Working out fatigue: conceptualization, assessment, and theory

Tilburg University

Working out fatigue

Michielsen, H.J.

Publication date: 2002

Document Version

Publisher's PDF, also known as Version of record Link to publication in Tilburg University Research Portal

Citation for published version (APA):

Michielsen, H. J. (2002). Working out fatigue: conceptualization, assessment, and theory. e.b.

General rights

Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain

• You may freely distribute the URL identifying the publication in the public portal

Take down policy

If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Stellingenbehorend bij hetproefschrift: Workingout fatigue:

Conceptualization,assessment,andtheory ShortUnidimensional_{(?) Fatigue}scale(SUF)Guus©

Een vragenlijstop basis van liedteksten

De volgendetienuitspraken gaan over hoe U zich normaal gesprokenvoelt. U kunt per uitspraakkiezen uit5antwoordmogelijkhedenvarierendvanNooittotAltijd,waarbij 1 = Nooit, 2 = Soms, 3=_{Regelmatig, 4 = Vaak. 5}=_Altijd.

Nooit Soms_{Regelmatig Vaak Altijd}

1. Mijn ogen zijnmoe 1 2 3 45

(HetgroteTIKlied -D'n Egelantier)

2. Ik benmoe 1 2 3 45 (Het is laat - Blpf)

3. Ik ben nietziek, alleen maar moe 1 2 3 45 (Ht Amsterdam-_Drukwerk)

4. Ik voel me moe, maarvoldaan 1 2 3 45 (Annabel - Hansde_Booij)

5. Ikben liever lui danmoe 1 2 3 45 (Nergens goed voor - De Dijk)

6. Ikheb zoveel te doen, maar ben zomoe 1 2 3 45

(De koekoek in de klok-_{Herman van Veen)}

7. M'n benen zijn zomoe 1 2 3 45

( 1 Grote lietde-Clouseau)

8. Ik ben moe en dat gaatnooit meer over 1 2 3 45 (Rijden doordenacht-_Blpt-)

9. Van werken word ik veel temoe 1 2 3 45

(Werkenis_ongezond-PaterMoeskroen)

10.Ik ben hetlevennooitmoe 1 2 3 45

(Niemand sterft - Acda &deMunnik)

Items 4 en10moeten_{worden omgescoord. De schaalscore wordt verkregen door alle} itemscoresbijelkaar optetellen.

Working

out fatigue:

Conceptualization,

assessment,

and

theory

•1•

UNIVERSITEIT *311It VAN TILBURG .Tr.

©2002 HelenJ. _{Michielsen,Tilburg}

Druk: Ponsen&_{Looijenbv, Wageningen}

Ontwerp kaft: Marc deHaan, Dianne vanHemert, MichelleHendriks, Marina Latour, Stijn Michielsen

ISBN: 90-6464-168-4

The studies presented in this thesis wereconducted as part oftheNetherlands concerted researchaction on'Fatigue at Work' granted bytheNetherlands

Organization forScientific Research_(NWO)(Grantno:_{580-02-204), and by}

Working

out fatigue:

Conceptualization,

assessment,

and

theory

Proefschrift

ter verkrijging vandegraad van doctor

aan deUniversiteit van_Tilburg,

op gezag vanderector magnificus, prof. dr. F.A. van der Duyn Schouten, in het openbaarteverdedigen tenoverstaan van

een door het_{college voor promoties aangewezen}commissie

in de aula vande Universiteitopvrijdag 13_{september 2002 om 14.15 uur}

door

Helena JohannaMichielsen

Voorwoord

Zoals u kunt zien opdetitelpagina's vandehoofdstukken inditproefschrift, heb ikdit_{proefschriftzeker niet alleen geschreven. Mijnpromotores Guus van}

HeckenTineke Willemsen,en_copromotorJolandadeVries ben ik veel dank verschuldigd. Guus, jij gaat meteenstofkam dooronze teksten heen en zet nog heelwatpuntjes opdeoverbekendei. Bovendien zorgjetijdens onze

'taskforce'-bijeenkomsten vooreenvrolijke nootenrelativeer jedewetenschap opeenprettige manier._{Tineke, je bent}als_{laatste bij}detaskforce gekomen, maar ook_jouwaandeel was _{onmisbaar. Met jou heb ik meniet alleen op} modern seksisme_{gestort, maar ook op}hetmodel van_Tayloren_{Aspinwall. Je} rustenhartelijkheid tijdensonze besprekingenwaardeer ikzeer. Jolanda, jij

bent degene die me namijn afstuderen terug naarTilburghebtgelokt. In het

begin was hetvooral mijn taakdelogistiek vanhetPVA-projectteregelen, daarna heb je er samen met Guusvoor gezorgd dat ik opditproject kon promoveren. Jij hebtme_{geleerd mijn}ideeen korteren_{duidelijkeroppapier te} zetten. Bovendien_corrigeerjetekstenmet_{bovenmenselijke}snelheid.Zonder

jou hadiknooit in zo'n kortetijdkunnen promoveren ! Ookdeandere

co-auteurs, Prof. Dr. Fons vande_{Vijver, Prof.dr. Klaas Sijtsma en}Dr. Marcel Croon,bedank_{ik hartelijk voor}hun _{onontbeerlijke (methodologische) input.}

Onderzoek doenis _{onmogelijk zonderfijnecollega's.} Een_{groot woord}

van dank gaat uit naar alle (aio-)collega's vanhet departement Psychologie en Gezondheid en van andere departementen.Mijn overburenMichelle

(Goedemorgen !)en_{Annelies (Okkie!),}verre _{overbuur Dianne (Let's keep} returning !),enexterne_{collega Anouke (Ik hebje}helaas_{niet kunnen inhalen !)}

wil ik_{bedanken voor de vele gesprekken die we hebben gevoerd over de}

wetenschap en hetleven. Ik vind hethartverwarmend dat_{ik altijdbijjullie mag}

binnenvallen, deur openofdicht! _SegerenMichelle _{(dezel fde), bedankt voor}

het verzinnen vandetitel vanhetproefschrift!

Mijn werk opde Universiteitvan_{Tilburg isook inspirerend door de} studenten aan wieik_{onderwijs geef en}de_{samenwerking met}hetAudioVisueel Centrum (Chris Nieuwenhoven en HenkvanOpstal)en _{ICT-deskundige drs.}

HenriVermijstenbehoeve vandeimplementatie vanICT-toepassingen in de

cursus.Deafwisselingtussenonderzoek en is nietalleenmotiverend, het

ICT-verhaalverhoogt ookzekermijneigenwaarde op technischgebied! Over techniek_gesproken,demedewerkers van SPITS verdienen alle lof. Julliesnelle en goedehulphebben kleine paniekaanvallen tijdenshet layouten van het

manuscript voorkomen.

Mensen die bereid waren onze vragenlijsten inte vullen zijn per

definitie_{noodzakelijkgeweest voor}ditonderzoek. Iedereen van het

telefonischbenaderdzijn, heeft uren vanzijnvrije tijdheeft aan het beantwoorden vande_{honderden vragen: bedankt daarvoor!}

Een_{bijzonder woord van dank}verdienen _mijnvrienden ende mensen van_mijn moeders groep, dienietalleen_{zorgden voor de velegezellige uren,}

maarookbereid wareneenluisterend oortebiedenwanneermijn privt-leven

dynamisch was. Ik stel dat heel erg op prijs. Bovendien wil ikmijnparanimfen,

EstherenChristina, inhet_{zonnetje zetten.}Jullie levenswijsheiden_praktische adviezen_{houden mij ophet goede pad.}Julliekunnenluisterenzondermeteen te oordelenen levenendenken mee metelkenieuwe stap die ik zet. Ik hoop.

dat jullie mijn heletoekomst mijn raadsvrouwenwillen zijn!

Zonderdesteun,liefdeenbelangstelling van mijnvaderenStijn te kort te willen doen, wil ikalslaatste mijn moedernoemen. Mam, je hebt nu toch het

laatstewoord, wantzoalsalleen_jij verwachtte, ben ikhetonderzoek ingegaan.

Aan_{joudraag ik}dit_{proefschriftop,} omdat je me allelessen hebtgeleerd, die ik nodig heb voor het door jouzo_{gewaardeerde 'echte}leven'. Ik hoop dat ik de

afgelopenjaren er weer wat meesterpunten bij hebgekregen. Ik weet dat je

niets omtitels gaf. maar in mijn gedachten zitjevrijdag 13 september trots te stralen opde eersterij. Bedanktvooralles!

Contents

Chapter 1

Introduction 1

Chapter 2

Examination ofthe_{dimensionality} offatigue:

The construction ofthe_{Fatigue Assessment}Scale (FAS) 13

Chapter 3

Psychometricqualities ofabriefself-ratedfatiguemeasure:

The Fatigue AssessmentScale (FAS) 33

Chapter 4

In searchofpersonalityandtemperamentpredictorsoffatigue:

A_prospectivestudy 51

Chapter 5

Whichconstructs can_{predict fatigue?}

A study into thedeterminantsoffatigue 71

Chapter 6

Predictors offatigueandemotionalexhaustion:

Amodel-based prospective study 97

Chapter 7

Summary, conclusions,anddiscussion 121

Appendix 133

Samenvatting 135

Acknowledgements 141

Chapter 1

2 CHAPTER I

Introduction

Recently, fatiguehasbecome ahottopic,primarily due totherecognition of

the highprevalenceoffatigue inthegeneralpopulation (Loge, Ekeberg. &

Kaasa, 1998) and in primarycare (Bates et al., 1993; Bensing,Hulsman, & Schreurs, 1996;Fuhrer, 1994, Lewis &_Wessely, 1992).However, in the scientific community. thereisstillno general agreement about thedefinition of

fatigue. Furthermore, studies arescarcein whichanelaboratedtheoretical

framework has been used toexplore underlyingfactors

of

fatigue.

The present researchaddresses theconceptualization offatigue, especiallyitsdimensionality. Secondly, theproject deals withtheconstruction

and_{psychometric evaluation of a}new,unidimensional fatiguescale.

Furthermore, the

utility of

atransactional stress-coping-fatigue model, developedbyTaylorand_{Aspinwall (1996),} istested.This model is_employed toidentifyfactors which predict fatigue.

This chapterdeals withthehistoryandassessment of thefatigue

concept,andrelevantmodels that havebeenproposed thus far. Next, the theoreticalframework andthedesign ofthe presentstudyaredescribed. This

chapter ends with abrief overview ofthe_{remaining chapters of this} dissertation.

Chronic fatigue

In everyday life,fatigue is anormal phenomenon, thatis characterized by task-specificity. It canbe reversed in theshort term byrest,switchingtasks, or by usingparticularstrategies,forinstance, working ataslower pace. In the psychological literature, this type of fatigue is referred toasacute _fatigue

(Meijman &Schaufeli, 1996). Although fatigueis_{common, one}must beware

of considering it to be atrivialcomplaint (Lewis

&

Wessely, 1992). The

chronic form of fatigue is independent of a certain task and cannot be reduced by rest orsleep(Meijman& Schaufeli, 1996).

Chronic fatigue isa_{symptom ofmanychronic physical}diseases, like

multiplesclerosis, cancer,Parkinson'sdisease, rheumatoid arthritis, and

psychiatricdisorders such as_{depression(Lewis} &_{Wessely, 1992). In the}

Chronic_FatigueSyndrome(CFS), fatigue is thecoresymptom.Inaddition, fatigue can also play a rolein temporaryphysical conditions such aspregnancy andinfections. Finally. the useofmedication ormedical treatments, such as chemotherapy,canevoke_feelingsof_{fatigue. Thus, profound fatigue is a}

common complaint in_{medical practice(e.g.. Bensing et al.. 1996). Along with} headache,fatigue is themostfrequentlyreported symptom in general practice (e.g., Foets& Sixma, 1991).Chronic fatigue is not onlya_{frequentcomplaint in}

INTRODUCTION 3

disabilitycomparable tothatfound inindividuals suffering fromachronic illness_{(Kroenke, Wood, Mangelsdorff, Meier,}& Powell, 1988).

Fatigue does not only leadtoindividualcosts. Severefatigue during a relatively longperiod can also lead to sickleave andwork disability. For example, in theNetherlandsover one-third oftherecipients ofworkdisability benefitis_categorizedas_{occupationally disabled}on _{mental grounds}(Houtman,

1997). Themajority oftheseindividuals suffers from chronic_jobstress and

burnout. The mostcharacteristic componentofburnout (Schaufeli & Van Dierendonck, 1994) isemotionalexhaustion, a_{fatigue-related concept. A} possible reason fortheincreasingattentionforfatiguecould bethegrowing

awareness of thehigh prevalenceoffatigue and itspotential detrimental effect

on_{individuals' well-being}(Smets et al., 1998).Therefore, in 1996, a

multidisciplinary, six-yearnational research programnamed 'Fatigue at Work' was initiated byThe Netherlands Organization forScientific Research (NWO). It includes medicaland_{psychological} research on acuteand_{prolonged fatigue} among employees. Themajor goals ofthe program are toimprovethe scientific knowledge ofmental fatigue and to develop research-based toolswhich can be

usedin_{occupationalhealth settings. In the}program, mental fatigue has been defined interms ofchanges in thepsychophysiological controlmechanism that regulates taskbehaviour.These changes areconceived of as theresult of preliminarymental and/or physical efforts, whichhavebecome burdensome to suchan extent thatindividuals are nolonger able to meetjobdemands

regarding theirmental functioningadequately.Frequently, individuals are only

able to meetthesedemands at the cost

of

increasingmental effort and the surmounting ofmental resistance(Meijman& Schaufeli, 1996).Thus, mental

fatigue reflects lacking capability as wellas motivation.

Mental fatigue hasbeen studied in fourresearch areaswithintheFatigue at_{Work program.}Thefirstline,focussing on _{'acute fatigue',}hasincluded

projects on shift work,actionregulation, andthepsychobiologyoffatigue. Secondly.chronic fatigue hasbeen studied in projectson personality and

temperament, spill-over, effort-reward imbalance, social comparison, and emotional contagion. In thethird area.theepidemiologyoffatigue has been the focusof_{study. Finally, the}line _{'occupational medicine}and_{fatigue at work',}

which is_particularlyrelevant_{for practitioners,} hasdealt withthe_development

ofdiagnostic protocols,screening instruments, andtheevaluation oftreatment andrehabilitationprograms.

At Tilburg University, thefocus has been on the second research area,

more specificallyon spill-overeffects, and themediatingand _{moderating roles}

of personalityand temperament in therelationshipbetweenworkstress and mentalfatigue. Recently, DeVries and Van Heck (2000) stated inareview

articleon _personalityandemotionalexhaustion that.althoughpersonality is

4 CHAPTER 1

Schaubroeck. 1991). not much research has been done to studytheassociations between personalityandfatigue. In thisdissertation. attentionisgiven to this relationship. In this context, thedimensionalityandpredictors

of

chronic fatigue are studied. Inaddition, thedevelopmentandevaluation of a new fatigue measure aredescribed.

Fatigue, afuzzy concept

Although fatigue is now an _intensively studied construct. no_{general agreement} exists on its definition. In the 19'hcentury,fatiguewasconsidereda strictly

physicalphenomenon. Based on_{experiments concerning physical fatigue,} Mosso (1903)concluded that nexttophysical. alsomental aspectsinfluenced

task performance. He wasthe firsttodescribea unitary viewoffatigue,

combining physicaland_{mental aspects. Unfortunately,} he_{considered fatigue as} arather vague sensationoftiredness. Attemptsto measure mental fatigue as a reduction

of

mental energyfailed andthis. amongotherthings, ledMuscio

(1921)toadvise researchers todropfatigue as ameasurable phenomenon.

Views such astheseprecluded thedevelopment ofanadequatephenomenology

of

the_feelingoffatigueand_placed

it

_{beyond measurement. It wasonly after}

World War 11, thatBartleyand_{Chute (1947)}suggested a new method to assess fatigue. Intheir opinion, fatigue could notbestudied_{directly. However, the} various phenomena towhich fatigue wasrelatedcould serveas standards

instead ofasinglequantitative unit. In contrast, clinicianswere encouraged to

pay attention tothedirectmeasurementoffatigue,because an increasing numberofindividuals_{reportedunexplained feelings}offatigue(Jaspers, 1963).

Grandjean (1979) described the nature

of

fatigue asa statemarked by

reducedefficiency andageneralunwillingness to work. In _1994, Brown definedfatigue as adisinclination tocontinue taskperformance.It involved an impairmentofhuman _{efficiency. when work continued afterpeople became} aware oftheir fatiguedstate. Despitethese andother attempts. todaystill no

general agreement exists on thedefinition offatigue. For amore precise

conceptualizationoffatigue. it ishelpful to notethatfatigue, theoretically, can

be divided into_physical and mental_categories.

Mental fatigueisbelieved to bea_gradualandcumulative _{process. It is} thought tobeassociated with adisinclination foranyeffort.reducedefficiency

and alertness. as well as_{impaired mentalperformance (Grandjean. 1979).}

Mental fatigue isafunctional state, which isa_{continuum with, at the one end,} sleep, and, atthe_{contrast pole,}a relaxed, restful condition. Both_{endpoints are}

likelytoreduceattentionand alertness. Physical fatigue, ontheother hand, is characterized by reducedmuscular powerand movement. Anumber of

researchersfound support forthedistinction mental-physical fatigue,basing

INTRODUCTION 5

(Chalder et al., 1993: David et al., 1990; Ray, Weir, Philips, &Cullen, 1992;

Smets, Garssen,Bonke, & De Haes, 1995,Vertommen&_{Leyssen, 1988).}

Some have proposed an even morefine-grained classification and have distinguished up tofivefacets

of

fatigue intheirmeasures. For instance, Ahsberg (2000)initiallydivided perceived fatigue after work in lackofenergy,

physical exertion, physical discomfort, lackofmotivation, and sleepiness.

However, shedemonstrated that, whiledistinguishingthese fivedimensions. lackof_{energy appeared to be} a_{general latent}factor. Vercoulen, Alberts, and

Bleijenberg (1999)stated that_{fatigue consists of}four_aspects: subjective feelingsoffatigue, reduction inconcentration, lackofmotivation, and_physical

activitylevel.Others (e.g., Desmond& Hancock,2001;Gaillard, 1996; Studts,

De Leeuw,

&

Carlson, 2001)claimedthatfatigueshouldbetreated as a

unidimensional concept, due tocomplex interactionsbetweenphysical and

mental elements in task andjobdemands and consequences

of

effort_(Gaillard,

1996). Furthermore, inarecent_{explorative study of}the structureof_fatigue,

Studts et al. (2001) failed tofind support for thedistinctionofcognitive, emotional,somatic, and_{general aspects} offatigue. Instead, theyfounda clear one-factor solution. This confusion about the_{dimensionality}offatigue makes

clear that systematic research into thedimensionsoffatigueis still necessary.

Due to a lack

of

agreement about the definition, fatigueis measured in

different_{ways.Objective} measures suchasreaction timeor numberoferrors

(Akerstedt, 1990), and_subjectivemethods suchas_{diaries (e.g.,} Vercoulen et al., 1996), interviews (e.g., Meesters& Appels. 1996),and questionnaires (e.g., Chalder et al., 1993) havebeen_{employed. In large-scale studies, such as the} ones described in this dissertation. the use

of

questionnaires is avery common

procedure.Untilthe nineties(Berrios, 1990), scalesof_{fatigue were}

unidimensional. Thecomplex nature of CFS isprobablythereason for the

rising need formorefine-grained, multidimensional measures. However, many fatigue questionnaires in theworkfieldwere developed on an ad hoc basis (De

Vries & VanHeck. submitted). Consequently,the first aim ofthisdissertation

was to focus onthedimensionality

of

fatigue. More specifically, the

dimensionality of four frequentlyusedfatiguequestionnaireswasexamined and anew measure, the Fatigue AssessmentScale (FAS)was developed on the

basis ofasemantical analysisofthesefour_{questionnaires.} Predictors offatigue

Although, ormaybe because,fatigue is such a_{common phenomenon, so far not} much systematic theorizingaboutfatiguehastaken place. However, some

authors (e.g., Bartley&Chute, 1947: Smets et al.. 1995; Vercoulen et al.,

CFS-6 CHAFTER 1

patients. Intheirmodel offatigue,attribution

of

complaints toa somaticcause

results in lowlevels

of

physicalactivity, which in turninfluencesthe severity of fatigue. Bothsenseofcontrol_{over symptoms}and_focusingon_bodily sensations_{affect fatigue directly. As} analternative,a _{biospychosocial} approach,whichtakes intoaccountthecombined effectsofphysical,

psychological,andbehavioral factors, has been proposed as the most suitable wayofexamining fatigue(e.g., David et al., 1990; Lewis&_{Wessely, 1992;}

Ware, 1993). The view thatfatigueis related to varioustypesofextreme

stimulation involving low as well as high physical and/or

information-processing demands (DeRijk, Schreurs,

&

Bensing, 1999) and thebelief that fatigue links with symptomperceptionmodels (e.g., Pennebaker, 1982) are also promisingstepstowardsfurther theorizing.

The second part of thisdissertationaddressesthedirect relationship

betweenpersonality, temperament, and the TypeAbehaviorpattern, on the one hand,and_{fatigue, on} theother hand. In _addition,a_{central role in this part of}

the dissertation isplayed bythe model developed byTaylorandAspinwall (1996). Thismodel describesmediatingand_{moderatingprocesses of}

psychosocial outcomes, suchasfatigue. In this dissertation, themediating part

ofthe modelwas tested. As depicted inFigure 6.1, thismodelincludes external resources,personality, stressors,appraisal. socialsupport,andcoping. Taylor

and Aspinwall(1996)defineexternal resourcesasresourceswhich comprise

aspects of theindividual'senvironment,shaping the demandsandaffordances

of

thesituation. Inadditiontomundaneexternalresources, such as time and

money,adiverse setofenvironmental conditions, ranging fromthe_physical

environmenttosocial roles andother_{aspects of}theindividual's_{place in social}

aggregates,areviewedasexternal resources.External_{resources may}determine the kinds

of

stressorstowhich oneisexposed, but mayalso influenceappraisal and coping.Similarly, personal resources mayaffectexposure to and

disengagementfrom situations, as well as_{appraisal and coping.} In addition,

personal resourcesmayinfluencetheavailability, mobilization, and

maintenanceofsocial support.Social support, in turn, mayaffect coping indirectly throughappraisal processes anddirectlythroughtheprovision of informationandfunctional assistance.Finally.the modelsuggests that the

effectsof_personaland_{external resources, stressor, appraisal,}andsocial

supporton_{psychosocial outcomes} aremediated _{substantially by ways of}

coping withstress.

The debate aboutthe_{conceptualization}of_{fatigue and}the_incomplete

knowledgeaboutthepredictors

of

fatigue have led tothefollowingresearch questions:

INTRODUCTION 7

(ii) Which working individualsreport ahigh levelofprofound fatigue?

Design of the present study

Twosamplesparticipated in this study:a_groupof working_{people and a} general sample. The firstsampleconsisted of two subsamples.Participants of

thisfirstsubsample (n = 765 atthefirstmeasurement: n = 351 two yearslater)

lived equallyspread overthe Dutchregions. Theywererecruited through random_{digitdialing.}

All

selected_{respondents had a paid job for}at least 20

hours per week. Theywere asked in thefirsttestbooklettocompleteanumber

of questionnaires as part ofa _{longitudinalstudy,consisting of five}

measurement_{points in two} years.A smallergroup of 111 _{respondents, who}

worked atanoccupationalhealth service, formedthe second subsample. The lattersubsample filled outonlyparts of the testbattery thatthefirstsubsample

was given. As aconsequence, this subsample wasonly combined withthe first

subsample in the studyreported inchapter 2. Thefirst and second subsample of theworking participants didnotdiffer onanyfatigue variableused, except on

emotional exhaustion. Inthetotal working sample, 452 men and412women participated at baseline(total response =48%). Threehundredand_twenty-five

individuals returnedacompletedtestbooklet at all measurementpoints: 173

men and 150women.Genderwasunknown fortwo respondents. Thissample

couldbe_{considered representative, as}no _{significant differences}werefound with regardto personality,temperament, andfatiguebetween individuals who only participated atthe firstmeasurementpointandpersons who were also

involved in the last measurementpoint,two years later. Lowereducated people were somewhat underrepresented andhighlyeducated personsslightly

overrepresented in theworking sample. However, this is not uncommon for a survey study (Saris, 1988).With respect to gender, maritalstatus. and age, the sample isrepresentative forthe Dutch working population (CBS, 1999). The data collectionwas_{performed with support from NWO,}theNetherlands

Organization forScientificResearch, withinthe framework ofthe nationwide project 'Fatigue atWork' (Grant: 580-02-204) and from WORC,the research

institute ofthe_FacultyofSocial Sciences_{of Tilburg} University.

Participants inthesecond sample (n = 1,893) completeda

computer-administered_{questionnaire.}CentERdata, aninstitute_{of Tilburg}University specialized indatacollection viatheinternet, supplied the data ofthis sample.

This group was studiedinorder to testthepsychometric qualities ofthe Fatigue Assessment Scale, the questionnaire developed inthis study.

All

respondents

were members ofaninternet-based telepanel.Every week aquestionnaire from

8 CHAPTER 1

consisted of 1,128 men and 765women. _{Fifty-seven percent of this sample had} a paid job.Thissampleisincluded in _{chapter 2.}

Overview of thisdissertation

Dimensionality offatigue

In chapter 2, theresults oftwo studiesarepresented. The goal

of

Study I Was to examinethedimensionality of four frequentlyusedfatiguequestionnaires. The aims

of

Study II weretoconstruct a newfatigue instrument, the FAS, and to explore itspsychometric qualities. In this chapter, the extendedworking sample andthe CentERdata samples were used. In the otherchapters. only the data of

the workingsample were analyzed.

In chapter 3.the_{psychometric qualities of the FAS} arefurtherdescribed. The scores on this scalewerecompared with (i) the four fatiguescales on

which the FAS is based,measured twoyearsafterthestart ofthestudy, and (ii)

adepression questionnaire (measuredtwoyearslater) andanemotional stability scale,measuredat_{baseline. In this way, internalconsistency.} convergent validity, and_{divergent validity}were studied. Gender bias was tested in an_{exploratory way.}

Predictors offatigue

Chapter 4 is also based on two measurementpoints. Aim ofthisstudy was to examinewhethertemperament,personality. and a TypeAbehaviorpattern

could predict chronicfatigue. Analyseswere _{performed with}andwithout taking intoaccountfatigueas measuredatbaseline. The data ofthetotal sample as well as data for men and women separately wereexplored.

In chapter 5, the model of Taylorand_{Aspinwall (1996)}is addressed. The main objective ofthis study was to testthis model. Dataconcerning

demographic variables, personalityandtemperament,work pressure and

workload, _{perceived social support, perceived}stress, coping,andemotional

exhaustion, all measured atbaseline, wereincluded. Emotional exhaustion was thedependent variable inthe model. In chapter 6. the model was tested in a

similarway. However, insteadofusingonly emotionalexhaustion as the outcome variable, the FAS, a more generalfatigue measure. was also employed. _{Moreover, fatigue} measured two yearslaterwas included in the

analyses in order to shedsomelightonwhichfactorscanpredict fatigue over time. In this part ofthe study,aprospective design wasapplied.

Finally.chapter7 _provides a _{summary and}a_{general discussion.}It offers

INTRODUCTION 9

References

Ahsberg,E. (2000). Dimensions

of

fatigue indifferent working populations. Scandinavian Journal of Psychology, 41.131-241.

Akerstedt. T. (1990). Psychologicalandpsychophysiological effectsofshift work. Scandinavian Journal of Work, En\,ironment & Health, 16.67-73.

Bartley. S. H.. & Chute, E. (1947). Fatigue and impair,nent in man. New York:

McGraw-Hill.

Bates, D. W., Schmitt. W., Buchwald, D., Ware, N. C.. Lee,J.,Thoyer, E., Kornish, R. J.,& Koniaroff. A. L. (1993). Prevalenceoffatigue and

chronic fatigue syndrome in aprimary c·are practice. Archives of Internal

Medicine, 153, 193-197.

Bensing.J., Hulsman, R..& Schreurs, K. (1996).Vermoeidheid: Eenchronisch probleem [Fatigue: A chronic problem]. Medisch Contact, 51.123-124. Berrios, G. E. _{(1990). Feelings}of_fatigueand_{psychopathology: Aconceptual}

history. Comprehensive Psychiatry, 31,140-151.

Brown, I. D. ( 1994). Driverfatigue. Human Factors, 36,298-314.

CBS (1999). De_{leef'situatie van de Nederlandse bevolking 1997. Deel 1:} Ge=ondheid en arbeid [ Life circumstances of the Dutch population

1997. Volume 1 : Health and work J. Voorburg/Heerlen. The

Netherlands: CBS.

Chalder.T.. Berelowitz,G.,Pawlikowska,T., Watts, L.,Wessely, S.,_Wright.

D.. & Wallace, E. P. (1993). Development of a fatigue scale._{Journal of}

Psychosomatic Research, 37.147-\53.

David,A., Pelosi,A.,McDonald, E., Stephens, D., Ledger, D.,Rathbone, R., &

Mann. A. (1990).Tired, weak, or in need ofrest: _{Fatigue among general} practice attenders. British Medical Journal. 30.1199-1202.

De Rijk, A.E.. Schreurs, K. M. G., & Bensing, J. M. (1999). Whatisbehind

'I'm so tired'?Fatigue experiencesandtheir relations tothequality and quantity of external stimulation.Journal of Psychosomatic Reseat·ch,

47.509-523.

De Vries, J., & Van Heck, G. L.(2000). Persoonlijkheiden emotionele uitputting. Eenoverzicht vande _{literatuur [Personality}andemotional exhaustion. A review of the literaturel. Gedrag &Gezondheid,

28,90-105.

De Vries, J., & Van Heck, G. L._{(submitted). Fatigue and work: The role of}

personality.

Desmond. P. A., & Hancock, P. A. (2001). Active and_{passive fatigue}states. In

P. A. Hancock & P. A. Desmond (Eds.). Stress, workload. and fatigue

(pp. 465). Mahwah. NJ:Erlbaum.

10 CHAPTER 1

gezondheidsgedrag in de praktijkpopulatie [A national study concerning diseases and activities in the general practitioner-practice. Report on health and health behavior in the GP-practice population

j.

Utrecht, The

Netherlands: Nivel.

Fuhrer, R. (1994).Epiddmiologie de lafatigueen _{mddecine gandrale}

[Epidemiology of fatigue in primarycare]. L'Encdphale, 20, 603-609.

Gaillard, A. W. K. (1996).Stress: Produktiviteit engezondheid [Stress:

Productivityandhealth].Amsterdam.The Netherlands: _Uitgeverij

Nieuwezijds.

Ganster, D. C., &Schaubroeck, J. ( 1991). Role stressandworkerhealth: An

extension of the plasticity hypothesis ofself-esteem._{Journal of Social}

BehaWor and Personality (special issue), 6. 349-360.

Grandjean, E. (1979). Fatigue inindustry. British Journal of Industrial

Medicine, 36, 175-186.

Houtman, I. L. D. (Ed.).(1997).Trends iii arbeid en gezondheid 1996 [Trends

in workand_{health 1996].}Amsterdam. TheNetherlands: NIA-TNO.

Jaspers, K. (1963).General psychopathology (Hoenig, J., Hamilton, M.W., Trans.). Manchester.United Kingdom: ManchesterUniversityPress.

Kroenke, K., Wood, D. R., Mangelsdorff, A. D., Meier, N. J.,& Powell, J. B.

(1988). Chronic fatiguein primarycare: Prevalence, patient characteristics, and outcome.Journal of the American Medical

Association, 260.929-934.

Lewis, G., &Wessely, S. (1992). The epidemiologyoffatigue: Morequestions

than answers. Joitmal of Epidemiology and Community Health,

46,92-97.

Loge, J. H.,Ekeberg, 0.,

&

Kaasa, S. (1998). Fatigue inthe general Norwegian population: Normative data andassociations.Journal of Psychosomatic Research, 45,53-65.

Meesters. C.,

&

Appels. A. (1996). Aninterviewtomeasurevital exhaustion. I.

Developmentand_{comparison with} the _{Maastricht Questionnaire.}

Psychology and Health, 11.557-571.

Meijman, T. F., &Schaufeli, W. (1996). Psychischevermoeidheiden arbeid.

Ontwikkelingen inde_{A&0-psychologie[Mental fatigue and work.}

Developments in work and organizational psychology]. De Psycholoog, 31,236-241.

Mosso, A.(1903). La fatigue: Intellectuel etphysique _{IFatigue: Intellectual and}

physicall Paris, France: Alcan.

Muscio, B. (1921). Is a Fatigue Testpossible?British Journal of Psychology,

12,31-46.

INTRODUCTION 11

Ray. C., Weir, W. R.C., Philips, S.,&Cullen, S. (1992). Development of a

measureof_symptomsin_{chronic fatigue syndrome: The}Profile of

Fatigue-Related Symptoms(PFRS). Psychology and Health, 7, 27-43.

Saris, W. E. (Ed.). (1988).Variation in response behaviour. A source of

measurementerrorin_survey research.Amsterdam, The Netherlands: SociometricResearchFoundation.

Schaufeli, W., & VanDierendonck, D.(1994). Burnout,een_{begrip gemeten.} De Nederlandse versie vandeMaslach_{Burnout Inventory}(MBI-NL)

[Burnout,the measurement ofa_{concept. The}Dutchversion of the

Maslach Burnout Inventory(MBI-NL)].Gedrag & Gezondheid, 22,

153-172.

Smets, E. M.A.,Garssen, B.,Bonke, B., & De Haes, J. C. J. M. (1995). The Multidimensional Fatigue Inventory(MFI).Psychometric qualities of an

instrument to assess fatigue. Journal of Psychosomatic Research, 39,

315-325.

Smets, E. M.A., Visser, M. R. M..Garssen, B.,Frijda, N. H., Oosterveld, P., &

De Haes, J. C. J. M. (1998). Understandingthelevel of_{fatigue in}cancer

patients undergoing radiotherapy, a review of the literature.Journal of

Psychosomatic Research, 45, 277-293.

Studts, J. L., DeLeeuw, R., &Carlson, C. R.(2001). Symptom structure of fatigue: A multidimensional or unidimensional constructforbehavioral

medicine?_{Psychosomatic Medicine, 63,130.}

Taylor, S. E..&Aspinwall, L. G. (1996). Mediating and_moderatingprocesses

in psychosocial stress. In H. B. Kaplan (Ed.), Psychosocial stress.

Perspectives on structures, theory, life-course andmethods(pp.

71-110). San Diego. CA: AcademicPress.

Vercoulen, J. H. M.M., Alberts, M.,

&

Bleijenberg, G. (1999). DeChecklist Individual _Strength.Gedragstherapie, 32, 131-136.

Vercoulen, J. H. M. M., Swanink, C. M. A.,Galama, J. M. D.,Fennis, J. F. M..

Jongen, P. J. H.,Hommes, 0. R., Van der Meer, J. W. M., &

Bleijenberg, G. (1998).The persistenceoffatiguein chronic fatigue syndrome and multiple sclerosis: Development of amodel.Journal of

Psychosomatic Research, 45,507-517.

Vertommen. H.,&Leyssen, J. (1988). Vermoeidheid: Van onhanteerbaar symptoom tot diagnostisch waardevollegemoedstoestand [Fatigue:

Froman unmanageable symptom toa_{diagnostic valuable state of mind].}

Tijdschrift voor de Klinische Psychologie, 18,35-59.

Chapter 2

Examination of

the

_{dimensionality}

of

_fatigue:

The construction of

_{the Fatigue}

Assessment

_{Scale (FAS)'}

' Michielsen. H.J.,DeVries, J.. Van Heck. G.L., Van de_{Vijver, A.J.R., &} Sijtsma, K. (submitted). Examination ofthe_{dimensionality}of_{fatigue: The}

14 CHAPTER 2

Introduction

Thischapter reports two studies. The goal ofStudy I wastoexamine the

dimensionalityofexisting fatiguescales. The aimsof_{Study II were to}

construct a new self-report fatigue instrument andtoexamine itspsychometric

qualities. InStudyI, respondents. who worked atleast 20_{hours per week,} completed four fatiguequestionnaires. The 10-itemFatigue Assessment Scale

(FAS)was constructed_{in Study II} andadministered to a_{general sample.} Profound_{fatigue is} acommon complaint in medical practice (e.g.,

Bensing, Hulsman, & Schreurs, 1996). It isa_{symptom ofmany}chronic physicaldiseases, like_multiplesclerosis. cancer.Parkinson'sdisease,

rheumatoid arthritis, and_psychiatricdisorders suchas_{depression(Lewis &}

Wessely, 1992). Insomediseases, fatigue is even thecore symptom as. for example, in theChronicFatigueSyndrome(CFS). Moreover, fatigue can also play a role in temporary physical conditions suchas_pregnancyandinfections. Finally,apartfrombeing anindicatorofdisease,fatigue may alsoresult from

the useofmedicationor medicaltreatments. suchaschemotherapy.

Although fatigue.alongwithheadache. is the mostfrequentlyreported

symptom ingeneralpractice (e.g., Foets& Sixma, 1991), notmuch systematic

theorizinghastaken place yet. However,some authors (e.g., Bartley

&

Chute. 1947; Smets et al., 1995;Vercoulen et al., 1998) developedatheory about the onsetand_perpetuation offatigue. Forexample,Vercoulen et al. (1998) have focussed on the persistenceoffatiguein CFS-patients. In their model of fatigue, attributioneffects,level ofphysicalactivity,senseofcontrol over

symptoms,andfocusing onbodily symptomsarecentral. Asanalternative, a biopsychosocial approach wasproposed as the mostsuitable wayofexamining fatigue(e.g., David et al., 1990; Lewis et al., 1992; Ware, 1993). The view that fatigueisrelated tovarious types

of

extreme stimulationinvolving low as well

as_{high physical and/or information-processing}demands (De Rijk,Schreurs, &

Bensing, 1999), andthebeliefthat fatigue linkswithsymptom perception

models(e.g., Pennebaker, 1982)arepromisingstepstowardsfurther theorizing (Finkelman, 1994).

In spite oftheeffortstodevelopsuch frameworks, inmostcurrent fatiguestudiesthe definition ofthe constructispoorlydescribed(Barofsky &

Legro, 1991). Nevertheless,_fatigueis_{often divided into physical}andmental components. Physicalfatigue refers to (i)an acutely painfulphenomenon

whicharises in overstressed musclesafterexercise(Grandjean, 1979), and (ii)

a_{symptom whichemerges}incircumstances suchas_{prolongedphysical}

exertion withoutsufficient rest orsleep disturbances due tomedication

DIMENSIONAI-ITY ANDASSESSMENT OFFATIGUE 15

competence andwillingness todevelop or maintain goal-directed behavior

aimed at_{adequate performances(Meijman} &Schaufeli, 1996). Chalder et al. (1993) supportedthis distinction. Gaillard (1996) assumed fundamental

distinctionsbetweenphysical andmental _{fatigue. Be that as it may, it is}

difficult

toseparate theseelements, duetocomplex interactionsbetween

physicalandmental elements in task andjobdemandsandconsequences of effort.

There is no consensus about the value ofthephysical versus mental contrast.Beforethe 1990s, fatigue was seen as aunidimensional construct (e.g., Lee,Hicks, & Nino Murcia, 1991). Thereafter, mainly due to the fast growing bodyofstudies on CFS,fatiguegained increased attention (Alberts.

Vercoulen,

&

Bleijenberg,2001). Nowadays, many authors conceive fatigue as amultidimensionalconstruct (e.g., Gawron,French,&Funke, 2001; Smets et

al., 1995). Forinstance. Smets et al. (1995)discernedfive_{components: general}

fatigue, physical fatigue, reduction inactivity,reductioninmotivation, and

mental _(cognitive)fatigue. Others, forinstanceSchwartz,Jandorf, and Krupp

(1993),developedthree-dimensional scales.Theseauthorsdistinguished the

followingfatiguedimensions: situation specific fatigue,consequences of

fatigue,and response toresUsleep.

Support forthemultidimensionality has beenobtained_{predominantly}

through factoranalyses and theemployment oftheeigenvalue exceedingunity

criterion (Kaiser. 1960) fordetermining thenumberoffactors (e.g.,Chalder et

al., 1993; Vercoulen et al., 1994; Vertommen& _{Leyssen, 1988).}However, this criterion oftenoverestimates the numberofdimensions bycausing factors to split intobloatedspecifics(e.g..Kline. 1987; Rummel, 1970). In contrast, a

few studies(e.g.. Smets et al., 1995) haveusedconfirmatory factoranalysis to demonstratemultidimensionality. Interestingly,when Smets et al. (1995) tested bothafive-factorsolution andafour-factor solution, an_{equalgoodness of fit} wasfound. Whetheraone-factor solution would fit thedataequally well was not examined.

Some researchers expressed serious doubtsregarding theputative superiority ofamultidimensional structureof_{fatigue. In}an_{explorativestudy}

of

the structureoffatigue,Studts. DeLeeuw,and Carlson(2001) failed to find

supportfordistinguishing cognitive, emotional,somatic, and general aspects of

fatigue. Ahsberg (2000)initiallydivided perceivedfatigue after work in lack of

energy,physical exertion,physical discomfort, lackofmotivation, and sleepiness. However, shenoted that, whiledistinguishingthese five

dimensions, lackofenergy appeared to beageneral latentfactor, that

16 CHAPTER 2

On account oftheongoing discussionabout thedefinitionandnature of fatigue,there is no standard waytomeasure the construct. Fatigue can be assessed _{usingobjective} measures such as reaction time or number of errors (Akerstedt, 1990),and_{subjectivemethods such as diaries (e.g., Vercoulen et} al., 1996),interviews(e.g., Meesters& Appels, 1996),and_{questionnaires (e.g..} Chalder et al., 1993). The applicationofquestionnaires is acommon_procedure

in large-scale studies. Recently, several questionnaires for_{measuringfatigue}

were reviewed_{by Friedberg andJason (1998)}andAlberts et al. _{(2001). These} reviewsdemonstrated that mostfatiguequestionnaires weredeveloped for specific patientgroups, suchas_patientswithcancer,multiplesclerosis, and

CFS (e.g., Fisk et al., 1994; Ray, Weir,Phillips,&Cullen, 1992; Smets, 1997;

Vercoulen et al., 1994), or forill_personsin_general (Alberts et al., 1997; _Krupp et al., 1989;Schwartz et al., 1993). Little isknown about theapplicability of

thesequestionnaires inhealthy populations. One of the fewquestionnaires developed for use in hospitalpopulations as wellas_{community populations is} theFatigue Scale (FS;Chalder et al., 1993). Thetworeviewsalsoreveal that multidimensional fatigue scales are seen as more comprehensive, and hence as more adequateforprovidinga_{completedescription of}anindividual's _fatigue

experience_{(Alberts et al.. 2001). The rationale for such a view isthatthese} scales takeinto considerationthat persons with thesameoverallscore nevertheless maydiffersubstantiallyintheirexperience (Smets et al., 1995).

However, itis admittedthatdisadvantages ofmultidimensional scales aretheir

length and, not seldom, thecontaminationoffatiguewith somaticillness.

Furthermore,theoverviews

of

fatigueassessmentinstruments showthatfatigue

is also_{frequentlymeasured using subscales}ofbroader measures. The

Emotional Exhaustionscale in burnout_{questionnaires (e.g.,MBI;} Maslach &

Jackson. 1996) andtheEnergyandFatigue subscale of theWorldHealth OrganizationQuality of Lifeassessment_{instrument (WHOQOL-100;}

WHOQOLgroup, 1995) are goodexamples ofthis approach.

Objectives of the present studies

The aim

of

Study I was toexamine the dimensionality offourfatiguescales in ahealthypopulation,inparticularasample thatisrepresentative of the

working population.Thesefour_fatigue scales arereliable,valid, and_frequently employed. InStudy II. a newfatigue instrumentwas administered to a

DIMENSIONALITY AND ASSESSMENT OF FATIGUE 17

Study I

Method

Participants

Sample 1 was used to test thedimensionalityoffatigue.Participants (n = 876) lived equally spread overthe Dutchregions and were obtainedvia random telephone calls. All selected respondentsworkedat least20 hours per week, and agreedtocompleteanumberofquestionnaires as part ofalongitudinal study. Intotal, 452 men (M =41.44 years, SD = 9.27, range 20-63 years) and

412 women (M =39.01 years. SD = 9.76, range 18-65) participated in this

study. Genderwas unknown for12_{respondents (total response = 48%). Of the} respondents 27% (n= 234) were single, and 638 persons(73%)were married

orlived together withapartner. Forty-six percent (n = 399) hadacollege education. Lower_{educated people were somewhat underrepresented andhighly}

educated personswereslightlyoverrepresented in this sample. However, this is not uncommon for this kindof_{study (Saris, 1988). The sample is}

representative fortheDutch working population (CBS, 1999),with respect to gender, maritalstatus. and age.

Measures

Sample 1 completedfourfatiguescales: the ChecklistIndividual Strength (CIS: Vercoulen et al., 1999),theEmotional Exhaustion subscale_(EEscale) from the Dutchversion ofthe Maslach_{Burnout Inventory (MBL}Maslach&Jackson,

1986:MBI-NL; Schaufeli &VanDierendonck, 1994),theEnergy andFatigue

subscale fromthe _{World Health OrganizationQuality of Life}assessment

instrument (WHOQOL-EF;WHOQOLgroup 1995. Dutchversion De Vries &

Van Heck, 1995), andthe_FatigueScale (FS; Chalder et al., 1993; Dutch

translation byDeVries, 1998).

TheCISconsists of20statements andprovidesa totalfatigue score, and scores forfour_componentsof_{fatigue: SubjectiveExperience} ofFatigue (SEF;

8 items), ReducedConcentration (CON; 5 items), ReducedMotivation (MOT:

4 items), and Reduced Physical Activitylevel (PA;3 _{items). Respondents use a} 7-point rating scale ( 1, yes, that istrue. to 7. no, that is not true). Thereliability

coefficient, estimated by lowerbound Cronbach's alpha, forthetotalscore was

90; and forthe_{subscales .88,.92,.83, and} .87,respectively (Vercoulen et al..

1999). The CIS showeddifferentscoresfor_{CFS-patients, MS-patients, and}

18 CHAPTER 2

was developedforCFS-patients, the questionnaireisclaimed to be also

appropriateforhealthy populations (Beurskens et al., 2000).

TheMBI-EEscale_comprises fiveitems, each with a_{7-point rating}scale

ranging from 1,never, to7,always. The scalehaswell-established validity and

a_{highreliability(coefficient alpha = .83) (Schaufeli & Van Dierendonck,}

1994).

The EFsubscale ofthe_WHOQOL-100containsfouritems with a 5-pointLikertscale(1, never, to5,always);twopositivelyphrased items using theword 'energy' and two negativelyphrased itemsusing the word '

fatigue'.

ItsCronbach's_{alpha was .95 and theEnergy}and_Fatiguescalecorrelated

highly withthe Fatigueand_{Vigorsubscales of the POMS (De}Vries & Van

Heck, 1997).

The 11-itemFSdistinguishesbetweenMental_{Fatigue (4 items),} describingcognitivedifficulties,and_{Physical Fatigue}(7items).Thismeasure usesa5-point ratingscale(1, never, to5,always). It isalsopossible to

calculateatotal fatiguescore. The scale wasfound to bebothreliableandvalid (Chalder et al., 1993)andshowed sensitivityto treatment changes (Deale, Chalder,Marks, Wessely, 1997).Cronbach's alpha fortheentire measure was

.89; and forthe subscales .82 and .85,respectively (Chalder et al., 1993). Statistical procedure

Means, standarddeviations,andCronbach's_{alpha were}calculated for each

(sub)scale. The associations amongthetotal scores oftheeight(sub)scales were_{calculated using Pearson}correlations.The_{dimensionality of the four}

fatiguescales was studied at theitem level by conducting exploratory factor

analyses(principalcomponents analyses),followed by Mokkenscaleanalyses

(Mokken

&

Lewis, 1982; Sijtsma, 1998; Sijtsma

&

Molenaar, in press). Both

exploratory factoranalysis andMokkenscale analysis were also conducted using the complete setofitems (k = 40) of thefourscales.In addition. factor

analyses wereconducted (i) atthe (sub)scalelevel of thefour_{questionnaires,}

and (ii) withthetotalscores of thefourquestionnaires.ForMokken Scale

Analysis, one can onlyuse _{single item}scores, not sumscores. Therefore, an analysis ofthetotalscores of the (sub)scales coold notbeperformed using this

procedure.

The screeplot (Cattell, 1966) ofthe exploratory factoranalyses was examined to scrutinizethedimensionality ofthefatiguescales.Mokken Scale

Analysiswas appliedbecausefactoranalysis isvulnerable tothe influence of differences intheitems' frequencydistributions (Nunnally, 1978), which may produce artifactual

'difficulty

factors'. Mokkenscale analysisisbased on the

scalability coefficient foritempairs.H(Molenaar, 1997), that equals theratio

DIMENSIONALrTY AND ASSESSMENTOFFATIGUE 19

univariate frequency distributions. In this way.theeffectofdifferent frequency distributionsiseliminated. Thus,Mokken scale analysis does not produce

artifacts duetodifferencesinfrequency distributions.

The_{computer program Mokken} Scale analysisfor_Polytomousitems

(MSP; Molenaar&Sijtsma, 2000) usescluster_analysisfor_selecting

unidimensional subscales froma_{larger set}ofitems. Each subscaleis selected

to optimize thescale H forthesubset

of

items selected (the scale H is a

weighted mean ofthe item pair Hs,asdiscussed before). For reliably ordering

persons ona (sub)scale,the scale H has to beatleast .3_{(default in MSP;}

Molenaar

&

Sijtsma, 2000). However, highervaluesaredesirable because they

indicate highermeasurement _{reliability, and}a scale H > .5is_{interpreted as}

indicative ofa_strongscale.The_qualityof individualitems ascontributors to reliable personorderingisguaranteed by only admitting items toascale if the item scalability coefficient (ite,n H; a_{weighted mean of all item pairHs in}

whichthe studied_{item figures) is}atleast.3_(Molenaar&Sijtsma, 2000). MSP is one of the few programs for itemresponsetheory analysis (VanderLinden & Hambleton, 1997) that hasanautomateditem_{selection procedure.}

Results

Means, standarddeviationsandCronbach's _{alphas of thefatiguequestionnaires}

are shown inTable 2.1. _Inspection oftheseresults reveals that no excessive

high orlowscoreswerefound in this _sample.

The scree_plots(Cattell, 1966) based on_{exploratory factor}analyses revealed thatMBI-EE,WHOQOL-EF, and FS wereeachbased on onefactor (see Figure 2.1 forthescree plots).The single factors extracted from the

separate scalesexplained between 40% (FS) and69%(WHOQOL-EF) of the

(observed) variance. Thescree plot of the ClSsuggested theextraction of

eitheronefactor orfourfactors. MokkenScale _{Analyses, on}the other hand, showed thateachquestionnaire formedonereliablescale_{(Table 2.2).}

Therefore, itwas conluded that the CIS is alsobest conceived of as a

unidimensional scale.Thefactorstructure and the _{scalability,using}coefficient H of thefour_{questionnaires, were}exploredseparately.

Exploratory factoranalysis at the item level, usingthetotal set of 40 items of thefourscalestogether, yieldedonefactor,thatexplained42% of the

total_{variance. Based on recommendations by}Hemker, Sijtsma, andMolenaar (1995), MSP was usedwithscalability lowerbounds of .0,.3,.4, and .5, respectively, for itemselectionusing all40 items.Followingtheseauthors' rules

of

thumbforinterpreting theresultsfromapplyingtheclusteranalysis

fourtimes usingdifferentlowerbounds,

it

couldbeconcluded that37items

formed one reliable scalewithscaleH = Al (Table 2.2). Values between .4 and

20 CHi\FIER 2

7) and one FS item (number 11)measured anothertrait than the 37 selected items. Table 2.2 shows thatthe itein Hs varied from .34 to .56, meaning that

itemscontributedifferently tothereliability ofthepersonorderingbased on all 37 items.

Table 2.1

Mean, Standard Deviation, and Reliability Coefficient of the (Sub)scales

(Sub)scale M SD _Alpha CISTotal 51.25 23.70 .94

CIS-SubjectiveExperience ofFatigue 22.59 22.59 .93

CIS-ReductionofConcentration 12.13 6.87 .88

CIS-ReductionofMotivation 10.04 5.25 .82

CIS-Reductionin Level of_{PhysicalActivity} 6.60 4.16 .84

MBI-Emotional Exhaustion 2.57 1.12 .87

WHOQOL-EnergyandFatigue 10.08 2.75 .85

FatigueScaleTotal 19.80 5.86 .87

FS-Mental _Fatigue 6.90 2.15 .76

FS-Physical Fatigue 12.90 4.45 .85

Note. CIS =Checklist_{Individual Strength, MBI} = Maslach Burnout Inventory, WHOQOL=World_{Health OrganizationQuality of Life}

assessmentinstrument; FS =FatigueScale.

Table 2.2

Results of Mokken Scale Analyses per Scale (loiverbound = .3)

Scale K _{n H Min(item/f)-max(itemH)}

ChecklistIndividual _{Strength 20} 849 .47 .31 - .56

MBI-EmotionalExhaustion 5 872 .59 .51 - .66

WHOQOL-Energy+Fatigue 4 857 .70 .68 - .73

FatigueScale _{10 (Iteml 1 removed) 872} .48 .37 - .56

Complete set of40 items 37 832 .47 .34 - .56

Fatigue AssessmentScale 10 1835 .47 .37 - .55

Note. MBI =Maslach _{Burnout Inventory;WHOQOL= World Health}

Table 2.3

Correlations among the (Sub)scales

(Sub)scale 1 2 3 4 5 6 7 8

1._{CIS-Subjective Experience}of_{Fatigue --} .58 .65 .49 .60 .78 .43 .78

2. CIS-ReductionofConcentration -- .55 .54 .48 .51 .66 .54

3. CIS-Reductionof Motivation -- .55 .49 .59 .44 .58

4. CIS-Reduction inLevelof_{PhysicalActivity --} .34 .48 .42 .44

5. MBI-Emotional

Exhaustion --

.62 .46 .63

6. WHOQOL-Energy and_{Fatigue --} .44 .76

7. FS-Mental Fatigue -- .54

8._{FS-Physical Fatigue}

--Note. All ps < .001. CIS=ChecklistIndividual Strength, MBI=Maslach Burnout Inventory; WHOQOL=WorldHealth

C

OrganizationQuality of Lifeassessmentinstrument; FS =Fatigue_{Scale. 2}

22 CHAPTER 2 10 -

10-1 8 '.

3 6.

iii 2 - L

& 4.

if 2 =

o . I.-I i - i - 1 - i ·, O 1 I 1

1 3 5 7 9 11 13 15 17 19 1 2 3 4 5

Component number CIS _{Component number M Bl-EE}

CIS = Checklist IndividualStrength MBI-EE= Emotional

Exhaustionscale from the

Maslach Burnout Inventory

1010 -8•

3 8. f

I 6.

3 6.

C

-&

4.

_4.

m _2• 2· O 1

.0

. 1/k 1 2 3 4 1 3 5 7 9 11

Component number WHOQOL-EF Componentnumber FS

WHOQOL-EF= EnergyandFatigue scale FS = Fatigue Scale

fromtheWorldHealth Organization

Quality of Lifeassessmentinstrument

Figure2.1. Scree plot of the item-level factor analysis on the four fatigue

questionnaires.

Thecorrelationsbetween the scores oftheeight(sub)scales were moderate to strong, ranging from .34 to .78 Call ps < .001); see Table 2.3. The

Cronbach's_{alpha of the}used (sub)scales was satisfactory, withthe alpha's ranging from .76(FS-Mental Fatigue) to .94 (CIS Total). The scores of the four

subscales of the CIS, thetwosubscales of the FS. the WHOQOL-EF. and the

MBI-EEwere subjected toafactoranalysis, and the screeplot (Cattell. 1966)

indicated as onefactor.This _{factor explained 61% of}the_{variance. Separate} analyses. notreported here.revealed that thesame strongone-factor solution was found, whenthe samplewassplitaccordingtogender and age. The same results were alsoobtained when only thetotalscores of thefourscales.

DIMENSIONALITY AND ASSESSMENTOFFATIGUE 23

Tosummarize, factoranalysesconsistently revealed onefactor, both at

the item as well as the (sub)scalelevel. Neithergender noragegroups

influencedtheseoutcomes. MokkenScale Analyses alsoyieldedaone-scale

solution. So. the four questionnaires used in this study all seem tomeasureone construct: fatigue.

Discussion

Exploratory factoranalyses for thefour fatiguequestionnairesconsistently

indicatedonefactor both at the item level and atthe(sub)scale level.Mokken

Scaleanalyses alsoresulted in aone-scale solution. So, thefourquestionnaires

used inthisstudy all seem to measureone unidimensional construct. The unidimensionality ofthe constructfatigueallows fortheconstruction of a new,

short, and easytoadministerscale.

Study II

The aimofStudy 11wastwofold: toconstruct anewself-reportfatigue instrumentandsubsequently to test its contentvalidityandreliability. Method

Participants

Twolarge respondent groups participatedin Study II. Sample 1 was used to construct the new fatigue scale: Sample 2 was thevalidation group. Sample 1

(n = 876)was_{described above. Participants in Sample 2 (n -} 1.893),which was arepresentative sample oftheDutch population.completed a

computer-administered_{questionnaire. Therespondents of}the latter_{sample were all}

members ofan internet-based telepanel. Every weekaquestionnaire.which

was downloaded from the telepanel'sinternet site. wasadministered to this

panel ofaround approximately2000 households. The sampleconsisted of

1.128 men (age: M = 46.37 years. SD = 15.44, range 16-87 years) and 765 women Cage: M - 42.17 years. SD = 14.66. range 16-87 _{years). Fifty-seven}

percent ofthetotal group had a paidjob.Twenty-fourpercent (n = 454) had a

college education. Prc,cedure

First, items wereremoved.which could onlybe_{completed byspecific} groups (e.g.. workers).items askingtwothings at the same time,oritemswhich had a

24 CHAFTER 2

the remaining item pool.TheWHOQOLGroup (1998) also used this method.

Two reasonsexistforselectingitems for the FAS onasemantical basis. The

FAS isconstructed to representall semanticalfatiguecategories.A purely statisticalselectionofitemswouldnot_likelycoverall kindsofdifferent

experiences ofbeingtired. For instance,this could have led to a set

of

items that wasonlyrelated to physicalfatigue. Secondly,a statisticalselectionwould

be based on data

of

workingrespondents.Itmightbepossible that adifferent

statisticalselectionwouldbeobtained when dataof_{patients were analyzed.}

The generalizability oftheselection wouldbequestionable in this way. Thus, a

contentanalysis ofthequestions was done inordertoidentifysemantically equivalentquestions. The numberofquestions was hereby reduced. Questions

with limitedfacevalidity were deleted. Theitems were thengrouped into

categoriesreflectingasimilar type

of

fatigue. Judgements by thefirst two

authors regardingsemantical _equivalenceand_{categorization}were based on consensual agreement. Afterthesemantical analysis, per semantical group the

item withthe highest factor loading onthe one-factorsolution of the40items was chosen. In addition,anextra_{item concerning mental}exhaustion was

included. Thereasontoincludethis particular item wastoensure that the two domainsof_{fatigue, which are} mostoften used(mentaland_{physicalfatigue),} wereaskedabout inabalancedway.Subsequently, the new 10-item scale, the Fatigue Assessment_{Scale (FAS),} was presentedto Sample 2. For examining

the _{psychometric qualities of the FAS, Cronbach'salpha was calculated, and}

factor_{analysis and}Mokkenscale_{analysis were conducted at the}item level.

Results

Twelve ofthe_fortyitems wereremoved beforethe semantical analysis. Among

these werefivework-relateditems (e.g., MBI 'I feel used up at the end of the

workday'),aquestion asking about twothings at the same time (FS 'Do you

feel sleepyor drowsy?'),anditemswhich werenotstronglyrelated tofatigue (FS 'Do you makeslips ofthetongue when speaking?'). There appeared to be

nine_{semantical groups}

of

items: (i)beingbotheredby fatigue (twoitems; e.g.,

'Do youhaveproblems with_{tiredness' FS 1), (ii)feeling physically tired (nine}

items;e.g., 'Physically, Ifeelexhausted' CIS4),(iii) speedofgetting tired (two

items; e.g., 'I gettired very quickly' CIS 16), (iv)levelof_{energy (three items,}

e.g., 'Are youlacking inenergy' FS6), (v) concentration(five items: e.g., 'I can

concentrate well' CIS 1 1), (vi) inability of thinkingclearly (two items; e.g., 'Do youhaveproblems thinkingclearly' FS 10),

(vii)

quantityofdaily activities

(threeitems; e.g., 'Ido_{quite a}lotwithin a day' CIS7),(viii) problemsto start things (one item; 'Do youhaveproblems starting things' FS4), and(ix)feeling

no desire to do anything (1 item; 'I feelnodesire to do anything' CIS 18).

DIMENSIONALITY AND ASSESSMENTOFFATIGUE 25

highestfactor loading ofthe semantical group onthe factor thatwas identified

in the40-item factoranalysis, performedin Study I. As explainedabove, an extraitem concerningmental fatiguewas included in thetest population. Thus,

theFASconsists oftenitems(see Appendix). A5-pointLikert frequency

ratingscale, ranging from nevertoalways. was chosen toaccompanythe items.

Cronbach's alpha of the FAS was .87. Factor analysisindicated that the

tenitems measured one_{factor, explaining 48% of}thevariance(seeTable 2.4

and Figure 2.2), also when menandwomen oragegroups were separated. Based onitemselection using severallowerboundvalues for H, Mokkenscale analyses revealed that the ten itemsformedone_{reliable scale (H = .47).}

Individual itemHs varied from .37 to .55 (Table 2.2). Also here, our conclusion

is that the 10items measure the sametrait. Discussion

Thefour fatiguequestionnaires used in Study 1 all appeared to be

unidimensional. Consequently, fatigue isassumed to be oneconstruct. A new,

10-itemfatiguemeasure, the Fatigue Assessment Scale (FAS), was

constructed, based onasemantical_{analysis of}the_fortyitems of the four

questionnaires,employed in Study I. The FAS has_{promising psychometric}

qualities.

The findings in Study I regarding thedimensionality

of

fatigue are in line withthe ideasofLewis and_{Wessely (1992), who conceived}of_{fatigue as a}

continuum. However,they assumed that, whenfatigue ismeasured with emotional, behavioral,andcognitive components, itis likely thatthe concept is

multidimensional. Thelatter view also reflectsthe ideas

of

Smets et al. (1995) and Gawron et al. (2001), whoargued that. despite the absense ofadefinition offatigue,thereis agreement thatfatigue isamultidimensional concept. The

present study does notsupportthisposition. Forinstance, the CIS, which is

supposed to measurefourseparatedimensions

of

fatiguein patient populations

as well as inthepopulationofworkers, showedaclearunidimensional

structure inoursample. Inrelation to this, it isquite remarkable thatthecut-off point forthe_{multidimensional CIS,}toindicatea fatiguelevel whichshows that

someone is at risk for sick leave orwork disability, isfixed onthetotal score

(Bultmann et al., 2000), and is not acombinationof cut-offpoints for the four

dimensions.This seemstosupportour findings.

Apossible reason whythe resultsofStudy I donot support

multidimensionalitycould be that, comparedwith_groups of_{predominantly}

healthypersons,patientsfocus moreon symptomsand,therefore, distinguish

more aspects offatigue. Maybe fatigue isunidimensional fornon-patient

groupsand multidimensionalfor_patients. However,Studts et al. _{(2001) found}

26 CHAPTER 2

andhealthy controls.Hopefully, the outcomes

of

Study I

will

reopen the discussion aboutthedimensionalityoffatigue.

Table 2.4

Factor Loadi„gs of the FAS-items, ordered by Size

FAS-item Fatigue

I get tired veryquickly .78

Physically, Ifeel exhausted .77

I am bothered_{by fatigue} .76

Mentally. I feel exhausted .74

1 feel nodesire to doanything .67

I don't domuch _{during theday} .65

Ihave problems tothink clearly .65

Ihave problemstostartthings .64

I_{have enough energy}for_{everyday life} * .63

When I am_{doingsomething. I} can concentrate_{quite well}* .57

* = recoded item.

Forpractical reasons, it wasimpossibletoinclude all relevant fatigue

questionnairesinStudy I.Therefore.aselection

of

questionnaires had to be made. Thefourinstruments thatwere chosen arereliable, valid.and_frequently usedin Western_{countries. To our knowledge,} thisselectionofmeasuresforms

a_{goodrepresentation of}theavailable unidimensionalandmultidimensional fatiguequestionnaires. The useofother assessment instruments might have led todifferent results. Itisinteresting tonote,however, that this study is not the

onlyone, which foundaone-factorial solution_{usingpurportedly}

multidimensionalinstruments. Studts et al. (2001) alsofounda one-factor solution indataobtainedwithseveral_{other ostensibly multidimensional fatigue} questionnaires. Inconclusion. fatigueseems to be aunidimensionalconstruct.

5 4-. 3. .S2. La 1.

f , .--...

0 . 12345678 9 10 Component number

DIMENSIONALITY AND ASSESSMENT OF FATIGUE 27

In Study II, a new, 10-itemfatigue scale, the FAS, wasconstructed. basedon semanticalandempiricalconsiderations. Subsequently. this instrumentwas tested inalarge sample, representative forthe Dutch

population.Thereliability of the FAS wassatisfactory. Inaddition. itcould be shown that the FAS measures one construct. namelyfatigue.This outcome was also obtained whenseparate analyses were conducted on subgroups (gender or

different agegroups). Similarly. Mokkenscale analyses revealed that the ten

FAS-items formedonereliable scale. In sum. the FAS has_{shown good}

psychometricqualities ina_{representative}Dutch population.

The test sample in this study was arepresentative sample from the Dutchpopulation. Not much can be saidaboutthe applicabilitytoother groups.

for_{example,patientssuffering from a lung}disease, _{cancer patients, and so on.}

in futureresearch itwouldbeinterestingtocompareFAS-scores in healthy

workingpeople, working but

ill

people, and

ill

peoplewho cannot work due to theirdisease. Furthermore.itcouldbeargued that thedifference in

questionnaireadministration (paper-and-pencilversus computerized) could

leadtodifferentresponse patterns.However, Mitchell,Klein, andBalloun

( 1996) found that modeofadministration, paper-and-pencil or computerized. didnot_{impact findings.} In_{addition, in}a_{study by}Gaudron (2000), computer

anxiety didnotartificiallymodify scores_{during computer administration.}

In conclusion. a 10-item_{unidimensional fatigue questionnaire (FAS)} wasdeveloped,whichisshort and easy to use. Its psychometric qualities are promising,butrequire further examination infuture research.

References

Ahsberg. E. (2000). Dimensionsoffatigue in different working populations. Scandina\,ian Journal of Psyclic,logy, 41,231-241.

Akerstedt. T. ( 1990). Psychologicaland psychophysiological effectsofshift work.Scandinavian Journal c,f Work, Eni,ironment & Health, 16.67-73.

Alberts, M., Smets, E. M. A., Vercoulen, J. H. M. M.. Garssen, B., & Bleijenberg, G.(1997). 'Verkorte vermoeidheidsvragenlijst': Een praktischhulpmiddel bij het scorenvan vermoeidheid _['Shortened Fatigue Questionnaire': A practical aid in scoringfatiguel.Nederlands Tijcischrift voor Geneeskunde, 141, 1526-1530.

Alberts. M., Vercoulen, J. H. M. M.,& Bleijenberg, G. (2001).Assessment of fatigue. Theapplication ofthe_{subjective feeling} of_fatigue indifferent

research studies. In A. J. J. _{M. Vingerhoets (Ed.).}Assessment in

behavioral medicine_{(pp. 301-328). Hove,} UK: Brunner-Routledge.

Barofsky. 1., & Legro. M. W. (1991).Definition andmeasurementof_fatigue.

Rei,ie„·s of Infectious Diseases. 13.94-97.