Irritable bowel syndrome (IBS) is a long-term andepisodic medical disorder shown to have an impacton work productivity and health-related quality oflife (QOL). The objective of this study was to assessthe impact of IBS on work productivity and onhealth-related QOL in an employed population inthe United States and to quantify the cost of thesefactors to the employer. A 2-phase survey was sentto the workforce of a large US bank to assess thepresence of IBS among employees and to measuretheir work productivity (absenteeism [time lost fromwork] and presenteeism [reduced productivity atwork]) and health-related QOL. Forty-one percent ofthe 1776 employees responding to both phases ofthe survey met the Rome II criteria for IBS.Employees with IBS reported a 15% greater loss inwork productivity because of gastrointestinal symptomsthan employees without IBS and had significantlylower Medical Outcomes Study Short Form36 (SF-36) scores than those without IBS. IBS wasassociated with a 21% reduction in work productivity,equivalent to working less than 4 days in a 5-dayworkweek. Employees with IBS also had significantlylower scores on all domains of the SF-36, indicatingpoorer functional outcomes. Reduced workproductivity and diminished QOL of these magnitudesmay have substantial financial impact onemployers.
(Am J Manag Care. 2005;11:S17-
Patients with irritable bowel syndrome(IBS) report symptoms that may waxand wane in type and severity overtime1,2 and that can have a negative impacton health-related quality of life (QOL).3-6 IBSaffects adults of all ages, primarily those ofworking age (30-50 years old).2 In the UnitedStates, an estimated 10% to 20% of adults arebelieved to have symptoms consistent withthis disorder.3
Although estimates of the direct costsassociated with IBS are staggering and canvary greatly,7 the impact of IBS on absenteeism(hours absent from work), presenteeism(reduced productivity while at work),and health-related QOL is of increasing concernto employers in the United States, whorely heavily on a healthy workforce and whocontract with health plans and other payersto cover the healthcare costs of their employees.For these reasons, employers oftenimplement wellness and disease managementprograms to optimize workforce health.
Leong and colleagues8 studied healthcareinsurance data of the employees of a self-insuredFortune 100 company and determinedthat direct and indirect costs forpatients with IBS were substantially greaterthan those for a matched non-IBS controlgroup. In 1998, the direct and indirect medicalcosts to the employer for 1 employeewith IBS were $3997 and $2367, respectively,which were $1651 and $468 greater thanthe direct and indirect medical costs for 1employee without IBS. The indirect cost forpatients with IBS is likely to have beenunderestimated, however, because this estimateincluded absenteeism but not presenteeism.
Hahn and colleagues9 measured the impactof IBS on absenteeism. Although the actualnumber of hours employees were absent fromwork because of IBS was not substantial, thenumber of missed workdays increased significantlyas the severity of illness increased. Ina separate study of IBS patients, Hahn andcolleagues10 found that Medical OutcomesStudy Short Form 36 (SF-36) scores ofrespondents from the United States and theUnited Kingdom were significantly lower,meaning that they were worse than therespective population norms. Moreover, 30%of US respondents missed at least 1 full dayof work in the 4 weeks preceding the survey,and 46% reported "cutting back" onsome workdays because of IBS.
Although several studies have reportedreduced health-related QOL in IBS populations,3-6 limited research has been conductedto assess health-related QOL or absenteeismin an employed population with IBS, andeven less research has been conducted toquantify the economic impact of these factorson the employer. Additionally, thesestudies have largely ignored the specificimpact of IBS-associated gastrointestinal(GI) symptoms on presenteeism.
Our objective was to assess the impact ofIBS on work productivity (presenteeism andabsenteeism) and on health-related QOL ina US employed population and to quantifythe cost of these factors to the employer.
Participants were employees of ComericaIncorporated, a nationwide bank with majorbranches in multiple states (Michigan,California, Texas, and Florida). From April2002 to August 2002, all employees ofComerica (N = 11 806) were invited to participatein a 2-phase survey regarding GIhealth and related symptoms.
All Comerica employees were mailed asurvey designed to (1) identify those with IBS(including subgroup classification for constipation[IBS-C] or diarrhea [IBS-D]) using theRome II criteria11-13; (2) measure the frequency,severity, and bothersomeness of IBSsymptoms; and (3) capture information onsociodemographics, long-term health conditions(including physician-diagnosed IBS),and job characteristics. A postcard wasincluded in the initial mailing to requestsigned consent for participation in the followupsurvey. Employees who completed initialsurveys and consent forms received a secondsurvey measuring work productivity loss becauseof IBS and assessing QOL (Figure 1).The Cedars-Sinai Health System InstitutionalReview Board approved this study.
Names of initial survey participants wereentered in a raffle for 1 of 9 gift checks valuedbetween $100 and $500. Second-phasesurvey participants received a gift check for$25. All participants received educationalmaterial regarding IBS at the conclusion ofthe study.
Rome II Criteria.
Employees were administeredthe Rome II diagnostic criteriaquestionnaire11-13 to assess the presence ofIBS. According to the Rome II criteria, IBS isdefined by the presence of abdominal discomfortor pain for at least 12 weeks, whichneed not be consecutive, during the preceding12 months, and the discomfort or painshould have 2 of the following 3 features: itshould be relieved with defecation; its onsetshould be associated with a change in thefrequency of the stool; its onset should beassociated with a change in the form (appearance)of the stool.13 Supportive symptomscan be used to classify IBS patients intosymptom subgroups: IBS-C, characterized byless than 3 stools per week, hard/lumpystools, straining, and feeling of incompletebowel evacuation; IBS-D, characterized bymore than 3 stools per week, loose or waterystools, and urgency; and mixed-pattern subtypes(alternating IBS).13,14
Assessment of Work Productivity.
Workproductivity was measured using the WorkProductivity and Activity Impairment (WPAI)questionnaire,15 which was developed andvalidated as a general health measure thatcan be easily modified for specific healthconditions. Adapted versions of the WPAI16have been developed for use in patients withconditions such as allergy,16,17 long-termhand dermatitis,18 and gastroesophagealreflux disease (GERD).19,20 We adapted theWPAI to estimate the impact of GI symptomsconsistent with IBS, including abdominalpain or discomfort, bloating, and constipationor diarrhea, on work productivity.16 Areasassessed included level of impairment duringwork and other daily activities and hoursabsent from work because of IBS symptomsduring the previous 7 days. A scale from 0 to10 was used to assess the degree to which GIsymptoms consistent with IBS negativelyaffected a patient's productivity while workingand to assess how they affected dailyactivity. Measures of productivity and absenteeismwere combined in the work productivityscore (WPS), which quantifies reducedwork productivity (absenteeism and presenteeism)attributed to GI symptoms consistentwith IBS as a percentage of potential totalwork productivity during a full-time workweek.The WPS was calculated as follows:
WPAI measures are interpreted as a percentagereduction in productivity (or a percentageof productivity lost) and areadjusted for part-time status. For example, aWPS of 5% indicates that a full-time employeeis working at only 95% of full work potential(eg, 40 hours) because of reductionsassociated with absenteeism and presenteeism.A WPS of 5% for an employee working40 hours per week would imply areduction of 2 hours of potential work productivitylost.
Medical Outcomes Study Short Form.
QOL was assessed using the SF-36 questionnaire,a generic instrument designed tomeasure overall health status.21,22 TheWPS = [(hours absent from work + percentage of reducedproductivity at work × hours actually worked)/(hoursmissed because of ill health + hours worked)] × 100.SF-36, which has previously been validatedfor use in the measurement of health-relatedQOL among IBS patients,23 assesses healthstatus across 8 subscales, including physicalfunctioning, physical role limitations, emotionalrole limitations, social functioning,bodily pain, general mental health, vitality,and general health perceptions. Additionally,subscale scores can be collapsed into 2summary scores, the mental componentsummary (MCS) and the physical componentsummary (PCS).24 Scores for each subscaleand summary score range from 0 (poorhealth) to 100 (optimal health).
Employees meetingthe Rome II criteria for IBS were comparedwith those not meeting the criteria withrespect to a variety of variables, includingdemographic and work-related measures,presence of comorbid conditions, and historyof hysterectomy or surgeries of the GItract. Chi-square tests were used for categoricalvariables and tests for continuousvariables. Two-sided values were calculated,and statistical significance was set at theκ= 0.05 level.
The kappa coefficient was calculated toassess the agreement between respondentsmeeting the Rome II criteria (based on thequestionnaire) and respondents indicating adiagnosis of IBS by a physician or anothermedical professional (formal diagnosis). Thekappa statistic describes the degree of agreementbetween 2 variables. Kappa valuesrange between -1.0 (perfect disagreement)and +1.0 (perfect agreement), with zeroindicating agreement that is completelyaccounted for by chance. Values of 0.0 to 0.2indicate slight agreement, 0.2 to 0.4 fairagreement, 0.4 to 0.6 moderate agreement,0.6 to 0.8 substantial agreement, and 0.8 to1.0 near-perfect agreement.
Employees with and without IBS (asdetermined by their having met the Rome IIcriteria) were compared with respect tomean percentage reductions across WPAImeasures of productivity, and a similar comparisonwas made between IBS-C and IBS-Dsubgroups. A nonparametric method, bootstrapping,was used to estimate the 95% confidenceinterval (CI) for differences inproductivity impairments. Bootstrapping is astatistical approach for estimating CIs fromdata simulations when distributions deviateconsiderably from the assumptions of parametricstatistics. Mean percentage reductionsin WPAI measures of productivity wereconverted to lost work productivity based ontotal number of hours absent from work(absenteeism) and total number of hours atreduced productivity while at work (presenteeism)based on a 40-hour workweek (usingthe WPS formula presented in this article).These hours were also quantified based onthe mean salary and mean wages of employeesin the sample. The mean cost in dollarsof reduced work productivity (absenteeismand presenteeism) per year (assuming full-timeemployment of 2080 hours of potentialwork time annually per employee) becauseof GI symptoms consistent with IBS was calculatedas the difference in cost of reducedwork productivity between employees withand without IBS. The cost per employee wasextrapolated to a company with 10 000employees assuming IBS prevalence estimatesranging from 10% to 20%.
Health-related QOL scores were calculatedfor the MCS and PCS and for each of the8 SF-36 subscales. Mean differences inscores between IBS and non-IBS groups andbetween IBS-C and IBS-D subgroups werecalculated with 95% CI.
Survey participation is outlined in Figure1. The initial survey was sent to all 11 806Comerica employees and was returned by2615 (22.2%) employees. Compared withthe general Comerica employee population,respondents were similar in age, sex, andwork status (full-time vs part-time). Completedsurveys along with consent forms weresubmitted by 2276 (87.0%) employees, whothen received the phase 2 survey; that surveywas completed by 1776 (78.0%) of the initialrespondents. The 1776 phase 2 respondentswere similar to the 500 phase 2nonrespondents in age, sex, education,compensation type (salary vs hourlywage), and work status (full-time vs part-time)(>.05 for each). However, those whocompleted the survey were more likely to bewhite (= .0002).
Among the 1776phase 2 respondents, 720 (40.5%) employeesmet Rome II criteria for IBS. Of these, 191(27%) and 255 (35%) met Rome II IBS subtypecriteria for IBS-C and IBS-D, respectively;the remaining 38% reported mixed-patternbowel habit. Employees with IBS were similarto those without IBS (n = 1056) in age,compensation type (salary vs hourly wage),and work status (full-time vs part-time)(>.05 for each) (Table 1). Employees with IBSwere more likely to be women (<.0001)(man/woman ratio, 1:5.1), were less likely tohave a graduate degree (= .03), and differedslightly with regard to race and ethnicity(= .04). Employees with IBS were alsomore likely to have allergies, anxiety,depression, GERD, stomach ulcers, gallstones,and incontinence than employeeswithout IBS (<.001 for each).
Symptoms of abdominal pain or discomfort,diarrhea, constipation, gas, and bloatingwere each significantly more frequentand severe among employees with IBS thanamong those without IBS (<.05). In addition,the IBS group reported greater levels ofdistress (moderate to extreme) because ofeach of the above symptoms than the groupwithout IBS (<.05). The greatest differencesin reported frequency of symptomsbetween employees with and without IBSwere for abdominal pain or discomfort andbloating, whereas the greatest reported differencesin distress were attributed to thesymptoms of constipation, diarrhea, andbloating. Exploratory and excisional surgeriesassociated with abdominal pain or symptomswere significantly more commonamong employees with IBS (Table 2), aswere other types of surgery, such as appendectomy,cholecystectomy, and hysterectomy(<.05). Small bowel resection and obstructionwere more common among employeeswith IBS (= .06).
Agreement Between Rome II Criteria
and Professional Diagnosis of IBS.
Data from the initial survey responders(n = 2615) were used to assess agreementbetween employees meeting Rome II symptomcriteria (n = 1042) and those reportinga previous diagnosis of IBS determined by aphysician or another medical professional(n = 269) (Figure 2). Agreement between adiagnosis of IBS by a physician or a medicalprofessional and a diagnosis of IBS using theRome II criteria was low (κ= 0.22), indicatingthat most patients whose IBS was diagnosedusing the Rome II criteria had notbeen previously diagnosed by a physician ora medical professional. Among employeesreporting a previous diagnosis of IBS by aphysician or another medical professional,86% (n = 230) met Rome II criteria; in comparison, of the 2346 employees who did notreport a diagnosis of IBS by a physician or amedical professional, 35% (n = 812) metRome II criteria. Thus, the Rome II capturedmost of the IBS diagnoses previouslymade by a physician or another medicalprofessional, and it was also able to capturea significant number of IBS cases that hadnot yet been formally diagnosed. Of thetotal number of respondents who met RomeII criteria during the initial survey (n =1042), 22% (n = 230) also reported IBS previouslydiagnosed by a physician or anothermedical professional, whereas only 2% (n =39) of employees not meeting the Rome IIcriteria for IBS (n = 1573) reported a physicianor a medical professional diagnosis ofIBS. Thus, the proportion of diagnoses by aphysician or a medical professional thatwere not identified using the Rome II criteriawas small.
Impact of IBS on Work Productivity.
Figure 3 provides measures of work productivity(absenteeism and presenteeism) andactivity impairment for employees with andwithout IBS. Among employees with IBS,productivity at work (presenteeism) wasreduced by more than 21% because of GIsymptoms consistent with IBS; this figurewas 15% (95% CI, 13.4-16.6) higher than thatreported among employees without IBS. Thepercentages of work time missed (absenteeism)were 1.7% and 0.4% (mean percentagedifference, 1.3; 95% CI, 0.7-1.9) among thosewith and without IBS, respectively.
The largest contributor to total productivityloss, WPS, was reduced productivity atwork (presenteeism) (15%; 95% CI, 13-17). Incomparison, absenteeism contributed onlyslightly to the total WPS (1.3%; 95% CI, 0.7-1.9). GI symptoms consistent with IBS wereassociated with a 21.1% reduction in totalWPS among employees with IBS comparedwith a 6.1% reduction among those withoutIBS. Reductions in total WPS among employeeswith IBS-C and IBS-D were comparable at18.2% and 20.8%, respectively. Based on theaverage hourly wage of each employee, reductionin total WPS resulted in average losses of$10 884 and $3147 for employees with andwithout IBS, respectively. Thus, the value ofwork productivity loss per individual becauseof IBS-attributable GI symptoms was $7737(95% CI, $7332-$8143) per year.
Employees with IBS reported a meanreduction of nearly 27% in regular dailyactivities (ie, work around the house, shopping,childcare, exercising, studying) becauseof GI symptoms consistent with IBS.This accounted for the largest differencebetween IBS and non-IBS employees, asshown by a 19% (95% CI, 16.9-20.7) meandifference in daily activity impairment.
Impact of Work Productivity Reduction
on the Employer.
The incremental work productivityloss associated with IBS representsan additional 39 days of reduced productivityat work and an additional 3.4 days of absenceper year for each employee with IBS.Assuming participants are representative ofthe Comerica employee population (10 000employees) and assuming a 10% prevalence ofIBS, the employer loses a total of $7 737 600per year. If the prevalence of IBS is 20%, theresultant work productivity loss increases to$15 475 200 per year. Among salaried employeeswith IBS (n = 481), mean work productivitylosses attributable to GI symptomsconsistent with IBS ranged from 19% to 21%,regardless of salary range ($15 000-$35 000,$35 000-$55 000, $55 000-$80 000, and>$80 000). In contrast, hourly employeeswith IBS earning ≤$15 per hour (n = 155)experienced a 44% greater work productivityloss than those with IBS earning >$15 perhour (n = 100) (26% vs 18% work productivityloss for ≤$15 per hour vs >$15 per hour,respectively).
Impact of IBS on Health-
Scores for all SF-36 subscales were significantlylower for employees with IBS than forthose without IBS (<.05) (Figure 4). Themost significant difference was in physicalrole limitations, with a mean difference of24.6 (95% CI, 21.4-27.7) points betweenemployees with and employees without IBS.Compared with subjects with IBS-D, thosewith IBS-C scored lower on the MCS andreported greater impairment on 6 of 8 SF-36domains (although only emotional role functioningwas statistically significant).
MCS and PCS scores were lower amongemployees with IBS than among those with-out IBS, with mean differences of 5.9 (95%CI, 5.0-6.9) and 5.4 (95% CI, 4.7-6.0),respectively.
IBS is a long-term and episodic disorder,with GI symptoms (abdominal pain or discomfortand bloating associated with alteredbowel function) that can wax and wane andthat affect many persons during their mostproductive years of adulthood. This study isone of the first evaluations performed in aUS employed population that measure theimpact of IBS on work productivity and onhealth-related QOL. We found that IBS issignificantly associated with reduced workproductivity and that it significantly impactshealth-related QOL, suggesting that managementstrategies targeting improvements insymptoms consistent with IBS and health-relatedQOL should be expected to have apositive impact on work productivity.
Reduced productivity while at work (presenteeism)because of GI symptoms consistentwith IBS was a major contributor tototal reduced work productivity. Employeeswith IBS experienced an additional 15%reduction in work productivity beyond thatreported among controls. For an employeewho works 40 hours per week, this 15% differenceamounts to another 6 hours of workproductivity lost per week. Although reducedwork productivity resulting from GIsymptoms amounts to approximately 15.8days per year for employees without IBS, itaccounts for more than 54.8 days per yearfor employees with IBS.
The largest component of total productivityreduction in employees with IBS wasimpairment while working. Absenteeismbecause of GI symptoms consistent with IBScontributed less to reductions in work productivityin this population. Absenteeismwas low among all participants—1.7% and0.4% among those with and without IBS,respectively (Figure 3), corresponding toapproximately 3 hours per month of absenceamong employees with IBS and less than1 hour per month of absence for non-IBSemployees. Although studies have reported higher average absenteeism rates of 1to 2 days per month, they have assessedabsenteeism from all causes, not just GIsymptoms.9,25
The impact of IBS on absenteeism andpresenteeism observed in this study mayimpose a substantial financial burden onemployers. It is possible that this study hasunderestimated the work productivity loss—a previous study using objective measures ofproductivity among employees from a largeUS credit card company found that meantotal time lost per month from presenteeism,absenteeism, and disability for employeeswith digestive disorders was equivalent tomore than twice the hours per month ofwork productivity loss measured in the presentstudy.26 Few data are available to comparesubjective (self-report) and objectivemeasures of productivity, but the validationstudies of the Work Limitations Questionnaireand the WPAI suggest that estimatesbased on self-reported data are valid.15,27
Our findings on overall work impairmentin employees with IBS (21%) are comparablewith those previously reported for other GIdisorders, such as GERD (16%-35%).19,20Overall work impairment was also comparablewith that for other health conditions,including chronic hand dermatitis (17%)18and allergic rhinitis (23%-42%),28 in studiesthat used the WPAI.
Employees with IBS had SF-36 scoreswithin the range of scores reported for otherlong-term health conditions, such as backpain, ulcer, osteoarthritis, and congestiveheart failure,29 and were comparable withprevious measurements of health-relatedQOL in IBS populations.3-5
There are limitations to this observationalstudy. As with all surveys, there is a riskfor selection bias, particularly given the 22%response rate. Although low, this responserate is consistent with rates seen in otheremployer-based studies (20%-50%).30-34 Thestudy cover letter sent to employees indicatedthat the study dealt with GI symptoms, adisclosure required by the employer and theinstitutional review board. It is possible thatemployees with symptoms were more likelyto participate, leading to an overrepresentationof IBS patients in the study population.The similarity between employees with andwithout IBS along demographic and workrelatedvariables suggests that study resultswere unlikely to have been biased by differencesin these variables. The banking industryemploys a disproportionate number ofwomen, but the ratio of women to men withIBS in our study was approximately 1.5:1—similar to proportions observed in other epidemiologicstudies of IBS.25,35,36 Additionally,treatment for IBS symptoms may influencethe degree of reduced work productivity.However, we were unable to explore the percentagesof reduced work productivityamong IBS patients being treated comparedwith those who had not sought care, becausewe did not question employees regardingtheir current treatments.
Our results indicate that IBS significantlyaffects work productivity. Further studiesare required to better assess this impactin more defined populations of IBS, such asthose seeking or receiving medical care,and in other employed populations. Inaddition, there is a need to better understandthe determinants of work productivitylosses in IBS and the relationshipbetween direct medical costs and indirectcosts (absenteeism and presenteeism).Finally, from an employer's perspective,additional efforts are needed to ensure thatpatients are identified and offered appropriatetreatment because unique therapeuticagents can decrease symptom severity andfrequency while improving employeehealth-related QOL and work productivity.Such efforts could pay dividends in theform of improved productivity and reducedabsenteeism.
1. Kay L, Jorgensen T, Jensen KH. The epidemiology ofirritable bowel syndrome in a random population: prevalence,incidence, natural history and risk factors. 1994;236:23-30.
2. Talley NJ, Weaver AL, Zinsmeister AR, Melton LJ3rd. Onset and disappearance of gastrointestinal symptomsand functional gastrointestinal disorders. 1992;136:165-177.
Ann Intern Med.
3. Creed F, Ratcliffe J, Fernandez L, et al. Health-relatedquality of life and health care costs in severe, refractoryirritable bowel syndrome. 2001;134:860-868.
4. Gralnek IM, Hays RD, Kilbourne A, Naliboff B,Mayer EA. The impact of irritable bowel syndrome onhealth-related quality of life. 2000;119:654-660.
Dig Dis Sci.
5. Whitehead WE, Burnett CK, Cook EW 3rd, Taub E.Impact of irritable bowel syndrome on quality of life.1996;41:2248-2253.
6. Frank L, Kleinman L, Rentz A, Ciesla G, Kim JJ,Zacker C. Health-related quality of life associated withirritable bowel syndrome: comparison with other chronicdiseases. 2002;24:675-689.
7. Talley NJ, Gabriel SE, Harmsen WS, Zinsmeister AR,Evans RW. Medical costs in community subjects withirritable bowel syndrome. 1995;109:1736-1741.
Arch Intern Med.
8. Leong SA, Barghout V, Birnbaum HG, et al. The economicconsequences of irritable bowel syndrome: a USemployer perspective. 2003;163:929-935.
Aliment Pharmacol Ther.
9. Hahn BA, Kirchdoerfer LJ, Fullerton S, Mayer E.Patient-perceived severity of irritable bowel syndrome inrelation to symptoms, health resource utilization andquality of life. 1997;11:553-559.
10. Hahn BA, Yan S, Strassels S. Impact of irritablebowel syndrome on quality of life and resource use inthe United States and United Kingdom. 1999;60:77-81.
11. Drossman DA. The functional gastrointestinal disordersand the Rome II process. 1999;45(suppl 2):II1-II5.
12. Thompson WG, Longstreth GF, Drossman DA,Heaton KW, Irvine EJ, Muller-Lissner SA. Functionalbowel disorders and functional abdominal pain. 1999;45(suppl 2):II43-II47.
Rome II: The
Functional Gastrointestinal Disorders.
13. Thompson WG, Longstreth GF, Drossman DA,Heaton K, Irvine EJ, Muller-Lissner S. 2nd ed. McLean,Va: Degnon Associates; 2000.
Am J Gastroenterol.
14. Brandt LJ, Bjorkman D, Fennerty MB, et al.Systematic review on the management of irritable bowelsyndrome in North America. 2002;97(suppl):S7-S26.
15. Reilly MC, Zbrozek AS, Dukes EM. The validity andreproducibility of a work productivity and activity impairmentinstrument. 1993;4:353-365.
Aliment Pharmacol Ther.
16. Reilly MC, Bracco A, Ricci JF, Santoro J, Stevens T.The validity and accuracy of the Work Productivity andActivity Impairment questionnaire—irritable bowel syndromeversion (WPAI:IBS). 2004;20:459-467.
Allergy Asthma Proc.
17. Murray JJ, Nathan RA, Bronsky EA, Olufade AO,Chapman D, Kramer B. Comprehensive evaluation ofcetirizine in the management of seasonal allergic rhinitis:impact on symptoms, quality of life, productivity, andactivity impairment. 2002;23:391-398.
J Am Acad Dermatol.
18. Reilly MC, Lavin PT, Kahler KH, Pariser DM.Validation of the Dermatology Life Quality Index andthe Work Productivity and Activity Impairment-ChronicHand Dermatitis questionnaire in chronic hand dermatitis.2003;48:128-130.
Am J Gastroenterol.
19. Wahlqvist P. Symptoms of gastroesophageal refluxdisease, perceived productivity, and health-related qualityof life. 2001;96(suppl):S57-S61.
20. Wahlqvist P, Carlsson J, Stalhammar NO, Wiklund I.Validity of a Work Productivity and Activity Impairmentquestionnaire for patients with symptoms of gastroesophagealreflux disease (WPAI-GERD): results from across-sectional study. 2002;5:106-113.
21. McHorney CA, Ware JE Jr, Raczek AE. The MOS36-Item Short-Form Health Survey (SF-36), II: psychometricand clinical tests of validity in measuring physical andmental health constructs. 1993;31:247-263.
22. Ware JE Jr, Sherbourne CD. The MOS 36-ItemShort-Form Health Survey (SF-36), I: conceptual frameworkand item selection. 1992;30:473-483.
N Z J Public Health.
23. Bensoussan A, Chang SW, Menzies RG, Talley NJ.Application of the general health status questionnaireSF36 to patients with gastrointestinal dysfunction: initialvalidation and validation as a measure of change. 2001;25:71-77.
24. Ware JE Jr, Kosinski M, Bayliss MS, McHorney CA,Rogers WH, Raczek A. Comparison of methods for thescoring and statistical analysis of SF-36 health profileand summary measures: summary of results from theMedical Outcomes Study. 1995;33(suppl):AS264-AS279.
25. Drossman DA, Li Z, Andruzzi E, et al. U.S. householdersurvey of functional gastrointestinal disorders:prevalence, sociodemography, and health impact. 1993;38:1569-1580.
J Occup Environ Med.
26. Burton WN, Conti DJ, Chen CY, Schultz AB,Edington DW. The role of health risk factors and diseaseon worker productivity. 1999;41:863-877.
27. Lerner D, Amick BC 3rd, Rogers WH, Malspeis S,Bungay K, Cynn D. The Work LimitationsQuestionnaire. 2001;39:72-85.
Ann Allergy Asthma
28. Meltzer EO, Casale TB, Nathan RA, Thompson AK.Once-daily fexofenadine HCl improves quality of lifeand reduces work and activity impairment in patientswith seasonal allergic rhinitis. 1999;83:311-317.
SF-36 Physical & Mental
Health Summary Scales: A Manual for Users of Version
29. Ware JE Jr, Kosinski M. 2nd ed. Lincoln, RI: QualityMetric Incorporated;2001.
Dissertation Abstracts International
Section A: Humanities & Social Sciences.
30. Chang LA. Job satisfaction, dissatisfaction of Texasnewspaper reporters. 1999;59:3260.
International Section B: The Sciences & Engineering.
31. Miller-Burke JA. The impact of traumatic events andorganizational response. 1998;58:5177.
32. Productivity and quality in the USA today.1990;34:27-31.
33. Seiler RE, Sapp RW. Just how satisfied are accountantswith their jobs? 1979;60:18-21.
34. Industrial engineers describe productivity improvementefforts, identify obstacles to their success. 1983;15:84-88.
35. Talley NJ, Zinsmeister AR, Van Dyke C, Melton LJ3rd. Epidemiology of colonic symptoms and the irritablebowel syndrome. 1991;101:927-934.
36. Saito YA, Locke GR, Talley NJ, Zinsmeister AR, FettSL, Melton LJ 3rd. A comparison of the Rome andManning criteria for case identification in epidemiologicalinvestigations of irritable bowel syndrome. 2000;95:2816-2824.