstudysupportedthisview.Thus,tall,long-leggedmenareselectedorselectthemselvesforinitialrecruitmentasdriversandtallmenarerejectedordonotapplyforemploymentasconductors.Thisexplainswhytransferdrivers,whohadfirstbeenselectedandservedasconductors,resemblednewentrantconductorsintheirmeanheight.Itisimportanttoconsiderhowfarheightselectionmayberesponsiblefortheotherphysicaldifferencesbetweendriversandconductors.Clearly,itisnotanimportantfactorinexplainingtheotherdifferencesbetweentransferdriversandconductorsasthemeanheightsofthesetwogroupsweresimilar.Itappearedthatthefatter,stouter,broaderconductorsliketobecomedrivers.Inthenewentrantdriverswheretheinfluenceofheightonothercharacteristicscouldbeimportantitwasthoughtadvisabletocomparenewentrantdriversandconductorsofsimilarheight.Inthisstudysufficientnumbersforausefulconclusiontobedrawnwereobtainedbycomparingmenwithinanintermediateheightrange,thatis,menwhoseheightwasI73cm.ormorebutlessthani8ocm.Themeanheightsofdriversandconductorswithinthisheightrangedifferedbyonly03cm.,whichwasnotsignificant&#xo Tj;&#x /F1;&#x 11.; T; 53;&#x.60 ;&#xTz 2;.72;&#x 0 T; 00;(Po5).TheresultsofthecomparisonmadeinthiswayareshowninTableIIandAppendixTableIII(p.i88).Incontrasttothetransferdriversthenewentrantdriversdidnotshowsuchmarkeddifferencesfromconductorsofsimilarheight.Themeanchestandwaistcircumferencesandthebi-acromialdiameterofnewentrantdriverswereonlyslightlygreaterthanthoseofconductorsofsimilarheight.Thedifferencesarenotstatisticallysignificant.Sim-ilarly,newentrantdriverswereonlyI-3lb.(o-6kg.)heavierthanconductorsinthisintermediateheightrange.Thisalsoisnotstatisticallysignificant.Theskinfoldthicknessesdid,however,showmarkeddifferences.Newentrantdriverscarriedconsider-ablymoreskinfatthannewentrantconductorsofsimilarheight.Thisdifferenceofnearly5mm.inthetotalofthethreeskinfoldsisstatisticallysignificant(P)Theincreasedskinfati84R.M.Oliver PhysiqueandSerumLipidsofYoungLondonBusmteninrelationtoIschaemicHeartDiseasei85TABLEIIDiIENcEsINIMPORTANTPHYSICALCHARAcTERIsTIcsBETwEENNawENTRANTDRIVERSANDCONDUCTORSWITHNTEHEIGHTRANGE173CM.TOi8oCM.(MEANSROUNDEDTONEARESTWHOLENUMBER)NewNewEntrantEntrantDriversConductorsHeight(cm.)I75I75Chestcircumference(inspiration)(cm.)929IWaistcircumference(cm.)7776Bi-acromialdiameter(cm.)4040Weight(lb.)I49I48(kg.)6867Totalskinfoldthickness(mm.)23I9Serumcholesterol(mg./iooml.)I95I82ThefullresultsandstatisticalanalysisareshowninAppendixTableIII.TotalskinfoldasinTableI.probablyexplainsthegreatermeanweightofnewentrantdriversinthisgroupandisalsolikelytobeinpartresponsibleforthedifferenceinchestandwaistcircumferencesandinshoulderbreadth.Itisofinterestinthesemenofsimilarheightsthattheserumcholesterolofnewentrantdriverswasnoticeablygreaterthanthatoftheconductors.Thedifferenceisnotstatisticallysignificantbutisgreaterthanthatdemonstratedwhenallconductorsanddriversirrespectiveofheightarecompared.Itisalsonoteworthythatthemeanserumcholesterolofthisintermediateheightgroupofnewentrantdriverswasthesameasthatofthetransferdrivergroup.ConclusionsItisapparentthatBritishmenwithcertainphysicalcharacteristicschoose,orarechosen,tobecomedriversasopposedtoconductors.Themostobviouscharacteristicgoverningthischoiceistheheightoftheindividual.Itisthiswhichisresponsiblefortheselectionasnewentrantdriversofthetaller'bigger'men.Heightisnotimportantintheselectionofdriversfromtheranksofexisingconductors.Suchtransferdrivertraineesshowmanyoftheotherphysicalcharacteristicsoftheirnewentrantcolleagues.Thusthemore'stocky'conductorstendtotransfertodrivingduties.Thepresentstudysuggeststhatthedifferencesinphysicalcharacteristicsofbusdriversandconductors,whichMorrisandhiscolleaguesdemonstratedtobepresentinolderemployees,arealreadypresenttosomeextentinmenbeforetheytakeuptheiremployment.Skeletalbuild,partic-ularlyheight,isalmostcertainlygeneticallydetermined.Thisgeneticinfluencemay,therefore,befundamentallyresponsiblefortheselectionoftallermenasdrivers.Similarly,bi-acromialdiameterismainlyaskeletalfactorprobablygeneticallydetermined.Perhapsofgreatersigni-ficanceinrelationtoischaemicheartdiseaseisthefactthatmenwithgreateramountsofskinfatirrespectiveofheightprefertobecomedrivers.Thisobesityisclearlynotoccupationallyacquiredsinceconductorswhowishtobedriversalsoshowthisfeature.Itisprobablyaconstitutionalcharacteristicoftheindividual,althoughitisnotpossibletoruleouttheeffectofpreviousoccupationbeforejoiningLondonTransport.Itisinterestingtonotethatsmallbutasyetinsignificantdifferencesintheserumlipidsofdriversandconductorswerebeginningtoappearinlinewiththoseknowntoexistinolderbusmenandatatimewhenthedifferingexertionalandotherrequirementsoftheiroccupationscouldnothavehadaneffect.Sinceobesityandraisedserumcholesterolarerelatedtoagreaterincidenceofischaemicheartdisease,thesefindingsmayhaveabearingonthesubsequentdifferingischaemicheartdiseaseexperi-enceofbusdriversandconductors.Whateverthereason,whetheritbeself-selectionorselectionbytheemployerorsomeotherunknownfactor,ithasbeenshownthatBritishyoungmenintheirearly20swhowishtostartdrivingbusesarephysicallydifferentfromthosewhoprefertobeconductors.Itislikelythatthesepre-existingdifferences,andnotlateroccupationalfactors,arefundamentallyresponsiblefortheknownphysical.differencesinolderemployees.Itissuggested,andthereissomeevidencefromthisstudy,thattheunderlyingfactorisgenetic.Ifthisisso,thenthisfactorcouldalsobefundamentallyresponsibleforthedifferingischaemicheartdiseaseexperienceofmeninthesetwooccupationsevenifvariousenvironmentalinfluencessuchasphysicalactivitylateraccelerateorretardtheprocess.Althoughoccupationmaypredisposetoischaemicheartdisease,thisstudysupportsaviewthatinheritedcharacteristics,oneofwhichmaybesusceptibilitytoheartdisease,maypredisposetoaparticularoccupation.IshouldliketothankDr.L.G.Norman,ChiefMedicalOfficer,LondonTransportBoard,forpermis-siontoundertakethisstudyandformuchencouragementandadvice.Iamalsogratefulfortheco-operationoftheStaffandWelfareOfficerandmanyotherofmyformercolleaguesinLondonTransport,particularlyMr.J.S.Chapmanforhishelpwiththestatisticalanalysisoftheresults. R.M.OliverIshouldliketoacknowledgetheassistanceofProfessorA.C.DornhorstandDr.T.R.Pilkington,ofSt.George'sHospitalMedicalSchool,withthebloodexaminationsandtothankProfessorJ.N.Morris,oftheMedicalResearchCouncil'sSocialMedicineResearchUnit,forhisadvice.ThispaperisbasedonsomeofthematerialusedinthepreparationofathesisacceptedfortheM.D.degreeoftheUniversityofLondon.REFERENCESAbell,L.L.,Levy,B.B.,Brodie,B.B.,andKendall,F.E.(1952).J.biol.Chem.,I95,357.Brunner,D.,andManelis,G.(I960).Lancet,2,1049.Edwards,D.A.W.,Hammond,W.H.,Healy,M.J.R.,Tanner,J.M.,andWhitehouse,R.H.(i955).Brit.J.Nutr.,9,133.Hanig,M.,andShainoff,J.R.(I956).J.biol.Chem.,219,479.Heady,J.A.,Morris,J.N.,Kagan,A.,andRaffle,P.A.B.(I96I).Brit.J.prev.soc.Med.,15,143.Kagan,A.(I960).Proc.roy.Soc.Med.,53,18.Kahn,H.A.(I963).Amer.J.publ.Hlth,53,1058.Karvonen,M.J.,Rautaharju,P.M.,Orma,E.,Punsar,S.,andTakkunen,J.(I96I).J.occup.Med.,3,49.Lindgren,F.T.,andGofinan,J.W.(I957).Bull.Schweiz.Akad.med.Wiss,13,152.Morris,J.N.(i959).Arch.intern.Med.,104,903.(I960).Mod.conc.cardiovasc.Dis.,29,625.,andCrawford,M.D.(I958).Brit.med.J.,2,I485.-,Heady,J.A.,andRaffle,P.A.B.(I956).Lancet,2,569.-,-,-,Roberts,C.G.,andParks,J.W.(I953).Ibid.,2,I053,IIII.-,Kagan,A.,Pattison,D.C.,Gardner,M.J.,andRaffle,P.A.B.(I966).Ibid.,2,553.-,andRaffle,P.A.B.(1954).Brit.Y.industr.med.,11,260.Stocks,P.(I95I).Lancet,I,351.Tanner,J.M.,andWhitehouse,R.H.(i955).Amer.J.phys.Anthrop,n.s.,13,743.Zukel,W.J.Lewis,R.H.,Enterline,P.E.,Painter,R.C.,Ralston,L.S.,Fawcett,R.M.,Meredith,A.P.,andPeterson,B.(I959).Amer.J.publ.HIth,49,I630.(Appendixpp.187andI88)I86 PhysiqueandSerumLipidsofYoungLondonBusmeninrelationtoIschaemicHeartDiseaseI87APPENDIXTABLEIPHYSIQUEANDSERUMLIPIDSOFTRAINEEBUSMENHeight(cm.)Chest(cm.)Bi-SerumLowFractionFractionacromialChol-DensitySf.Sf.SittingStand-WeightInspir-Expir-WaistDiametersesterolLipo-0-1212-400ing(lb.)ationation(cm.)(cm.)(mg./proteins(mg.)(mg.)I00Ml.)(mg.si00ml.)NwEntrantDriversv.NewEntrantConductorsDriversMeanStandarddeviationConductorsMeanStandarddeviationIDifrencebetweenmeans(divers-conductors)tProbabilityof't'occurringbycbanceifnorealdifference(P)92-9175-42-96-49I-9I72-82-96-o+I-O+2-6+2-23+2-740-03O0OITransferDriversv.NewEntrantConductorsTransfersMean919172-9Standarddeviation2-44-9ConductorsMean9I-9I72-8Standarddeviation2-96-oDifferencebetweenmeans(transfers-conductors)ooo+01Io'tO0oo+010Probabilityof't'occurringbychanceifnorealdifference(P)1000-92NeEntrantDriversv.TransferDriversDriversMeanStandarddeviationTransfersMean4.StandarddeviationD^rencebetweenmeans'Afivers-transfers)tProbabilityof't'occurringbychnceifnorealdifference(P)92-9175-42-96-4919I72-92-44-9+1I0+2-5+2-09+2-450-40-0292-95.390-05.I+2-2+2-77O-OI86-35.683.64.8+2-7+3-38O0OOI151-720-8I44.4'7.4+7-3+2-48O0OI148-620-6I44.4I7.4+4-2+1250-2115I-720-8148-620-6+3.I+o-86O03791.78545-05-490-083-65.I4.8+17+I-8+I-88+I-98o-o60-0577.77.575.'I6-i+2-6+2-460-0278-o7.375.I6-I+2-9+2-440-0277.77.578-o7.3-0.3-0-230-8239.92.539.''.5+o-8+2-460-02401II.439.II.5+I-OO+3-8I0-000239.92.540-II.4-0-2-0-560-58194-838.9I87-334-0+7-5+I-34o-i8194-633-6I87-334-0+730-24I94-838.9I94-633-6+0-2+0-03o-985IO-7I34-9486.3I53-I+34-4+o8-4040498-II40-5486-3153-I+II-8+0-380-70510-7I34-9498-II40-5+I2-6+0-47o-64314-848.2309-75I.5+5.I+0-5Io-6i31755I5309-7515+7-8+0-720.47314-848-231755I.5-2.7-0-27O079I88-69I-8176-0IOI-4+1I2-6+o-640-52175-996-4176-0IOII-4-011I-0-0050-99I88-69I-8I75-996-4+12-7+o-680-5092-25.39I.75-086-35.685-45-4+0-5+0-9+0-56+0-940-580°34.:Nos.ofobservations:newentrantdrivers,97;transferdrivers,52;newentrantconductors,79(exceptforserumcholesterolestimationswherethenumberswere87,50,and79respectively,andforthelipidfractions57,49,and44respectively). i88R.M.OliverTABLEIISKINFOLTDTHICKNESSESOFTRAINEEBUSMENUSINGTRANSFORMATIONIooLOG..(READINGIN0-IMM.-I8)TricepsSubscapularSupra-iliacTotalSkinfoldSkinfoldSkinfoldSkinfold(mm.)(mm.)(mm.)(mm.)NewEntrantDriversv.DriversNewEntrantConductorsMean7-4(I74-9o6)10-3(I93-33I)8-9(i85-404)26-6(232-799)Standarddeviation24-244I9.4I530'77225-938ConductorsMean6-7(i68-7I9)9-3(i87-425)7-2(17337I)23-5(225-900)Standarddeviation2I359I797829-o822I07IDifferencebetweenmeans(drivers-conductors)0-7(6-I87)I-O(5-906)I-7(I2-033)3-I(6-899),t'I*7642-06I2-629I*894Probabilityof't'occurringbychanceifnorealdifference(P)o-o800-4001o*o6TransferDriversv.TransfersNewEntrantConductorsMean7-3(I74-279)II-4(i98-407)9-2(I86-896)28-6(236-532)Standarddeviation22-II820'4593I-62723-052ConductorsMean6-7(I68-I79)9.3(i87-425)7-2(I7337I)23-5(225-900)Standarddeviation2I*359I7-97829-02821-07IDifferencebetweenmeans(transfers-conductors)o-6(5-56o)2-I(I0-982)2-0(I3-525)5-I(I0-632)'t'I-4263-2I22-4982700Probabilityof't'occurringbychanceifnorealdifference(P)O-i60-002001Io-oo8NewEntrantDriversv.DriversTransferDriversMean7-4(I74-906)I0-3(I93-33I)8-9(i85-404)26-6(232-799)Standarddeviation24-244I9'41530'77225-938TransfersMean7-3(I74-279)II-4(I18-407)9-2(i86-896)28-6(236-532)Standarddeviation22-II820'4593I62723-052Differencebetweenmeans(drivers-tranisfers)o0I(o-627)-II(-50-76)0-3(-I492)-2-0(-3733)t0-154-1483o-278-o-864Probabilityof't'occurringbychanceifnorealdifference(P)0o-8501-40-780o38TransformedvaluesinbracketsNos.ofobservations:newentrantdrivers,97;transferdrivers,52;newentrantconductors,79.TABLEIIICOMPARISONOFPHYSICALCHARACTER1STICSOFNEWENTRANTDRIVERSANDCONDUCTORSWITHHEIGHTRANGEI73CM.TOI80CM.NewEntrantDriversMeanS.D.NewEntrantConductorsMeanS.D.Differencebetweenmeans(drivers-conductors)tProbabilityof't'occurringbychanceifnorealdifference(P)Height(cm.)SittingStand-ingWeight(lb.)92-8I75-II49*2I16920*o6I6-8I92.7I74-814792-282-35I7-28+O-I+0°3+1I3+0-22+o-6o+0-34o-840o55073Chest(cm.)Inspir-Expir-ationation9I-685-84.4I4.3690g784-05-545.39+0-9+I*8+o-80+I*640o4301o0Waist(cm.)Bi-acro-mialDiam-eter(cm.)76-639.86-46'I4775-839-56-92I30+o-8+053o-58+0-3+0-90SkinfoldThicknesses(mm.)(transformedvaluesinbrackets)Triceps7-3(I74-355)20-346-3(I65-2I8)+I-O(9-137)+I*96o-o6SubscapularIO-I(I9I-854)I6-79-0(I85-428)I8.I3+±I*(6-426)+I.67O0IOSupra-iliacTotalSkinfold(mm.)8-6(I83-520)23-0(232-590)27.1519.326-8(I70211)29-40+±-8(I3-309)+2-090-04i88(223*147)21I55+4-2(9(443)+12+S+2205+1I*30o048.Nt.33.3'Dataon42newentrantdriversand39newentrantconductors(exceptforcholesterolestimationswherenumberswere36and37respectively)SkinfoldstransformedasinAppendixTableII:transformedvaluesshowninbrackets.0-II