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Reged: 12/09/02
Posts: 7677
Loc: Seattle, WA
Impairment in Work Productivity and Health-related Quality of Life in Patients With IBS
05/08/05 06:11 PM

Impairment in Work Productivity and Health-related Quality of Life in Patients With IBS

Bonnie B. Dean, PhD; Daniel Aguilar, MPH; Victoria Barghout, MSPH; Kristijan H. Kahler, SM; Feride Frech, MPH; David Groves, PhD; and Joshua J. Ofman, MD

Irritable bowel syndrome (IBS) is a long-term and episodic medical disorder shown to have an impact on work productivity and health-related quality of life (QOL). The objective of this study was to assess the impact of IBS on work productivity and on health-related QOL in an employed population in the United States and to quantify the cost of these factors to the employer. A 2-phase survey was sent to the workforce of a large US bank to assess the presence of IBS among employees and to measure their work productivity (absenteeism [time lost from work] and presenteeism [reduced productivity at work]) and health-related QOL. Forty-one percent of the 1776 employees responding to both phases of the survey met the Rome II criteria for IBS. Employees with IBS reported a 15% greater loss in work productivity because of gastrointestinal symptoms than employees without IBS and had significantly lower Medical Outcomes Study Short Form 36 (SF-36) scores than those without IBS. IBS was associated with a 21% reduction in work productivity, equivalent to working less than 4 days in a 5-day workweek. Employees with IBS also had significantly lower scores on all domains of the SF-36, indicating poorer functional outcomes. Reduced work productivity and diminished QOL of these magnitudes may have substantial financial impact on employers.

(Am J Manag Care. 2005;11:S17-S26)

Patients with irritable bowel syndrome (IBS) report symptoms that may wax and wane in type and severity over time1,2 and that can have a negative impact on health-related quality of life (QOL).3-6 IBS affects adults of all ages, primarily those of working age (30-50 years old).2 In the United States, an estimated 10% to 20% of adults are believed to have symptoms consistent with this disorder.3

Although estimates of the direct costs associated with IBS are staggering and can vary 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 concern to employers in the United States, who rely heavily on a healthy workforce and who contract with health plans and other payers to cover the healthcare costs of their employees. For these reasons, employers often implement wellness and disease management programs to optimize workforce health.

Leong and colleagues8 studied healthcare insurance data of the employees of a self-insured Fortune 100 company and determined that direct and indirect costs for patients with IBS were substantially greater than those for a matched non-IBS control group. In 1998, the direct and indirect medical costs to the employer for 1 employee with IBS were $3997 and $2367, respectively, which were $1651 and $468 greater than the direct and indirect medical costs for 1 employee without IBS. The indirect cost for patients with IBS is likely to have been underestimated, however, because this estimate included absenteeism but not presenteeism.

Hahn and colleagues9 measured the impact of IBS on absenteeism. Although the actual number of hours employees were absent from work because of IBS was not substantial, the number of missed workdays increased significantly as the severity of illness increased. In a separate study of IBS patients, Hahn and colleagues10 found that Medical Outcomes Study Short Form 36 (SF-36) scores of respondents from the United States and the United Kingdom were significantly lower, meaning that they were worse than the respective population norms. Moreover, 30% of US respondents missed at least 1 full day of work in the 4 weeks preceding the survey, and 46% reported "cutting back" on some workdays because of IBS.

Although several studies have reported reduced health-related QOL in IBS populations, 3-6 limited research has been conducted to assess health-related QOL or absenteeism in an employed population with IBS, and even less research has been conducted to quantify the economic impact of these factors on the employer. Additionally, these studies have largely ignored the specific impact of IBS-associated gastrointestinal (GI) symptoms on presenteeism.

Our objective was to assess the impact of IBS on work productivity (presenteeism and absenteeism) and on health-related QOL in a US employed population and to quantify the cost of these factors to the employer.


Participants were employees of Comerica Incorporated, a nationwide bank with major branches in multiple states (Michigan, California, Texas, and Florida). From April 2002 to August 2002, all employees of Comerica (N = 11 806) were invited to participate in a 2-phase survey regarding GI health and related symptoms.

All Comerica employees were mailed a survey designed to (1) identify those with IBS (including subgroup classification for constipation [IBS-C] or diarrhea [IBS-D]) using the Rome II criteria11-13; (2) measure the frequency, severity, and bothersomeness of IBS symptoms; and (3) capture information on sociodemographics, long-term health conditions (including physician-diagnosed IBS), and job characteristics. A postcard was included in the initial mailing to request signed consent for participation in the followup survey. Employees who completed initial surveys and consent forms received a second survey measuring work productivity loss because of IBS and assessing QOL (Figure 1). The Cedars-Sinai Health System Institutional Review Board approved this study.

Names of initial survey participants were entered in a raffle for 1 of 9 gift checks valued between $100 and $500. Second-phase survey participants received a gift check for $25. All participants received educational material regarding IBS at the conclusion of the study.

Rome II Criteria. Employees were administered the Rome II diagnostic criteria questionnaire11-13 to assess the presence of IBS. According to the Rome II criteria, IBS is defined by the presence of abdominal discomfort or pain for at least 12 weeks, which need not be consecutive, during the preceding 12 months, and the discomfort or pain should have 2 of the following 3 features: it should be relieved with defecation; its onset should be associated with a change in the frequency of the stool; its onset should be associated with a change in the form (appearance) of the stool.13 Supportive symptoms can be used to classify IBS patients into symptom subgroups: IBS-C, characterized by less than 3 stools per week, hard/lumpy stools, straining, and feeling of incomplete bowel evacuation; IBS-D, characterized by more than 3 stools per week, loose or watery stools, and urgency; and mixed-pattern subtypes (alternating IBS).13,14

Assessment of Work Productivity. Work productivity was measured using the Work Productivity and Activity Impairment (WPAI) questionnaire,15 which was developed and validated as a general health measure that can be easily modified for specific health conditions. Adapted versions of the WPAI16 have been developed for use in patients with conditions such as allergy,16,17 long-term hand dermatitis,18 and gastroesophageal reflux disease (GERD).19,20 We adapted the WPAI to estimate the impact of GI symptoms consistent with IBS, including abdominal pain or discomfort, bloating, and constipation or diarrhea, on work productivity.16 Areas assessed included level of impairment during work and other daily activities and hours absent from work because of IBS symptoms during the previous 7 days. A scale from 0 to 10 was used to assess the degree to which GI symptoms consistent with IBS negatively affected a patient's productivity while working and to assess how they affected daily activity. Measures of productivity and absenteeism were combined in the work productivity score (WPS), which quantifies reduced work productivity (absenteeism and presenteeism) attributed to GI symptoms consistent with IBS as a percentage of potential total work productivity during a full-time workweek. The WPS was calculated as follows:

WPAI measures are interpreted as a percentage reduction in productivity (or a percentage of productivity lost) and are adjusted for part-time status. For example, a WPS of 5% indicates that a full-time employee is working at only 95% of full work potential (eg, 40 hours) because of reductions associated with absenteeism and presenteeism. A WPS of 5% for an employee working 40 hours per week would imply a reduction of 2 hours of potential work productivity lost.

Medical Outcomes Study Short Form. QOL was assessed using the SF-36 questionnaire, a generic instrument designed to measure overall health status.21,22 The WPS = [(hours absent from work + percentage of reduced productivity at work hours actually worked)/(hours missed because of ill health + hours worked)] 100. SF-36, which has previously been validated for use in the measurement of health-related QOL among IBS patients,23 assesses health status across 8 subscales, including physical functioning, physical role limitations, emotional role limitations, social functioning, bodily pain, general mental health, vitality, and general health perceptions. Additionally, subscale scores can be collapsed into 2 summary scores, the mental component summary (MCS) and the physical component summary (PCS).24 Scores for each subscale and summary score range from 0 (poor health) to 100 (optimal health).

Statistical Analysis. Employees meeting the Rome II criteria for IBS were compared with those not meeting the criteria with respect to a variety of variables, including demographic and work-related measures, presence of comorbid conditions, and history of hysterectomy or surgeries of the GI tract. Chi-square tests were used for categorical variables and t tests for continuous variables. Two-sided P values were calculated, and statistical significance was set at the κ= 0.05 level.

The kappa coefficient was calculated to assess the agreement between respondents meeting the Rome II criteria (based on the questionnaire) and respondents indicating a diagnosis of IBS by a physician or another medical professional (formal diagnosis). The kappa statistic describes the degree of agreement between 2 variables. Kappa values range between -1.0 (perfect disagreement) and +1.0 (perfect agreement), with zero indicating agreement that is completely accounted for by chance. Values of 0.0 to 0.2 indicate slight agreement, 0.2 to 0.4 fair agreement, 0.4 to 0.6 moderate agreement, 0.6 to 0.8 substantial agreement, and 0.8 to 1.0 near-perfect agreement.

Employees with and without IBS (as determined by their having met the Rome II criteria) were compared with respect to mean percentage reductions across WPAI measures of productivity, and a similar comparison was made between IBS-C and IBS-D subgroups. A nonparametric method, bootstrapping, was used to estimate the 95% confidence interval (CI) for differences in productivity impairments. Bootstrapping is a statistical approach for estimating CIs from data simulations when distributions deviate considerably from the assumptions of parametric statistics. Mean percentage reductions in WPAI measures of productivity were converted to lost work productivity based on total number of hours absent from work (absenteeism) and total number of hours at reduced productivity while at work (presenteeism) based on a 40-hour workweek (using the WPS formula presented in this article). These hours were also quantified based on the mean salary and mean wages of employees in the sample. The mean cost in dollars of reduced work productivity (absenteeism and presenteeism) per year (assuming full-time employment of 2080 hours of potential work time annually per employee) because of GI symptoms consistent with IBS was calculated as the difference in cost of reduced work productivity between employees with and without IBS. The cost per employee was extrapolated to a company with 10 000 employees assuming IBS prevalence estimates ranging from 10% to 20%.

Health-related QOL scores were calculated for the MCS and PCS and for each of the 8 SF-36 subscales. Mean differences in scores between IBS and non-IBS groups and between IBS-C and IBS-D subgroups were calculated with 95% CI.


Survey participation is outlined in Figure 1. The initial survey was sent to all 11 806