Self-reported work ability in long-term breast cancer survivors. A population-based questionnaire study in Denmark

Abstract

Background. Although up to 80% of women can return to work after treatment for breast cancer, maintaining an affiliation to the labour market may be a challenge, as shown by the fact that the risks for unemployment and early retirement are increased in the years after treatment of cancer. It is important to understand the work problems experienced by cancer survivors, including their ability to work. The aim of this study was to determine whether the ability of long-term breast cancer survivors to work was different from that of a cancer-free control group. Material and methods. In this population-based cross-sectional questionnaire study, 776 breast cancer survivors were matched with 1552 cancer-free women. Women with breast cancer diagnosed in 1997–2000 were identified in the Danish Cancer Registry, and the cancer-free controls were sampled from the Central Population Registry. Work ability was measured from a single question on the ‘work ability index’. Furthermore, the questionnaire contained questions on socioeconomic factors, health-related factors and factors related to the workplace. Results. The overall response rate was 57% (493 survivors and 830 controls). After exclusions, the study population consisted of 170 survivors and 391 controls. Women with a diagnosis of breast cancer who had survived at least five years and had returned to work reported significantly poorer work ability than cancer-free controls. In models with adjustment for socioeconomic factors, health-related factors and support at work, the factors most strongly associated with impaired work ability were low income, fatigue and little help and support from a supervisor. Conclusion. Our findings indicate that the work ability of long-term breast cancer survivors who are disease-free and back in work is impaired in comparison with that of cancer-free women.

A return to work after cancer treatment represents a transition from patient to normality. Although 30–50% of breast cancer survivors report persisting pain after three to five years [1], up to 80% are usually able to continue working after treatment [2,3]. In subsequent years, however, maintaining an affiliation to the labour market may be a challenge for cancer survivors, as indicated by the finding that the risks for unemployment and early retirement are increased in the years after cancer treatment [4–8]. It is important to understand the mechanisms behind any problems experienced by cancer survivors at work. One such problem is reduced work ability [9].

‘Work ability’ is a multidimensional phenomenon. It has been defined as workers’ ability to do their work according to the demands of the job as well as their health and mental resources [10]. It is usually measured on the ‘work ability index’, which includes scales for physical and mental work ability and a single question about general work ability. The single-item question has been shown to be a good alternative to the total work ability index questionnaire [11] because it captures not only mental and physical work ability but also a global weighting of perceived work ability with regard to personal resources and work demands.

Perceived work ability among survivors of cancers at different sites was measured in a study in Finland, in which 19% of the survivors reported that their mental work ability was reduced and 26% that their physical work ability was poorer due to their cancer [12]. The work ability scores were not, however, different from those of a cancer-free control group. This finding is in contrast to those of other studies, in which the work ability of breast cancer survivors was lower than that of cancer-free groups [2,13]. As work ability is a complex concept, it might change over time as a new balance between job demands and personal capacity is established. de Boer et al. found that work ability increased with time after cancer treatment and was a strong predictor of resuming work after cancer [14].

In the general population, work ability is associated with almost all the factors of work life, whether related to the individual (health, functional capacity, age, marital status, education and occupation), to the workplace (physical and mental workload, organisation) or to the social environment and society [15]. It is not known, however, whether this association also holds for long-term breast cancer survivors.

The aim of this study was to determine whether the work ability of long-term breast cancer survivors was different from that of a cancer-free control group. Further, we investigated whether socioeconomic factors (education, occupation and income), health-related factors (fatigue, anxiety and depression) and workplace factors (support and promotion) were associated with work ability.

Material and methods

Study population

We conducted a population-based, cross-sectional, questionnaire study of breast cancer survivors and a matched reference group. The study is part of a Nordic collaboration on the work situation of cancer survivors in the Nordic countries, the Nordic Study Group of Cancer and Work Life. Women with invasive localised breast cancer (ICD-10: 170) diagnosed in 1997–2000 were identified in the Danish Cancer Registry, in which all incident cases of cancer in Denmark have been registered since 1943 by cross-linkage to death certificates and to the national Hospital Discharge Registry. The completeness of the Cancer Registry for breast cancer is approximately 99% [16]. Women were included if they were of working age at the time of diagnosis (30–60 years), treated at one of three selected hospitals in Denmark and alive on 1 October 2005. Permission to contact the breast cancer survivors was obtained from the ward in which they were treated.

Controls were sampled from the Central Population Registry from among all Danish women who were alive on 1 October 2005. Oversampling was done in order to exclude women registered in the Cancer Registry. The cancer-free controls were then matched by date of birth and neighbourhood of residence, at a ratio of two controls to one case.

A questionnaire, an invitation letter and a consent form were mailed to the women selected. If the questionnaire was not returned within two weeks, a reminder was sent; another reminder was sent after four weeks. Women who did not respond to the two written reminders were contacted by telephone if the telephone number could be identified.

In all, the questionnaire was sent to 2328 women—776 breast cancer survivors and 1552 matched controls—and was returned by 1323 (Figure 1). We excluded 496 women (190 breast cancer survivors and 306 cancer-free women) because they were not part of the workforce at the time of inclusion. We obtained information on clinical prognostic factors and on any recurrence of breast cancer from the Danish Breast Cancer Group, which has registered breast cancer patients since 1977 and contains information on 95% of Danish women under 75 years of age with breast cancer diagnosed during that period [17]. On the basis of the clinical data, we excluded breast cancer survivors who had experienced a recurrence of their breast cancer before filling in the questionnaire (N = 28) in order to obtain a group of survivors with a reasonable prognosis and ability to hold a job. After further exclusion of 235 participants for whom answers on core variables were missing and who were over 64 years (N = 3), the study population comprised 561 women: 170 breast cancer survivors and 391 cancer-free controls.

Figure 1. Flowchart showing inclusion of women in the study.

Information on work ability and workplace variables

Work ability was measured from answers to the single question: ‘Assume that your work ability at its best has a value of 10 points. How many points would you give your current work ability? (0 means that you cannot work at all).’ In order to obtain higher statistical power, the outcome was dichotomised as high (score 9–10) versus low (score ≤ 8) on the basis of the lowest quartile rated by the cancer survivors.

The psychosocial work environment was measured from the answers to five questions regarding their colleagues and closest supervisor from the validated General Nordic Questionnaire [18]: ‘If you need it, is it then possible to get help and support from colleagues/closest supervisor?’ (two questions), ‘If you need it, are your colleagues/closest supervisor willing to listen if you have work-related problems?’ (two questions) and ‘Is your work valued by your closest supervisor?’ The scores for the five questions ranged from 1 (very seldom) to 5 (very often). On the basis of the distribution of answers, they were subsequently dichotomised to ‘very seldom/seldom’ and ‘sometimes/often/very often’. Promotion and job improvements were measured from answers to the question: ‘Has your position at work improved (with, e.g. promotion or personal increment) during the last eight years?’, grouped into ‘yes’ and ‘no/not possible’.

Information on socioeconomic and health-related variables

We used the answers to three questions to define socioeconomic position: highest attained educational level, job type and household income. Educational level was grouped as (1) primary school, high-school and vocational education and (2) higher education. Job type was dichotomised into supervisor/academic/managerial or skilled/unskilled worker, and household income was defined from mean reported income grouped into low (first quartile), medium (second and third quartiles) and high (fourth quartile).

The health-related characteristics we measured were fatigue, depression and anxiety. Fatigue was defined from answers to the question: ‘How often have you felt unusual tiredness?’ and grouped into often (very often/often/sometimes) and seldom (seldom/never). Depression and anxiety were measured on the Hospital Anxiety and Depression Scale [19], in which each of seven items on depression and seven on anxiety is rated on a scale of 0 (not at all) to 3 (very much). The scores for each of the two subscales are constructed by simple summation of the seven items to obtain separate scores for anxiety, depression and a global measure. As recommended, we used a cut-off of 7 on the scales, whereby a score ≤ 7 indicated anxiety and depression and scores < 7 were grouped as no anxiety or depression [20].

Statistical analyses

Descriptive data on breast cancer survivors and cancer-free controls were compared with χ²-tests for all categorical variables and t-tests for continuous variables. Multiple logistic regressions analyses for poor work ability were conducted for all covariates. The associations between work ability and the covariates were expressed as odds ratios (ORs), with 95% confidence intervals (CIs). We used two models, the first with adjustment for age and the other further adjusted for socioeconomic, health-related and workplace variables. Age was entered as a continuous variable. For the categorical variables, the category with the best prognosis for work ability in the control group was chosen as the reference group.

Data handling and statistical analyses were performed with SAS statistical software 9.1.

Results

Questionnaires were returned by 493 survivors (64%) and 830 cancer-free controls (53%), giving a response rate of 57% (Figure 1). The breast cancer survivors were significantly older than cancer-free women (p = 0.001), had a lower income (p = 0.03) and more frequently reported lack of support from colleagues and supervisors (Table I). Cancer survivors rated their work ability (mean, 8.66) significantly lower than the cancer-free controls (mean, 8.89) (p < 0.0001). Health-related characteristics did not differ between the two groups.

Table I. Descriptive characteristics of 170 breast cancer survivors and 391 cancer-free controls.

	Survivors N (%)	Controls N (%)	p*
Socioeconomic characteristics
Age (years)
35–44	11 (6)	48 (12)
45–54	72 (42)	191 (49)
55–64	87 (51)	152 (39	0.001
Mean (range)	54.2 (42–64)	52.4 (37–64)	0.0004
Highest attained educational level
Primary or high-school/vocational	143 (84)	339 (87)
Higher	27 (16)	52 (13)	0.35
Job type
Supervisor/academic/managerial	86 (51)	200 (51)
Skilled/unskilled/other	84 (49)	191 (49)	0.92
Income (Danish kr per year)
Low	63 (37)	98(25)
Medium	76 (44)	203 (52)
High	31 (19)	90 (23)	0.02
Mean	529 (775)	582 (181)	0.03
Health-related characteristics
Fatigue
Often	29 (17)	45 (11)
Seldom	141 (83)	346 (89)	0.08
Anxiety (HADS) (score)
≥ 7	60 (35)	122 (31)
< 7	110 (65)	269 (69)	0.38
Depression (HADS) (score)
≥ 7	15 (9)	22 (6)
< 7	155 (91)	369 (94)	0.17
Support at work
Help and support from colleagues
Seldom/sometimes	37 (22)	57 (15)
Often	133 (78)	334 (85)	0.04
Help and support from supervisor
Seldom/sometimes	49 (28)	71 (18)
Often	121 (72)	320 (82)	0.01
Listened to by colleagues
Seldom/sometimes	35 (20)	47 (12)
Often	135 (80)	344 (88)	0.01
Listened to by supervisor
Seldom/sometimes	8 (5)	21 (5)
Often	162 (95)	370 (95)	0.73
Valued by supervisor
Seldom/sometimes	33 (19)	57 (15)
Often	137 (81)	334 (85)	0.17
Promotion
No/not possible	91 (53)	134 (34)
Yes	79 (47)	257 (66)	<.00001
Work ability (score)
≥ 8	66 (39)	113 (29)
< 8	104 (61)	278 (71)	< 0.02
Mean	8.66 (0–10)	8.89 (0–10)	< 0.0001

HADS, Hospital Anxiety and Depression Scale.

For discrete variables: χ²-test. For continuous variables: t-test.

Factors associated with reporting reduced work ability (score ≤ 8) are shown in Table II. In the model adjusted only for age, low education (OR 2.24; 95% CI 1.08–4.67) and low income (OR 3.81; 95% CI 1.86–7.78) were significant risk factors for reduced work ability among breast cancer survivors, whereas only low income was associated with a low work ability score in the cancer-free group (OR 2.14; 95% CI 1.11–4.14). For both groups, fatigue, anxiety and depression were all associated with reduced work ability; the association between fatigue and reduced work ability was, however, stronger among cancer survivors than among the controls. Poor support from colleagues and supervisors also increased the risk for rating impaired work ability. Cancer survivors who reported that they had not been promoted were more likely to perceive poor work ability than both the cancer-free controls and survivors who had been promoted.

Table II. Age-adjusted and mutually adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for impaired work ability among 170 breast cancer survivors and 391 cancer-free controls.

	Age-adjusted OR (95% CI)		Fully adjusted OR (95% CI)^1
	Survivors	Controls	Survivors	Controls
Socioeconomic characteristics
Highest attained educational level
Primary or high-school/vocational	2.24 (1.08–4.67)	1.38 (0.69–2.74)	1.17 (0.50–2.74)	0.92 (0.41–2.03)
Higher	1.08 (0.36–3.21)	1	0.59 (0.16–2.15)	1
Job type
Supervisor/academic/managerial	1.91 (1.09–3.35)	1	1.46 (0.76–2.81)	1
Skilled/unskilled/other	2.27 (1.31–3.93)	1.78 (1.14–2.78)	1.33 (0.68–2.61)	1.38 (0.81–2.36)
Income
Low	3.81 (1.86–7.78)	2.14 (1.11–4.14)	2.66 (1.17–6.07)	1.56 (0.73–3.33)
Medium	2.16 (1.08–4.31)	1.49 (0.83–2.48)	1.06 (0.47–2.39)	1.06 (0.54–2.10)
High	0.89 (0.32–2.48)	1	0.76 (0.25–2.34)	1
Health-related characteristics
Fatigue
Often	19.4 (6.56–57.4)	6.47 (3.32–12.7)	10.7 (3.31–34.3)	4.11 (1.97–8.57)
Seldom	1.26 (0.81–1.96)	1	1.05 (0.64–1.70)	1
Anxiety (HADS) (score)
≥ 7	5.53 (3.04–10.1)	4.40 (2.75–7.03)	2.42 (1.18–4.94)	2.76 (1.63–4.67)
< 7	1.74 (1.04–2.92)	1	1.38 (0.79–2.39)	1
Depression (HADS) (score)
≥ 7	18.2 (4.03–82.4)	13.1 (4.30–39.6)	3.64 (0.71–18.6)	4.41 (1.30–15.0)
< 7	1.47 (0.98–2.21)	1	1.18 (0.75–1.87)	1
Support at work
Help and support from colleagues
Seldom/sometimes	3.47 (1.73–6.97)	1.83 (1.03–3.28)	1.33 (0.50–3.50)	0.79 (0.33–1.89)
Often	1.36 (0.88–2.11)	1	1.08 (0.65–1.77)	1
Help and support from supervisor
Seldom/sometimes	3.91 (2.09–7.31)	1.81 (1.06–3.10)	2.40 (1.04–5.54)	1.11 (0.50–2.46)
Often	1.20 (0.76–1.91)	1	0.96 (0.57–1.62)	1
Listened to by colleagues
Seldom/sometimes	2.96 (1.45–6.05)	3.34 (1.79–6.22)	1.76 (0.68–4.54)	1.83 (0.74–4.56)
Often	1.58 (1.03–2.43)	1	1.22 (0.74–2.00)	1
Listened to by supervisor
Seldom/sometimes	1.44 (0.34–6.15)	1.27 (0.50–3.24)	0.53 (0.09–3.20)	0.34 (0.09–1.23)
Often	1.55 (1.05–2.30)	1	1.15 (0.73–1.83)	1
Valued by supervisor
Seldom/sometimes	2.65 (1.28–5.50)	2.59 (1.46–4.61)	0.93 (0.34–2.50)	1.26 (0.58–2.77)
Often	1.62 (1.06–2.49)	1	1.29 (0.79–2.12)	1
Promotion
No/Not possible	2.42 (1.46–4.02)	1.73 (1.10–2.71)	1.77 (0.99–3.17)	1.44 (0.85–2.43)
Yes	1.38 (0.79–2.40)	1	1.11 (0.59–2.10)	1

¹Model 3, adjusted for socioeconomic, health-related and workplace factors.

Bold, significant at the 5% level.

HADS, Hospital Anxiety and Depression Scale.

In the fully adjusted model (Table II), the only socioeconomic factor significantly associated with reduced work ability among breast cancer survivors was low income (OR 2.66; 95% CI 1.17–6.07). In this model, depression was no longer significantly associated with work ability among breast cancer survivors but remained statistically significant among the cancer-free women. Less help and support from a supervisor was significantly associated with reduced work ability (OR 2.40; 95% CI 1.04–5.54) among the cancer survivors.

Discussion

Women who had survived for at least five years after breast cancer and had returned to work reported significantly poorer work ability than cancer-free controls. After adjustment for socioeconomic factors, health-related factors and support at work, the factors most strongly associated with impaired work ability were low income, fatigue and little help and support from a supervisor. Significant associations between these factors and reduced work ability were found for both groups but appeared to be stronger for breast cancer survivors.

The finding that cancer affects work ability has been reported previously in studies of survivors of breast cancer [2,21] and cancers at other sites [22]. In contrast, a Finnish study [12] found that the mean values for current work ability of 591 survivors of early-stage breast cancer, lymphoma, testicular cancer and prostate cancer and 757 cancer-free controls were similar. Testicular cancer survivors had a higher work ability score than their controls; whereas female breast cancer survivors had lower work ability scores than their controls. This difference reflects the complexity of the concept of work ability, in which factors such as age at diagnosis, gender, job type and late effects of cancer treatment all contribute to the score.

In our study, health-related factors were most strongly associated with work ability. After mutual adjustment, we found that fatigue increased the risk of rating low work ability by almost 11 times. Fatigue is a known late effect of cancer treatment and has been shown to be associated with return to work after treatment [23] and to be affected by factors related to the workplace, such as work pressure and work load [24]. In addition, fatigue is closely related to depression, which might explain our observation that the significant association between depression and low work ability disappeared after adjustment for fatigue. Our finding of a close association between fatigue and work ability is not surprising and is also found among cancer-free women but should be kept in mind in the occupational rehabilitation of cancer survivors.

In the model adjusted for age, we found an association between low socioeconomic position and impaired work ability; after adjustment for the other factors, however, only low income was significantly associated. One way of coping with impaired work ability is to reduce the work load, either by changing jobs or by reducing the number of hours, which may imply reduced wages. In that case, low income would be an effect of the association between disease-related factors and low work ability. The measure of income in this study was, however, household income, which may not reflect reduced income of survivors. The fact that income remained significantly associated with low work ability even after adjustment for the other factors indicates that low income is an independent risk factor for the work ability of long-term breast cancer survivors. In general, more affluent people have jobs in which it is possible to adjust work assignments to the late effects of cancer treatment, whereas low income groups might not have the same opportunities to change work tasks, reduce work pressure and work load or control their own work situation.

Inadequate help and support from a supervisor was a significant risk factor for impaired work ability, even after control for health-related factors and socioeconomic position. This finding is in line with those studies in Finland [12,13,25], Norway [26] and France [27], where support from supervisors and a good social climate in the workplace prevented reductions in perceived work ability. These findings indicate that reduced work ability among breast cancer survivors could be prevented by increased help and support from supervisors and co-workers, not only in the months after the end of treatment but also in the long run.

Strengths and limitations

The study was based on a population-based sample of breast cancer survivors identified from a nationwide cancer registry that is considered almost complete, and the questionnaire was composed of validated scales often used for cancer survivors. The study also included an age-matched cancer-free comparison group, making it possible to separate breast cancer-specific effects of the variables.

This study also has some limitations. The overall response rate was 57%, and a further 25% were excluded because of missing values. The response rate was 11% lower among controls than among cases, which might have led to an overestimation of the association between cancer and reduced work ability, because controls with impaired health might have tended not to respond to the questionnaire to the same degree as cases and disease-free controls. There were, however, no significant differences in disease-related factors between the breast cancer survivors who returned the questionnaire and those who did not or who were excluded because of missing values (data not shown). Exclusion of women who were not part of the labour force at time of diagnosis might very well have introduced a ‘healthy worker effect’, resulting in a relatively high work ability score and a selected population that had either found a new balance between personal capacity and work demands or whose cancer was diagnosed at an early stage, resulting in few late effects. The fact that we found an association between impaired work ability and low income, fatigue and lack of social support in this selected population points to an even stronger association closer to the time of diagnosis, when cancer survivors have not left the labour market because of a discrepancy between physical and mental resources and work demands.

Furthermore, we did not have information about work hours or job type. Work ability was measured five to eight years after breast cancer diagnosis. During this period, the women with breast cancer might have adapted to their situation and reduced their working time or type of work, which would result in better self-reported work ability and thus underestimate the association between cancer and work ability.

Conclusion

Although the long-term breast cancer survivors were disease-free and back at work, the working life of some of the survivors was affected to a greater extent than that of the cancer-free women. Breast cancer survivors with low income, who experienced fatigue, and who lacked support from their closest supervisor appeared to be at higher risk for impaired work ability. Care must be taken to help and support these women, not only to return to work but also to adjust their work situation if needed in order to ensure that they can remain on the labour market years after the end of their cancer treatment.

Acknowledgements

We thank the Nordic Cancer Union for supporting the Nordic Study of Cancer and Work. We also thank the National Labour Market Authority, the Danish Municipal VAT foundation and the Graduate School in Public Health Science, University of Copenhagen, for supporting this study. The study was approved by the Danish Data Protection Agency: j.no.2003-41-3331 and j.no 2005-41-4805.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.