Visual AbstractAbstract

Background and objectives To date, employment figures of kidney transplant recipients in Europe are inconsistent. Additionally, little is known about work functioning of employed kidney transplant recipients and work functioning trajectories before and after transplantation.

Design, setting, participants, & measurements Data from the ongoing TransplantLines Biobank and Cohort study and from community-dwelling employed adults were used. Health-related work functioning of kidney transplant recipients was assessed with the Work Role Functioning Questionnaire 2.0 and compared with potential kidney donors and community-dwelling employed adults.

Results We included 668 kidney transplant recipients of working age (59% men, age 51±11 years) at median 3 (interquartile range, 2–10) years after transplantation, 246 potential kidney donors of working age (43% men, age 53±9 years), and 553 community-dwelling employed adults (70% men, age 45±11 years). The proportion of employed kidney transplant recipients was lower compared with potential kidney donors (56% versus 79%). If employed, the work functioning score of kidney transplant recipients was slightly lower compared with employed potential kidney donors yet higher compared with community-dwelling employed adults (medians 91 [interquartile range, 76–98], 94 [interquartile range, 85–99], and 88 [interquartile range, 79–95], respectively). Backward linear regression analyses revealed that lower educational level, having a kidney from a deceased donor, presence of tingling or numbness of hands or feet, presence of concentration/memory problems, presence of anxiety, and presence of severe fatigue were independently associated with lower work functioning among kidney transplant recipients. Additional subgroup analyses showed that work functioning scores were lower before transplantation than at 12 months after transplantation (83 [interquartile range, 66–93] versus 92 [interquartile range, 88–98], respectively; P=0.002).

Conclusions Stable employed kidney transplant recipients report to function well at work. In addition, this study shows that self-reported work functioning is higher after successful kidney transplantation compared with before transplantation.

Clinical Trial registry name and registration number: TransplantLines Biobank and Cohort study, NCT03272841

Introduction

Work is important because it provides income, but also, work provides social contacts, day filling and structure, and social status. Work therefore importantly contributes to quality of life (1⇓⇓–4). Although the proportion of employed kidney transplant recipients is generally considered relatively low, employment figures of stable kidney transplant recipients in Europe are inconsistent, with reported percentages ranging from 21% to 71% (5,6). In addition, little is known about work functioning among employed kidney transplant recipients. It is important to gain more insight into this topic because low work functioning could result in sickness absence, work disability, and unemployment (7⇓⇓–10).

Work functioning is a concept at the intersection of a person’s health and work performance. It reflects the ability of a person to meet work demands given a mental or physical health state, and it goes beyond the simple dichotomy of working or not working by assessing experiences in the work role (11⇓⇓⇓–15). We hypothesized that work functioning is lower among kidney transplant recipients compared with the general working population due to the potential negative effect of their vulnerable health status together with common neurologic and mental side effects of drugs and the high prevalence of severe fatigue in this population (16⇓–18). To date, it is unknown whether these factors are indeed associated with work functioning limitations in kidney transplant recipients. Identification of potential determinants is important to develop targeted interventions to improve work functioning of kidney transplant recipients and to help them stay at work.

Besides the individual perspective, being employed and being able to function well at work are important from societal and economic perspectives. After all, the majority of patients with kidney failure of working age receive a kidney transplant in Europe, and the number of kidney transplant recipients will likely continue to increase worldwide in the next decades (19,20). Improving work functioning can therefore help save societal costs for work disability and save costs for sickness absence and at-work productivity loss (8).

In this study, we therefore aimed to investigate the proportion of employed kidney transplant recipients in comparison with controls. In addition, we assessed work functioning among employed kidney transplant recipients in comparison with controls and aimed to identify potential work-related and clinical targets to improve work functioning of kidney transplant recipients. Finally, we investigated the trajectory of work functioning before and after transplantation.

Materials and MethodsStudy Design

Data from the ongoing, prospective TransplantLines Biobank and Cohort study, collected between June 2015 and May 2021 at the University Medical Center Groningen (UMCG) in The Netherlands, were used (21). All adult solid organ transplant recipients and donors were invited to participate. The study was approved by the Medical Ethics Review Board of UMCG (METc 2014/077) and adheres to the UMCG Biobank Regulation. The participation rate of this cohort was 81%, and 80% of the included participants filled in the Work Role Functioning Questionnaire (WRFQ). We included kidney transplant recipients with a functioning allograft approximately 1 year or longer after transplantation and potential kidney donors, who served as controls in the first comparator group. For the second comparator group, data from a previously published external dataset of community-dwelling employed adults were used (12). Participants were recruited from several companies and organizations in diverse work settings in The Netherlands via multiple approaches. All participants provided written informed consent on enrollment. The clinical and research activities being reported are consistent with the Principles of the Declaration of Istanbul as outlined in the Declaration of Istanbul on Organ Trafficking and Transplant Tourism and the World Medical Association Declaration of Helsinki.

Employment Status and Work Functioning

Work-related data were obtained by self-formulated questions. Work functioning was measured using the validated WRFQ version 2.0 (12). The 27-item WRFQ measures the extent to which physical and emotional problems affected the ability to perform the work role in the past 4 weeks for a broad variety of work demands. Response options range on a five-point Likert scale. There was also an answer option of “does not apply to my job.” Scores were calculated by taking the mean of the answers ×25, resulting in a percentage between zero and 100, which is the percentage persons can fulfill their work role in a week; a higher score therefore indicates better work functioning. The answer “does not apply to my job” was coded as missing. The score for a (sub-)scale was set to missing if >20% of the answers were missing (12,13).

Patient-Reported Outcome Measures

Side effects of immunosuppressive therapy were assessed using the Modified Transplant Symptom Occurrence and Symptom Distress Scale 59 Revised Questionnaire, of which all neurologic- and mental-related side effects were selected (17). Side effects were reported as present when participants experience the side effect regularly, almost always, or always. Fatigue was measured with the Checklist Individual Strength 20 Revised Questionnaire (22,23). A score ≥35 on the subscale “fatigue severity” was indicative of severe fatigue (23).

Other Variables

Clinical data were extracted from electronic patient records. Medication use was verified in a visit in which anthropometric measurements were also performed (21). Body mass index was calculated by dividing body weight by height squared. Laboratory parameters were measured using routine laboratory methods. The eGFR was calculated with the Chronic Kidney Disease Epidemiology Collaboration equation (24). Diabetes mellitus was defined according to the criteria of the American Diabetes Association, and anemia was defined according to the criteria of the World Health Organization (25,26). Educational level was assessed by questionnaires asking for the highest degree of education and was categorized as low (level 0, 1, or 2), moderate (level 3 or 4), or high (level 5 or 6) according to the International Standard Classification of Education (27).

Statistical Analyses

Data distribution was visually assessed using quantile-quantile plots and histograms. Normally distributed data were presented as mean±SD, non-normally distributed data were presented as median (interquartile range [IQR]), and categorical data were presented as number (valid percentage). Differences in WRFQ scores between groups were assessed using Mann–Whitney U tests. Differences between repeated measurements of work functioning were assessed using Wilcoxon signed rank tests.

Linear regression analyses with work functioning (WRFQ total score) as the dependent variable were performed to assess potential associations with work-related and clinical variables. We tested for interactions with age, sex, and eGFR. To examine which variables were independently associated with work functioning, forward selection of baseline variables according to the preceding univariable linear regression analyses was performed (P for inclusion =0.20) and followed by stepwise backward linear regression analyses (P for exclusion =0.05).

Results of linear regression analyses are presented as adjusted differences, referring to the number of SDs a dependent variable differs per SD higher value of the independent variable, together with 95% confidence intervals. To meet the assumptions of linear regression analyses, the WRFQ total score was transformed using the formula log10(maximal score +1− WRFQ total score)x−1. Other variables were log2 transformed where necessary. All statistical analyses were performed using the Statistical Package for the Social Sciences, version 25.0 (IBM Corp., Armonk, NY). A two-sided P=0.05 was regarded as statistically significant in all analyses.

In sensitivity analyses, a comparison of the WRFQ total scores while not excluding scores of participants who answered “not applicable to my job” to >20% of the questions was performed. In addition, regression analyses were repeated with this alternative WRFQ total score.

ResultsSample Characteristics

WRFQ data were available for 930 of 1155 kidney transplant recipients, 327 of 406 potential kidney donors, and of 553 community-dwelling employed adults from a previously published external dataset. Kidney transplant recipients who filled in the questionnaires more frequently received a kidney from a living donor and were more frequently preemptively transplanted compared with kidney transplant recipients who did not fill in the questionnaires (Supplemental Table 1). No differences in sex, age, body mass index, and eGFR were observed. After exclusion of participants above the increasing retirement age (Supplemental Table 2) (n=336) and students (n=7), a total of 668 kidney transplant recipients, 246 potential kidney donors, and 553 community-dwelling employed adults remained (Figure 1). In total, 59% of the kidney transplant recipients was men, and mean age was 51±11 years. Median time after transplantation was 3 (IQR, 2–10) years, and mean eGFR was 53±18 ml/min per 1.73 m2. The prevalence of men was lower among potential kidney donors (43%) and higher among community-dwelling employed adults (70%). Mean age was higher among potential kidney donors (53±9 years) and lower among community-dwelling employed adults (45±11 years). The educational levels of kidney transplant recipients and potential kidney donors were comparable. Kidney transplant recipients more frequently had a low educational level compared with community-dwelling employed adults. More detailed characteristics are presented in Tables 1 and 2.

Figure 1.

Participants flow chart. WRFQ, Work Role Functioning Questionnaire.

Table 1.

Characteristics of kidney transplant recipients, potential kidney donors, and community-dwelling employed adults in The Netherlands

Table 2.

Characteristics and associations with work functioning of employed kidney transplant recipients

Employment Figures

Work-specific characteristics are presented in Supplemental Table 3. A total of 56% of the kidney transplant recipients were employed compared with 79% of the potential kidney donors. The proportions of employed kidney transplant recipients were 62% among men and 48% among women. Most employed kidney transplant recipients had a permanent contract (72%), worked >32 h/wk (58%), and had mentally demanding tasks (44%). Sickness absence at the time of inclusion was reported by 8% of employed kidney transplant recipients, and 17% of the employed kidney transplant recipients received a supplementary disability pension. Among the 295 unemployed kidney transplant recipients, 71% received a disability pension. Characteristics of kidney transplants recipients and potential kidney donors per employment status are presented in Supplemental Table 4.

Work Functioning

Characteristics of employed kidney transplant recipients for whom a WRFQ total score was available for primary analyses (n=316), for whom the WRFQ total score was set as missing because participants answered “not applicable to my job” to >20% of the questions (n=46), and without a WRFQ total score because of missing data (n=11) were very similar (Supplemental Table 5). The WRFQ total score of employed kidney transplant recipients was slightly lower compared with employed potential kidney donors (91 [IQR, 76–98] versus 94 [IQR, 85–99]; P=0.006) yet higher compared with community-dwelling employed adults (91 [IQR, 76–98] versus 88 [IQR, 79–95]; P=0.03). The WRFQ score indicates the percentage of time a participant can fulfill his or her work role. For instance, among kidney transplant recipients, the 75th percentile of the WRFQ was 76, which indicates that 75% of the employed kidney transplant recipients were able to fulfill their work role for ≥76% of their working time, translating to almost 4 days in a full workweek. Results for each separate question of the WRFQ are presented in Supplemental Table 6. According to previously published cutoff values (28), 24% of the kidney transplant recipients reported low work functioning, 23% of the kidney transplant recipients reported medium work functioning, and 53% of the kidney transplant recipients reported high work functioning.

Among kidney transplant recipients, work scheduling demands were met a median of 94% (IQR, 63%–100%) of the work time, output demands were met a median of 88% (IQR, 63%–100%) of the work time, physical demands were met a median of 100% (IQR, 88%–100%) of the work time, mental and social demands were met a median of 96% (IQR 82%–100%) of the work time, and flexibility demands were met a median of 95% (IQR 85%–100%) of the work time. Comparisons of these scores with scores of control groups are presented in Figure 2 and Supplemental Table 7.

Figure 2.

Differences in work functioning scores as assessed by the work role functioning questionnaire (WRFQ) between kidney transplant recipients, potential kidney donors, and community-dwelling employed adults. A lower score indicates worse work functioning. Differences between kidney transplant recipients and comparator groups were assessed using Mann–Whitney U tests.

Associations with Work Functioning in Employed Kidney Transplant Recipients

Working hours per week, working tasks, age, sex, and immunosuppressive drugs were not associated with work functioning (Table 2). Being moderately educated was more strongly positively associated with work functioning than being highly educated. β-blocker use was negatively associated with work functioning, just like almost all patient-reported outcome measures, of which severe fatigue showed the strongest negative association with work functioning followed by concentration/memory problems, restlessness/nervousness, muscle weakness, and depressive feelings. Backward linear regression analyses showed that lower educational level, having a kidney from a deceased donor, presence of tingling or numbness of hands or feet, presence of concentration/memory problems, presence of anxiety, and presence of severe fatigue were independently associated with lower work functioning.

Repeated Measurements of Work Functioning in Employed Kidney Transplant Recipients

Baseline characteristics of kidney transplant recipients for whom pretransplantation work functioning data were available were generally comparable with those for whom pretransplantation work functioning data were not available, with the exception of the proportion of preemptive transplantations, which was higher among the kidney transplant recipients for whom pretransplantation work functioning data were available (Supplemental Table 8). WRFQ total scores shortly before transplantation were lower than at 12 months after transplantation (83 [IQR, 66–93] versus 92 [IQR, 88–98], respectively; P=0.002; n=29), indicating that work functioning improves after transplantation (Figure 3). Among the 11 patients with the lowest WRFQ scores before transplantation, five patients were on dialysis at the time of filling in the questionnaire. In addition, among the ten patients for whom the WRFQ score decreased or did not change, nine had undergone a preemptive transplantation. Baseline characteristics of employed kidney transplant recipients with work functioning data at 12 and 24 months are presented in Supplemental Table 9. No difference in WRFQ total scores was found between 12 and 24 months after transplantation (90 [IQR, 78–95] versus 89 [IQR, 76–99]; P=1.0; n=56).

Figure 3.

Work Role Functioning Questionnaire total scores before and 12 months after transplantation of 29 employed kidney transplant recipients. Self-reported work functioning was higher after transplantation in the vast majority of kidney transplant recipients. Four patients reported lower work functioning after transplantation (more than five points lower) compared with before transplantation.

Sensitivity Analyses

Not excluding work functioning scores of participants who answered “not applicable to my job” to >20% of the questions, the 25th percentile of WRFQ total score of kidney transplant recipients was lower, but the median and 75th percentile remained similar (91 [IQR, 73–98]). In these analyses, the score of kidney transplant recipients was numerically lower when compared with potential kidney donors (94 [IQR, 85–99]; P=0.002) and numerically higher but statistically not different when compared with community-dwelling employed adults (88 [IQR, 79–95]; P=0.20). Results of univariable regression analyses were generally comparable. Backward regression analyses showed that lower educational level, presence of concentration/memory problems, and presence of severe fatigue were independently associated with lower work functioning, similar to the primary analyses (Supplemental Table 10).

Discussion

The proportion of employed stable kidney transplant recipients was 56%. Despite the prevalent side effects of immunosuppressive therapy and the high prevalence of fatigue, employed stable kidney transplant recipients report to function well at work. Educational level, donor type, tingling or numbness of hands or feet, concentration/memory problems, anxiety, and severe fatigue were independently associated with lower self-reported work functioning among kidney transplant recipients. Analyses in a subgroup of employed patients with kidney failure showed that self-reported work functioning was higher after successful kidney transplantation.

In 2007, a study showed that the proportion of employed Dutch kidney transplant recipients was 52% (29). Since then, general transplant care has improved (20). In addition, the proportion of preemptive transplantations has increased, which hypothetically results in fewer patients losing their jobs because of frequent dialysis, which greatly affects daily lives (30). Despite these improvements and the increased proportion of preemptive transplantations, the proportion of employed kidney transplant recipients has improved only slightly to 56% in this study. An explanation could be that some kidney transplant recipients changed their priorities after kidney transplantation and focused more on other things in life rather than work. Nevertheless, these study findings confirm that the proportion of employed kidney transplant recipients in The Netherlands is generally between 50% and 60%.

In extension of previous studies among kidney transplant recipients that only investigated dichotomous work outcomes, we additionally investigated self-reported work functioning in this population. This novel work outcome provides insight into how transplant recipients function at work, what barriers they experience, and how much time they are actually productive in their work time (12). Contrary to our expectations, self-reported work functioning among kidney transplant recipients was good in comparison with our control groups and with other populations, including shift workers; university workers; and patients with musculoskeletal pain, cancer, or endometriosis (13,31,32). This may have been achieved by alterations at work to create a good balance between working capacity and workload. An alternative explanation can be a response shift; recipients may compare their work functioning with the pretransplant period, in which they likely functioned worse at work because of the (treatment of) kidney failure, or they get used to their decreased work functioning (33). The results in our study are highly encouraging, and they demonstrate a clear message to employers that kidney transplant recipients can function very well at work. These findings can therefore help to reduce any stigmas regarding work and work functioning after kidney transplantation. It is important to note that the observed work functioning can only be determined for employed kidney transplant recipients, who were generally younger and healthier compared with the unemployed transplant recipients in our study. Work functioning may, therefore, be worse among unemployed kidney transplant recipients if they would get a job.

Results of regression analyses indicate that work functioning is multifactorial and that a combination of good physical and mental status is important to function well at work. Besides physical and mental health, job type also seems to influence work functioning, as educational level, which likely reflects the type of job, was also independently associated with work functioning. Weekly working hours, age, and use of specific immunosuppressive medication were not associated with work functioning. It must be noted that a large proportion of the work functioning values of kidney transplant recipients remains unexplained by the identified variables.

Strengths of this study are the use of a well-defined cohort with extensive data regarding clinical parameters, medication use, and health and functional outcomes. In addition, the availability of serial measurements in a subgroup of patients provided novel insights into the trajectories of work functioning after transplantation. However, there are limitations that we acknowledge. First, because of the observational study design, no conclusions regarding causal relationships can be drawn. Second, we could not exclude the possibility of a selection bias favoring healthier recipients. Indeed, kidney transplant recipients who filled in the questionnaires more frequently received a kidney from a living donor and were more frequently preemptively transplanted compared with those who did not fill in the questionnaires. However, we were able to include a large population of stable kidney transplant recipients in their working age and reached a high response rate to questionnaires (34). Third, no data were available on the causes of unemployment and on how many of the kidney transplant recipients were unemployed pretransplantation. Fourth, potential kidney donors may have personality and health characteristics that differ from the general population, making them less suitable as a comparator group. Fifth, repeated measurements were available in a subset of kidney transplant recipients, which increases the possibility of a selection and response bias in these analyses. Finally, this single-center study only included patients from the northern part of The Netherlands, which calls for prudence when extrapolating these findings to other areas.

In conclusion, the proportion of employed stable kidney transplant recipients is 56%. Stable employed kidney transplant recipients report to function very well at work. In addition, this study shows that self-reported work functioning is higher after successful kidney transplantation compared with before kidney transplantation.

Disclosures

C. Annema reports research funding from Chiesi Pharmaceuticals BV and the Dutch Kidney Foundation and serving in advisory or leadership roles for the Dutch Transplant Society and the European Transplant Allied Health Professionals Committee of the European Society for Organ Transplantation. S.J.L. Bakker reports research funding from Astellas Pharma and Chiesi Pharmaceuticals BV and an advisory or leadership role with the Dutch Health Council and the scientific board of the Dutch Kidney Foundation. S.P. Berger reports consultancy agreements with Novartis, research funding from Chiesi Pharmaceuticals BV and Novartis, honoraria from Astellas and Novartis, and advisory or leadership roles with the Dutch Transplant Foundation Supervisory Board and the Novartis Advisory Board. U. Bültmann reports an advisory or leadership role with Journal of Occupational Rehabilitation. G.J. Navis reports serving as the chair (up to December 2021) of the Scientific Board of the Dutch Kidney Foundation, a member of the Health Council of The Netherlands, and a member of the Permanent Advisory Board on Prevention of the Ministry of Health. All remaining authors have nothing to disclose.

Funding

This work was supported by Astellas grant TransplantLines Biobank and Cohort study and Chiesi Pharmaceuticals BV grant PA-SP/PRJ-2020-9136 and cofinanced by the Dutch Ministry of Economic Affairs and Climate Policy by means of the Public Private Partnership allowance made available by Top Sector Life Sciences & Health to stimulate public-private partnerships.

Author Contributions

S.J.L. Bakker, U. Bültmann, T.J. Knobbe, D. Kremer, and A. Visser conceptualized the study; F.I. Abma, C. Annema, S.J.L. Bakker, T.J. Knobbe, and D. Kremer were responsible for data curation; S.J.L. Bakker was responsible for investigation; T.J. Knobbe was responsible for formal analysis; F.I. Abma, S.J.L. Bakker, T.J. Knobbe, D. Kremer, and A. Visser were responsible for methodology; S.J.L. Bakker was responsible for project administration; F.I. Abma was responsible for validation; T.J. Knobbe was responsible for visualization; S.J.L. Bakker was responsible for funding acquisition; S.J.L. Bakker, U. Bültmann, and A. Visser provided supervision; T.J. Knobbe and D. Kremer wrote the original draft; and C. Annema, S.J.L. Bakker, S.P. Berger, U. Bültmann, G.J. Navis, S.F. van der Mei, and A. Visser reviewed and edited the manuscript.

Supplemental Material

This article contains supplemental material online at http://cjasn.asnjournals.org/lookup/suppl/doi:10.2215/CJN.05560522/-/DCSupplemental.

Supplemental Table 1. Characteristics of participants who filled in the questionnaire and participants who did not fill in the questionnaires.

Supplemental Table 2. Increasing retirement age in The Netherlands.

Supplemental Table 3. Work-specific characteristics of kidney transplant recipients, potential kidney donors, and community-dwelling employed adults.

Supplemental Table 4. Characteristics of kidney transplant recipients and potential kidney donors per employment status.

Supplemental Table 5. Characteristics of employed kidney transplant recipients for whom a WRFQ total score was available for primary analyses, for whom the WRFQ total score was set at missing because participants answered “not applicable to my job” to >20% of the questions, and without a WRFQ total score because of missing data.

Supplemental Table 6. Results per question of the Work Role Functioning Questionnaire 2.0 of 362 kidney transplant recipients.

Supplemental Table 7. Results for subscores and total scores of the Work Role Functioning Questionnaire 2.0 in kidney transplant recipients, potential kidney donors, and community-dwelling adults.

Supplemental Table 8. Characteristics of employed kidney transplant recipients for whom pretransplantation work functioning data were available and for whom pretransplant work functioning data were not available.

Supplemental Table 9. Characteristics and work functioning of kidney transplant recipients 12 and 24 months after transplantation.

Supplemental Table 10. Associations with work functioning of employed kidney transplant recipients, including work functioning total scores of participants who answered “not applicable to my job” to >20% of the questions.

Footnotes

Published online ahead of print. Publication date available at www.cjasn.org.

See related Patient Voice, “Dialysis, Transplantation, and Work: Honoring Original Intent,” on pages 1431–1432.

Received May 10, 2022.Accepted August 18, 2022.Copyright © 2022 by the American Society of Nephrology