Long Term Effects on Risk Factors for Cardiovascular Disease after 12-Months of Aerobic Exercise

22 Pages·2016·0.79 MB·English

RESEARCHARTICLE
Long Term Effects on Risk Factors for
Cardiovascular Disease after 12-Months of
Aerobic Exercise Intervention - A Worksite
RCT among Cleaners
MetteKorshøj1,2*,MarkLidegaard1,PeterKrustrup2,3,MarieBirkJørgensen1,
KarenSøgaard4,AndreasHoltermann1,4
a11111 1 NationalResearchCentrefortheWorkingEnvironment,LersøParkallé105,2100,CopenhagenØ,
Denmark,2 DepartmentofNutrition,ExerciseandSports,CopenhagenCentreforTeamSportandHealth,
UniversityofCopenhagen,NørreAllé51,2200,CopenhagenN,Denmark,3 SportandHealthSciences,
CollegeofLifeandEnvironmentalSciences,St.Luke'sCampus,UniversityofExeter,Exeter,United
Kingdom,4 InstituteofSportsScienceandClinicalBiomechanics,UniversityofSouthernDenmark,
Campusvej55,5230,OdenseM,Denmark
*[email protected]
OPENACCESS
Citation:KorshøjM,LidegaardM,KrustrupP,
Abstract
JørgensenMB,SøgaardK,HoltermannA(2016)
LongTermEffectsonRiskFactorsforCardiovascular
Diseaseafter12-MonthsofAerobicExercise
Intervention-AWorksiteRCTamongCleaners.PLoS
Objectives
ONE11(8):e0158547.doi:10.1371/journal.
pone.0158547 Occupationalgroupsexposedtohighoccupationalphysicalactivityhaveanincreasedrisk
Editor:YoshihiroFukumoto,KurumeUniversity forcardiovasculardisease(CVD).Thismaybeexplainedbythehighrelativeaerobicwork-
SchoolofMedicine,JAPAN load.Enhancedcardiorespiratoryfitnessreducestherelativeaerobicworkload.Thus,the
Received:September28,2015 aimwastoevaluatethe12-monthseffectsofworksiteaerobicexerciseonriskfactorsfor
CVDamongcleaners.
Accepted:June18,2016
Published:August11,2016
Methods
Copyright:©2016Korshøjetal.Thisisanopen
accessarticledistributedunderthetermsofthe Onehundredandsixteencleanersaged18–65yearswererandomizedtoagroupperform-
CreativeCommonsAttributionLicense,whichpermits
ingaerobicexerciseandareferencegroupreceivinglectures.Outcomeswerecollectedat
unrestricteduse,distribution,andreproductioninany
baselineandafter12-months.Arepeatedmeasures2×2multi-adjustedmixed-model
medium,providedtheoriginalauthorandsourceare
credited. designwasappliedtocomparethebetween-groupdifferencesusingintention-to-treat
analysis.
DataAvailabilityStatement:Allrelevantdataare
withinthepaperanditsSupportingInformationfiles.
Funding:ThestudyisexternallyfundedbyThe Results
DanishWorkingEnvironmentResearchFund(journal
Between-groupdifferences(p<0.05)werefoundfavouringtheaerobicexercisegroup:
number20100019624/5).
cardiorespiratoryfitness2.15(SE1.03)mlO /min/kg,aerobicworkload-2.15(SE1.06)%
2
CompetingInterests:Theauthorshavedeclared
HRR,restingHR-5.31(SE1.61)beats/min,highsensitiveC-reactiveprotein-0.65(SE
thatnocompetinginterestsexist.
0.24)μg/ml.Thebloodpressurewasunaltered.Stratifiedanalysesonrelativeaerobicwork-
Abbreviations:ABP,Ambulatorybloodpressure;
loadatbaselinerevealedthatthosewithrelativeaerobicworkloads(cid:1)30%ofHRRseemsto
BMI,Bodymassindex;BP,Bloodpressure;bpm,
Beatsperminute;CVD,Cardiovasculardisease; imposeanotableadverseeffectonrestingandambulatorybloodpressure.
PLOSONE|DOI:10.1371/journal.pone.0158547 August11,2016 1/22
LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
HDL,Highdensitylipoprotein;HR,Heartrate;HR , Conclusion
max
Maximumheartrate;HRR,Heartratereserve;%
Thislong-termworksiteaerobicexerciseinterventionamongcleanersledtoseveralbeneficial
HRR,Percentageofheartratereserve;hsCRP,High
sensitiveC-reactiveprotein;ITT,Intentiontotreat; effects,butalsopotentialadverseeffectsamongthosewithhighrelativeaerobicworkloads.
LDL,Lowdensitylipoprotein;LTPA,Leisuretime
physicalactivity;OPA,Occupationalphysicalactivity; TrialRegistration
RHR,Restingheartrate;SHR,Sleepingheartrate;
VOmax,Maximumoxygenconsumption. Controlled-Trials.comISRCTN86682076
2
Introduction
Individualsexposedtohighoccupationalphysicalactivity(OPA)sufferfromanelevatedinci-
denceofcardiovasculardisease(CVD)[1].CleanersareexposedtohighOPA[2–5]consisting
ofworkingwhilebeingatone’sfeet(standing,walking)[3–5]combinedwithfrequentstatic
workingposturesespeciallyusingtheupperextremities(pushing/pullingthechart/mopping
thefloor)[3,4,6].
AnexplanationforthehighincidenceofCVDamongcleaners[7,8]maybethecombina-
tionofhighOPAandalowcardiorespiratoryfitness,generatingahighrelativeaerobicwork-
load[2–4,9,10].Aphysicalworktaskwillexposeaworkerwithahighcardiorespiratoryfitness
toalowerrelativeaerobicworkloadthanaworkerwithalowcardiorespiratoryfitness
[9,11,12].AscleanersgenerallyhavelowcardiorespiratoryfitnessandhighOPA[5,10,12],
theyareexposedtomoderatetohighaerobicworkloadsthroughoutthemajorityoftheirwork-
ingtime[2–5,10,12].Long-termexposureofmoderatetohighrelativeaerobicworkloadsmay
leadtoincreasedriskofCVD[13,14]duetotheproposedharmfulstressonthearterialendo-
thelia[15].
Therefore,itisrelevanttoaimforaloweredriskforCVDamongcleaners,i.e.byreducing
theaerobicworkload.Areductionoftheaerobicworkloadmaybeachievedbyanenhanced
cardiorespiratoryfitness[9,11,12].Anotherbenefitofanenhancedcardiorespiratoryfitnessis
preservationofthecardiovascularhealth,asseeningeneralpopulations[16,17],butalso
amongworkersexposedtohighOPA[18–21].
Recently,weperformedaworksiteinterventionwithaerobicexerciseamongcleaners.At
4-monthsfollow-uptheanalysisshowedthatthecardiorespiratoryfitnesswasenhanced,and
theaerobicworkloadduringcleaning,restingheartrate(RHR),sleepingheartrate(SHR)[10]
andlevelofinflammationevaluatedbyhighsensitiveC-reactiveprotein(hsCRP)werereduced
[22].AlloftheseresultscontributetoaloweringoftheriskforCVD.However,alsoanincrease
insystolicbloodpressure(BP)wasfoundat4-monthsfollow-up[10,23].Thisfindingmaybea
significantadverseeffectonCVDhealth,butalsoatransientphysiologicaleffect.Therefore,it
isnecessarytoinvestigatethelong-termeffectsfromtheintervention.
ThemainaimofthispaperwasthereforetoevaluatetheeffectsonriskfactorsforCVD
fromacluster-randomizedcontrolledtrialamongcleanerswithworksiteaerobicexerciseafter
12-monthsfollow-up.Wehypothesizedthattheworksiteaerobicexerciseinterventionwould
enhancethecardiorespiratoryfitness,reducetheaerobicworkload,RHR,SHR,andlevelof
inflammationevaluatedbyhsCRP.Additionally,theBPwashypothesisedtobeunaltered.
Methods
Studydesign
Thestudydesignhaspreviouslybeendescribed[24].Briefly,thestudywasconductedasaclus-
ter-randomizedcontrolledtrialwithanaerobicexerciseandareferencegroup.Theintervention
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LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
wasdividedintotwophaseswithdifferentaims.Thefirstinterventionphase,frombaselineto
4-monthsfollow-up,evaluatedtheefficacyoftheinterventiononriskfactorsforCVD
[10,22,23].Thesecondinterventionphasefrom4-monthsto12-monthsfollow-upevaluatedthe
long-termeffects.Outcomesweremeasuredatbaseline,4-monthsafterbaselineand12-months
afterbaseline[24].Thepresentpaperreportstheresultsfrombaselineto12-monthsfollow-up
onriskfactorsforCVD.
ThestudywasapprovedbytheDanishdataprotectionagencyandtheEthicsCommittee
fortheregionalcapitalinDenmark(journalnumberH-2-2011-116)byNovember10th2011
andwasconductedinaccordancewiththeHelsinkideclaration.Thestudywasregisteredas
ISRCTN86682076intheCurrentControlledTrials(http://www.controlled-trials.com/
ISRCTN86682076).Beforetheetichsapprovalwereobtainedthepreparationforthestudy,e.g.
literaturereviewsforgainingknowledgeofthelatestvalidatedmonitorsfordiurnalmeasure-
ments,wereconducted.
Recruitmentofworksitesandstudyparticipants
CleaningcompaniesinthesuburbanareaofCopenhagen,Denmark,wererecruited.Recruit-
menttookplacebydirectlytelephoningoremailingthemanagementofcleaningcompanies
duringtheautumnof2011,andwasterminatedbythelastinformationmeetingatMay15th
2012.Therecruitmentofthecompaniesandparticipantstookplacebeforethestudywas
registredduetoprolongedpilottestingofthediurnalmeasurements.Ifthemanagement
showedaninterestintakingpartintheproject,aprojectmeetingwasarranged.Ifcollabora-
tionwasconfirmed,allemployeeswereinvitedtoaninformationmeeting.Theinformation
meetingstookplaceatthefirstcompanyatNovember22nd2011andNovember25th2011,at
thesecondcompanyatMay15th2012andatthethirdcompanyatJune22nd2012.Atthe
informationmeetingtheemployedcleanersfilledinascreeningquestionnaire,collectingback-
groundinformationsuchasethnicity,smokingstatusandjobseniority.Additionally,the
cleanerswereaskediftheywantedtoparticipateinthestudy.
Atcompanylevel,inclusioncriteriawere:Morethan50employedcleanersandmanage-
ment’spermissionforcleanerstoparticipateintheprojectactivitiesduringpaidworkingtime.
Atparticipantlevel,inclusioncriteriawere:agebetween18and65years,employmentasclean-
ingassistantformorethan20hoursperweek,andsignedinformedconsenttoparticipatein
thestudy.Theonlyexclusioncriterionforparticipatingintheinterventionwaspregnancy.
However,thefollowingconditionsexcludedparticipationinthespecificphysicalcapacitytests:
Congestiveheartfailure,hospitaladmissionformyocardialinfarctionoracutecoronarysyn-
dromewithinthelasttwoyears,anginapectoris,severehypertension((cid:1)160/(cid:1)100mmHg),
seriousorchronicillness,severetrauma,frequentmigraine,andfeveronthedayoftesting.
Allergytoadhesiveplastersexcludedparticipationindiurnalheartrate(HR)measurements.
Randomization
Randomizationwasperformedatcluster-level,aclusterwassetwithinstrata,andstratums
wereformedaccordingtowhichmanagertheparticipantreportedto.Clusterswerebalanced
ongeographicalworklocation,gender,ageandjobseniority.Tominimizeimbalanceacross
severalstrata,theclusterswerepairedaccordingtonumberofparticipants,gender,ageandjob
seniority,withineachstratum.Therandomizationwascarriedoutbyaresearcherblindedto
theidentityoftheparticipants,strataandclusters.Thereliabilityoftherandomizationproce-
durewassupervisedby3researchers.Allpairedclustersassignedtothespecificstratumwere
drawnfromanopaque,tossedbagandwasalternatelyallocatedtoeitherreferenceoraerobic
exercisegroup,dependingoftheflipofacoin.Tailsdecidedallocationofthefirstofthetwo
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LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
drawnpairedclusterstothereferencegroupandheadstotheaerobicexercisegroup.Thesec-
ondofthetwodrawnpairedclusterswasallocatedtotheoppositegrouptothefirst[24].
Intervention
Theauthorsconfirmthatallongoingandrelatedtrialsforthisinterventionareregistrered.All
projectactivitieswerecarriedoutduringpaidworkinghours,atorneartheworksite.Therefer-
encegroupwasofferedlectures,addressinghealthyliving,butnotphysicalactivity,andpartici-
pantswereinvitedtosuggesttopics.Theaerobicexercisegroupwereofferedaerobicexercise
sessionsaimingtobeperformedatanintensityof(cid:1)60%ofmaximaloxygenconsumption
(VO max)[25].Throughamodifiedinterventionmappingapproach[26]theaerobicexercises
2
weretailoredtoeachoftheenrolledcompanies[24].Theinitialaerobicexerciseactivities
offeredwereindoorbiking,runningonatreadmillandaerobics.
Theinterventionhadatotaldurationof12-months,dividedintwointerventionphases.
DuetosummerandChristmasholidaystheactivitieswereofferedforatotalof42weeks.Dur-
ingthefirstinterventionphasethereferencegroupreceived2lecturesof2hours/lecture.The
aerobicexercisegroupreceivedsupervisedaerobicexerciseof2x30minutesperweek,corre-
spondingtoatotalof32sessions(16hours).Duringthesecondphaseoftheintervention,the
referencegroupreceived3lecturesof2hours/lecturewhiletheaerobicexercisegroupreceived
aerobicexerciseof2x30min/week,intotal52sessions(26hours).Thesupervisionoftheaer-
obicexercisegroupwasgraduallydeclined,duringthefirst4-weekperiodsixsessionswere
supervised,duringthesecond4-weekperiodfivesessionsweresupervised,duringthethird
4-weekperiodfoursessionsweresupervised,duringthefourth4-weekperiodtwosessions
weresupervisedandduringthefifthandsixth4-weekperiodonlyonesessionwassupervised
perperiod.Participationintheaerobicexercisegroupwasregisteredonlywhentheinstructor
waspresent.
Datacollection
Allparticipantsweretestedatbaselineandafter4and12-monthsinterventionperiodatthe
worksiteduringpaidworkinghours.ThebaselinemeasurementswereconductedinJanuary
2012atthefirstcompany,inMay2012atthesecondcompanyandinAugust2012atthethird
company,4-monthsfollow-upmeasurementswereconductedinMay/June2012atthefirst
company,inJanuary/February2013atthesecondcompanyandinFebruary2013atthethird
company,12-monthsfollow-upmeasurementswereconductedinJanuary2013atthefirst
company,inJune2013atthesecondcompanyandinSeptember2013atthethierdcompany.
Thetestconsistedofastructuredinterview,physicaltestingofhealth-andcapacity-related
measuresandobjectivediurnalmeasuresofHRandambulatorybloodpressure(ABP)[24].
Participantsgotinstantfeedbackfromthephysicaltestingandwereencouragedtocontacta
physicianiftheirsystolicordiastolicBPexceededrecommendedlevels((cid:1)140or(cid:1)90
mmHg)[27].
Theinterviewassessedgender,ethnicity,countryofbirth,education,occupationalgroup,
employmentstatus,jobseniority,occupationalandleisuretimephysicalactivity[28],smoking,
generalhealth[29],diagnosedillnesses,dailyuseofheart,anti-hypertensive,andcholesterol
reducingmedication.Ethnicitywasclassifiedaswesternornon-westernbasedoncountryof
birth.AllEuropeancountries,Australia,Canada,andUSAwereconsideredwestern.
Physicalexaminationsmeasuredbodyweight(kg)andbodyfat(%)withbio-electric-
impedance-analysistoolTanitaBC418,heightwithSecamodel2131721009,waistcircumfer-
encewithSecamodel201.Thewaistwasdefinedasthenarrowestpointbetweenthelowestrib
andtheiliaccrest[30,31].Bodymassindex(BMI),wascalculatedasbodyweight(kg)divided
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LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
bybodyheightsquared(m2)[30,31].BloodpressurewasmeasuredwithOmronM6Comfort
ontheupperleftarmafterminimum15minutesofsittingrest.Measurementswereconducted
withparticipantswearinglightclothesandnoshoes.Levelofcardiorespiratoryfitnesswasesti-
matedbyasub-maximalsteptest[32]conductedonabenchof30cmheightforfemalesand
35cmformales.Stepfrequencywasincreasedfrom0.2stepspersecondtomaximal0.8steps
persecond,atmaximal6minutesoftestingtime.Thesteptestwasterminatedwhenthepartic-
ipantcouldnolongerkeepthesteppingrhythmorproperlyextendtheknee.
ThediurnalmeasurementsofHRwereperformedwithActiheart(www.camntech.com).
ActiheartisvalidatedformeasurementofHR,HRvariabilityandestimationofenergyexpen-
ditureinthefield[33–35].Theelectrocardiographicrawsignalsaremeasuredwithasensitivity
of0.25mVandHRiscalculatedasthenumberofRpeaksintheQRScomplexperminute.
Beforemeasurement,theActiheartmonitorwasinitialisedbygenderandage,andmounted
withag-ag-clpre-gelledelectrodes(AmbubluesensorVL-00-S/25)atoneofthevalidated
bodypositions[36].Heartratewasmeasuredoverfourdays(mostly2workingand2non-
workingdays).Participantswereinstructedinhowtowearthemonitorandtowritealogof
workinghours,sleepingandwakingtimeandtimeperiodsspentwithoutmonitors.Duringthe
diurnalmeasurements,participantswereaskedtolivetheirnormalevery-daylife.
NumberofstepstakenweremeasuredwiththeActigraphGT3X+(www.theactigraphcorp.
com)andanalyzedinthecustomizedsoftwareActi4[37,38].TheActigraphwasmountedon
theskinwithadhesivetape(3M,Hair-Set,doublesidedadhesivetapeandFixomull,BSNmed-
ical),ontherightthighmedialtotheiliaccrestandthetopofthepatella.TheActigraphwas
orientatedwiththex-axispointingdownwards,y-axishorizontallytotheleftandz-axishori-
zontallyforward.
Ambulatorybloodpressure(ABP)measurementswereperformedwithSpacelabs90217
(www.spacelabshealthcare.com)[39],byoscillometry,mountedonthenon-dominantupper
armwithatubeconnectingthesamplertothecuff.Thesamplerwasmountedwithelastic
strapsaroundthewaist,andthefrequencyofmeasurementswasevery20minutesduringwak-
inghours,andevery40minutesduringsleep[40,41].Theparticipantswereinstructedtokeep
quietandkeepthearmatrestwhilethemeasurementwasproceeding.Ifameasurementfailed,
themonitorautomaticallymeasuredagainafewminuteslater.Participantswereaskedtolive
theirnormalevery-daylifeandtheywereinstructedintakingonandofftheSpacelabswhen
showering.
Theparticipantswereinstructedtowritealogofworkinghours,sleepingandwakingtime
andtimeperiodsspentwithoutmonitors.Thisenabledaclassificationofthe24hoursinto
work/leisure/sleephoursduringdataanalysis.
Bloodsampling
A25-mlnon-fastingbloodsamplewastakenfromthevenabrachialisbytrainedlaboratory
technicians.Thesamplesweretakenduringworkinghours(7a.m.to3p.m.)andnorestric-
tionswereimposedwithregardtofood,caffeine,tobaccoandalcoholconsumptionorexercise
priortothesampling.Thesampleswerestoredat-20°Candanalyzedwithinamaximumof2
yearsforhighdensitylipoprotein(HDL)cholesterol,lowdensitydensitylipoprotein(LDL)
cholesterolandtotalcholesterol(TC),triacylglycerol(TG)andglycatedhemaglobin(HbA ).
1c
Samplesofethylenediaminetetraaceticacid(EDTA)plasmawerestoredat-80°Cuntilanalyzed
forhsCRPandfibrinogenwithinamaximumof2years.
Ahighperformanceliquidchromatography(HPLC)methodwasusedfordeterminationof
HbA .TheHPLCconsistedofaWaters625LCsystemtogetherwithaWatersphotodiode
1c
arraydetectormodel996andaWISP717autosamplerforautomaticinjectionofthesamples.
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LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
Millenniumchromatographysoftwarewasusedtocalculateconcentrations(WatersAssociates
Inc.,Milford,US).AcationexchangecolumnMonoSHR5/5fromPharmaciaBiotechAB,
Uppsala,SwedenwasusedtoseparateHbA fromothercomponentsinthesamples.The
1c
methodforHbA hasbeenevaluatedbyinter-laboratorycomparisonbasedon17patient
1c
samplesandfoundtobelinearintherange4.1‒14.3%oftotalhaemoglobinandwithoutsys-
tematicbias[42].LyphochekDiabetesControl(Calibrator)fromBioRad(Anaheim,CA,US)
forHbA wasusedtomonitorthelong-termstabilityofthemethod.
1c
HDLcholesterol,LDLcholesterolandTCwereanalyzedusingaCobasMIRAPlus.The
determinationofHDLcholesterol,LDLcholesterol,TCandTGwascarriedoutbyABXPentra
assaysfromTriolab(Sollentuna,Sweden).CalculationofLDL/HDLcholesterolratioandLDL/
TCcholesterolratiowascarriedoutbydividingLDLcholesterolbyHDLcholesterolandLDL
cholesterolbyTC.TheanalyticalmethodsformeasuringTCinserumhavebeenevaluatedby
amethodevaluationfunctiondesign[43]toestimatetherandomandsystematiceffects.This
wasbasedonalinearleastsquaresregressionanalysisofthemeasuredconcentrationvsthe
conventionaltrueconcentrationofaseriesofmethodevaluationsamplescontainingcholes-
terol.Thebetween-assayvariationwasestimatedtobe2.7%at5.3mmol/Lcholesterol[44].
CommerciallyavailablecontrolsamplesforHDLcholesterol,LDLcholesterol,TCandTG
wereanalyzedtogetherwiththesamplestoshowequivalencebetweendifferentruns.Westgard
controlchartswereusedtodocumentthattheanalyticalmethodsremainedinanalyticaland
statisticalcontrol,i.e.thattheprecisionandtruenessoftheanalyticalmethodsremainedstable
[45].
FibrinogenwasanalyzedbyturbidimetryonCobasMIRAPlus.Weusedahighsensitive
ELISA(EU59151),purchasedfromIBL,InternationalGMBH,Hamburg,Germany,tomeasure
hsCRP.Thebetween-assayvariationwas5.8%at1.6μg/mlandthelimitofdetectionwas
0.02μg/ml.
SampleSize
Thepowercalculation,performedpriortothestudyshowedthatanexpectedincreasein
cardiorespiratoryfitnessof4%wouldneed52participantsineachofthetwointervention
groupstoshowsignificanceatalevelof0.05.Samplesizecalculationsassumedrecruitmentof
40%oftheeligiblecleanersandadropoutrateof30%duringtheintervention[24].
Analyses
Theprimaryoutcomeinthe12-monthstudyischangeincardiorespiratoryfitness
(mlO (cid:3)min-1(cid:3)kg-1)frombaselineto12-monthfollow-up.Secondaryoutcomesarechanges
2
inrelativeaerobicworkload(%HRR),RHRinbeats-per-minute(bpm),SHR(bpm),resting
systolicanddiastolicBP,24hourambulatoryBP(ABP),andlevelofbiomarkersrelatedto
riskforCVD(e.g.concentrationofhighsensitiveC-reactiveprotein).
OnlyHRmeasurementswithbeaterrorof(cid:4)50%wereincludedtomeetthedataqualitycri-
teriasetbySkotteandcolleagues[37].TheHRreserve(HRR)wascalculatedasthedifference
betweentheestimatedmaximalHR(HR ),estimatedby(208–0.7(cid:5)age)[46],andtheresting
max
HR(RHR)(HRR=HR −RHR)[9].TheRHRwasdefinedasthe10thlowestrecordedHR
max
valueduring24hours[47].Therelativeaerobicworkload(%HRR)wascalculatedasthe
observedHRpercentageoftheHRR((observedHR–RHR)(cid:5)100%/HRR)[9].
ABPmeasurementswereincludedwhenaminimumof25%ofplannedmeasurementswere
complete[39,40].AllmeasuresofABPwerevisuallycheckedforphysiologicaloutliers(systolic
BP<80and>240mmHg,diastolicBP<50and>130mmHg).FortheABPanalysis,the
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LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
HRmeasurementsandestimatedaerobicworkloadswereanalysedin5minutesintervalspre-
cedingeachABPmeasurement.
Statisticalanalysis
StatisticalanalyseswereperformedusingtheIBMSPSSstatisticssoftware(version21)
(Armonk,NY,US)andtheSASstatisticalsoftwareforWindows(version9.3)(Cary,NC,US).
Allanalyseswereperformedaccordingtotheintentiontotreatprinciple(ITT),inwhich
allrandomizedparticipantsareincludedinthestatisticalanalyses[48].Missingvalueswere
notimputedneitherforoutcomenorcovariatevariables[49].Bothwithinandbetween-
groups12-monthchangesofalloutcomeswerecomputedwithstandarderrorsand95%con-
fidenceintervals.Differencesin12-monthchangesofalloutcomeswereanalyzedina
repeated-measures2x2mixedmodelsdesign.Independentcategoricalvariables(fixedfac-
tors)weregroup(aerobicexerciseandreference),measurementtime(baselineand
12-monthsfollow-up),andtheinteractionbetweengroupandmeasurementtime.Partici-
pantswereenteredinthemodelasarandomeffectnestedinclusterstoaccountfortheclus-
ter-basedrandomization.Covariateswerechosenbasedonbaselinedifferencesbetween
groupsontheoreticallyconsideredconfoundersandtheirstatisticalassociationwiththe
groupandmeasurementtime.
Fortheprimaryoutcome,andthesecondaryoutcomesonaerobicworkload,RHR,SHR
andrestingBP,thefollowingcovariates(referencevalueinparenthesis)wereenteredintothe
mixedmodelsinthefollowingincrementalsteps:1)baselinevalueoftherespectiveoutcome,
2)age,gender(male),dailyuseofantihypertensionand/orheartmedication(none),smoking
status(neversmokingand/orcurrentlynon-smoking),andeitherlevelofleisuretimephysical
activity(<2h/weekslightactivity)orbaselinecardiorespiratoryfitness.Theinterventioneffect
estimateswerereportedasbetweengroupmeandifference±standarderror,95%confidence
interval,andp-value.
Forthesecondaryoutcomeson24hourABP,thefollowingcovariateswerestepwise
includedintheanalysis(referencevalueinparenthesis):model1:meanbaselineABPfromthe
respectivetimeperiod;model2:additionallyage,gender(male),dailyuseofhypertensionand
/orheartmedication(none),smoking(neversmokingand/orcurrentlynon-smoking),and
cardiorespiratoryfitnessatbaseline(high).Theestimatedcardiorespiratoryfitnesswascoded
asacategoricalvariablesplitintertiles(low,mediumandhigh),andthoseparticipantswho
didnotconductthecardiorespiratoryfitnesstestconstitutedanextracategory.
ForthesecondaryoutcomesonbiomarkersrelatedtoriskforCVD,thefollowingcovariates
wereincrementallytakenintoaccountintheanalysis(referencevalueinparenthesis):model1:
baselinevalueoftherespectiveoutcome;model2:additionallyage,gender(male),BMI,daily
useofcholesterolandorhormonemedication(none),smokingstatus(neversmokedand/or
currentlynon-smoking),levelofleisuretimephysicalactivity(<2hoursperweekslightactiv-
ity)andalcoholconsumption.
Forthesecondaryoutcomesonbodyweight,fatpercentageandwaistcircumference,the
followingcovariateswereincrementallytakenintoaccountintheanalysis(referencevaluein
parenthesis):model1:baselinevalueoftherespectiveoutcome;model2:additionallyage,gen-
der(male),BMI,smokingstatus(neversmokedand/orcurrentlynon-smoking),levelofleisure
timephysicalactivity(<2hoursperweekslightactivity)andalcoholconsumption.
Secondarily,asensitivityanalysisexcludingparticipantsreportinguseofantihypertension
and/orheartmedicationonadailybasiswasperformedfortheoutcomesoncardiorespiratory
fitness,RHR,SHR,aerobicworkload,restingand24hsystolicanddiastolicbloodpressure,
usingthesamefullyadjustedstatisticalmodel.
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LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
Additionally,sensitivityanalysiswasperformedbyapplyingthesamefullyadjustedstatisti-
calmodelontheoutcomesofhsCRP,fibrinogen,HDL,LDL,TC,TGandHbA1cwiththe
exclusionofparticipantsreportingdailyuseofcholesteroland/orhormonemedication.
Asecondarybetween-groupanalysisstratifiedonbaselinelevelofaerobicworkload(low<30%
HRRorhigh(cid:1)30%HRR)wasconducted.Thecutpointofhighandlowaerobicworkloadwere
basedonpreviousstudies[50,51].
Results
Flowofparticipants
Allthreecontactedcompaniesagreedtoparticipate.Thestudywaspresentedto250cleaningassis-
tantsatthesecompanies.Ofthose,137(45%)consentedtoparticipate(consenters)andwere
invitedtothebaselinemeasurement.Baselinemeasurementswereconductedamong116ofthem
andtheywererandomized,with59assignedtothereferencegroupand57totheaerobicexercise
group.Afterbaselinemeasurements,42(36%)participants(18fromthereferenceand24fromthe
aerobicexercisegroup)droppedoutofthestudyandwerelosttofollow-upat12-months(Fig1).
Theenrolledcleanerscleanedoffices,hospitals,kindergartens,schoolsandsportsfacilities.
Occupationalphysicalactivitiesamongthispopulationofcleanersweredeterminedbythe
workplansandrequirementsmadebytheirmanagers.Theworkplansdescribedwhichrooms
shouldbecleanedduringtheweek,thequalityofcleaningofdifferentsurfacesandareas,empt-
ingofgarbagebinsandwashofcurtains,bedlinenetc.Themajorityoftheoccupationalphysi-
calactivitiestookplacewhilethecleanerwasstandingorwalkingsometimeswhilethebackis
forward/sidewaysbended,sometookplacewhilethecleanerwassquatting,kneeling,sittingor
standingonallfourandsometookplacewithoneorbotharmsliftedaboveshoulderheight.
Thefollowingsignificant(p<0.05)differenceswereseenbetweentheconsentersandnon-
consenters:theconsentershadlowerjobseniority,weremorefrequentlybornoutsideDen-
mark,andhadsufferedmoremusculoskeletaldisordersintheshoulders,arms/wristsandfeet/
ankleswithinthelast30days.Nodifferenceswereseenindiagnosedillnesses,levelofOPA
andLTPA,gender,age,height,weightandjobseniority.
Themainself-reportedreasonsfornon-participationamongnon-consenterswerelackof
time(40%)andnotfindingthestudyrelevant(11%)[10].Oftheconsenters,21werenotran-
domizedbecausetheywithdrewfromthestudybeforethebaselinemeasurementtookplace,or
didnotshowupatthebaselinemeasurement.Thefollowingsignificant(p<0.05)differences
wereseenbetweenthoseconsenterswhowererandomizedandtheconsentersnotbeingran-
domized:theconsentersbeingrandomizedweremorefrequentlybornoutsideDenmark.
Compliance
The36%dropoutat12-monthsfollow-upwasabovetheexpected30%inthepower
calculations.
Adherenceduringtheimplementationperiodwasnotregisteredbecausenotallsessions
weresupervised.Thedropoutat4-monthsfollow-upwaswithintheexpectedinthepowercal-
culations[10].Aftereveryfourthweekofthe4-monthintervention,theHRwasmonitored
duringtheaerobicexercisesessionyieldinganaverageHRRof67%[standarddeviation(SD)
13].Overall,94%oftheplannedsessionswereofferedasplanned.
Baselinecharacteristicsofthestudypopulation
ThebaselinecharacteristicsofthestudypopulationarepresentedinTable1.Participantsran-
domizedtotheinterventionweremainlyimmigrants;86%statedtohaveanotherplaceofbirth
PLOSONE|DOI:10.1371/journal.pone.0158547 August11,2016 8/22
LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
Fig1.Flowoftheparticipants.
doi:10.1371/journal.pone.0158547.g001
thanDenmark,ofthose62%werenon-western.Withintheaerobicexercisegroup,thoselost
tofollow-up(n=24)hadasignificantlyshorterjobseniority(5years),andsignificantlymore
statedtobecurrentsmokers(25%).Therewasatendency(p=0.053)towardsthatmorestated
theirOPAasstrenuous(29%).Withinthereferencegroupthoselosttofollow-up(n=16)had
asignificantlyhigherRHR(5.4bpm).
Interventioneffects
Thebetween-groupsdifferencesin12-monthchangeofprimaryandsecondaryoutcomesare
reportedinTable2forthefully-adjustedmodel2.
PLOSONE|DOI:10.1371/journal.pone.0158547 August11,2016 9/22
LongTermEffectsofAerobicExerciseonCVDRiskamongCleaners
Table1. Descriptionoftherandomizedstudypopulationofcleanersatbaseline(N=116),stratifiedbytheinterventiongroup.
Randomized Aerobic Reference
population exercise (n=59)
(N=116) (n=57)
Mean SD N Mean SD n Mean SD N
Age(years) 45.3 8.6 44.9 9.2 45.7 8.1
Gender(%females) 75.9 88 75.4 43 76.3 45
Height(m) 1.6 0.09 1.6 0.09 1.6 0.08
Bodyweight(kg) 70.7 14.1 69.7 12.7 71.7 15.4
BMI(kg/m2) 26.7 4.5 26.2 4.0 27.1 4.9
Bodyfat(%) 31.6 8.6 31.1 8.3 32.1 8.9
Waistcircumference(cm) 87.6 11.1 86.7 11.0 88.4 11.2
Jobseniority(years) 11.9 7.8 12.3 8.7 11.5 6.8
Currentsmoker(%) 24.1 28 22.8 13 25.4 15
Ethnicity(%nonwestern) 62.1 72 70.2 40 54.2 32
Dailyuseofantihypertensionand/orheartmedication(%) 12.1 14 14.0 8 10.2 6
Dailyuseofcholesteroland/orhormonemedication(%) 13.8 16 12.3 7 15.3 9
Leisuretimephysicalactivity(%<2h/weekslightactivityorlightactivity2–4h/weeks) 72.4 84 78.9 45 66.1 39
Physicalactivityatwork(%havingstanding/walkingworkincludingliftsandstrenuousphysical 60.3 70 63.2 36 57.6 34
work)
Restingsystolicbloodpressure(mmHg) 122.7 21.7 125.2 25.1 120.3 17.5
Restingdiastolicbloodpressure(mmHg) 82.7 12.6 83.7 14.2 81.7 10.8
Cardiorespiratoryfitness(mlO (cid:3)min-1(cid:3)kg-1) 24.9 6.6 24.8 5.8 25.0 7.2
2
Restingheartrate(beat/min) 71.3 14.8 71.7 10.6 70.5 8.8
Sleepingheartrate(beat/min) 49.5 5.8 49.2 6.5 49.7 5.1
Aerobicworkloadduringwork(%ofHRR) 30.9 7.2 30.1 6.7 31.7 7.5
Ambulatorysystolicbloodpressure(mmHg) 120.6 12.7 83 121.8 14.7 41 119.5 10.4 42
Ambulatorydiastolicbloodpressure(mmHg) 77.3 7.7 83 77.3 8.1 41 77.3 7.5 42
hsCRP(μg/ml) 1.47 1.72 1.39 1.30 1.53 2.05
Fibrinogen(g/l) 3.22 0.68 3.24 0.69 3.19 0.67
HDL(mmol/L) 1.53 0.39 1.53 0.36 1.53 0.41
LDL(mmol/L) 3.32 1.00 3.50 0.98 3.16 1.00
TC(mmol/L) 5.66 1.25 5.82 1.25 5.50 1.24
TG(mmol/L) 1.45 0.77 1.48 0.82 1.42 0.71
HbA1c(%) 5.24 0.65 5.29 0.77 5.20 0.51
Note:Mean±standarddeviationsorpercent(n)arereported.[SD=standarddeviation;HRR=heartratereserve].Differencesbetweenaerobicexercise
andreferencegroupswereanalyzedwithstudent’st-testforcontinuousvariables,andwithChi2testforcategoricalvariables.
doi:10.1371/journal.pone.0158547.t001
Thefullyadjustedbetween-groupsdifferenceincardiorespiratoryfitnesschangewas
2.15±1.03mlO /min/kg(95%CI0.11to4.19,p0.04)intheaerobicexercisegrouprelativeto
2
thereferencegroup(Fig2).Thiscorrespondstoan8.6%increaserelativetotheoverallbaseline
meanintherandomizedpopulation.Significantbetween-groupsdifferenceinchangeofRHR
was-5.31±1.61bpm(95%CI-8.50to-2.12,p<0.01)(Fig3).Relativetotheoverallbaseline
meanintherandomizedpopulation,thisdecreasecorrespondsto7.5%.AnunalteredSHRwas
seeninthefully-adjustedbetween-groupsanalysis.Alsoforaerobicworkloadsignificant
between-groupsdifferenceswerefound;-2.15±1.06%HRR(95%CI-4.28to0.03,p<0.05).
Thiscorrespondstoa7.0%decreaserelativetotheoverallbaselinemeanintherandomized
population.ThechangeinrestingsystolicBPshowedatendencytowardsabetween-groups
differencesof3.82±2.38mmHg(95%CI-0.90to8.53,p0.11).RestingdiastolicBPchanges
PLOSONE|DOI:10.1371/journal.pone.0158547 August11,2016 10/22