A controlled study of job strain in primary-treated cancer patients without metastases

Abstract

To explore job strain in Norwegian primary-treated cancer survivors compared to matched controls from the general population. The study has a cross-sectional, matched case-control design. A sample of 417 employed cancer survivors (208 females with breast cancer and 209 males with testicular or prostate cancer) who had been diagnosed 1–5 years prior to the study and were tumor-free rated themselves on the Demands-Control-Support Questionnaire (DCSQ). Their ratings were compared to those of 417 employed controls from the general population, matched with the survivors on time of investigation, gender, age and municipality of living. No differences in job strain were observed between cancer survivors and controls, or between subgroups of survivors, except that female survivors experienced more strain than males. In certain subgroups statistically significant differences on the DCSQ were found: older survivors showed higher scores on demands than their controls, female survivors reported lower control and higher strain than male survivors, and older male survivors felt higher demands than younger ones. However, the effect sizes of these differences were so small (<0.20) that they hardly were relevant for the work situation. In multivariate analyses survivorship versus control status was not significantly associated with any of the DCSQ measures. The job strain of these cancer survivors did not differ in any work relevant way from their controls, and survivorship status was not significantly associated with job strain. A longer follow-up of survivors is necessary in order to draw conclusion about the stability of these findings over time.

• Cancer
• oncology
• job strain
• demands-control-support questionnaire
• survivors

Among patients diagnosed with cancer in Norway between 1998 and 2002, 15% of the males and 24% of the females were younger than 55 years. Being that the current employment rates in Norway for persons aged 20 to 54 years are 90% for men and 84% for women, a considerable number of cancer patients in this age-range are employed when their malignancy is first diagnosed [1].

The improved prognosis of cancer has increased the amount of research focused on the work situation of cancer survivors, but most of these studies examine return to work and remaining employed after primary treatment, or discrimination at work [2–9]. Occupational stress is another aspect of returning to work after primary cancer treatment. Stress refers to a perception of an imbalance between the demands made and the available resources to match them. In spite of side effects and impairment the cancer patients have to prove to themselves and to coworkers and superiors, who often know about the malignancy, that they are capable workers. Our review of the literature did not show any reports that focus specifically on occupational stress of cancer survivors. A wider search using related terms such as “job strain”, “work-related problems” and “work ability” did not retrieve additional papers either.

During the last 20 years occupational stress and its influence on somatic and mental morbidity has mainly been studied as job strain based on the Job Demand-Control-Support model [10]. Job demands refer primarily to the person's experience of psychological demands such as mental workload, organizational constraints on task completion and conflicting demands [11]. Job control relates to the freedom permitted to the worker to decide how to meet demands and how to perform tasks, and thereby having control over his/hers work activities. Karasek and Theorell [12], [13] defined job strain as a mechanism characterized by lack of balance of demands and control in the work situation, and considered such strain as an important risk factor of work-related morbidity. According to their strain hypothesis, the combination of heavy job demands along with low control over one's own tasks and conduct during the working day, leads to ‘high strain’. In contrast, the combination of low demands and high control results in ‘low strain’ or relaxed jobs.

In the 1980's social support was added to the model and was defined as a person's experience of the interpersonal atmosphere at the workplace regarding support received from co-workers and superiors [14]. The experience of support is scaled from high to low, and Karasek & Theorell accordingly formulated the iso-strain hypothesis, which predicted that the highest morbidity risk for workers was when a worker experienced high strain and low support or isolation (iso-strain jobs). A high level of job strain (strain and iso-strain) has been identified as a risk factor for work-related mental disorders such as anxiety disorders and depression as well as for hypertension [15–22].

With this background the aim of this study was to compare the job strain of tumor-free Norwegian cancer survivors who were actively employed with matched control individuals from the general population using the DCSQ. We also wanted to explore the associations between job strain dimensions on one side and variables concerning demography, mental health, physical quality of life and personality traits on the other. Our first hypothesis was that job strain in cancer survivors would be higher than that observed in matched controls due to the consequences of their disease, and our second hypothesis was that survivorship had a significant association with job strain even when controlled for demography, mental health, physical quality of life and personality traits.

Methods

The Nordic study

This is a Norwegian sub-study of The Collaborative Nordic Study of Cancer and Work Life that examines the living conditions and work situation of cancer survivors in Denmark, Finland, Iceland and Norway. The goal was that each country should collect data from approximately 500 cancer survivors. However, each country was given the opportunity to perform sub-studies of national interest, and it was in this capacity that The Collaborative Nordic Study approved the present study of job strain among Norwegian cancer survivors.

The eligibility criteria of The Collaborative Nordic Study were: 1) A first cancer diagnosis at an age between 25 and 57 years; 2) Primary treatment finished 1 to 5 years prior to the survey (between 1998 and 2002); 3) No evidence of any malignant disease after the primary treatment except basocellular skin cancer; 4) All cancer surgery and chemotherapy should have been terminated, though ongoing adjuvant systemic hormone treatment was allowed for.

Procedure and response rates

Cancer Survivors

In 2004 a questionnaire was mailed to 852 eligible cancer survivors who had been treated at The Cancer Clinic, Rikshospitalet-Radiumhospitalet Medical Center. Among them were 427 females with breast cancer and 425 males with prostate cancer (n = 110) or testicular cancer (n = 315) (Figure 1). Breast cancer is the most common form of cancer in females and affects both younger and older females. Since there was no single type of male cancer with prevalence and age distribution at our clinic that complied with the eligibility criteria of the Nordic project, we covered the age spectrum in males by including those with testicular cancer (younger men) and prostate cancer (older men).

Figure 1.  Subjects and recruitment.

Controls

The Norwegian central institution for public statistic (Statistics Norway) identified the controls from the general population. Each patient was matched with 1 or 2 controls according to availability, based on age, gender and municipality of residence. Altogether 1 548 controls were identified, 777 females and 771 males. [MSOffice1]

The survivors were mailed a questionnaire; and the same questionnaire without cancer-related items was sent to the controls. The survivors got one reminder, but the controls did not receive a reminder in order to protect their anonymity according to a decision made by the Norwegian Data Inspectorate.

Among the survivors, 513 (60%) accepted the invitation to participate, while 219 (26%) did not respond and 120 (14%) refused to participate. Among the controls, 700 (45%) responded by returning a completed questionnaire. Of the 513 responding survivors, 430 (83%) were in full-time or part-time work as were 596 (85%) of the responding controls. Valid job strain forms were returned by 417 (97%) of the working survivors and 570 (96%) of the working controls. In order to get a case-control study, we drew a sample of 417 controls matched by gender and age (10 year groups) to the 417 survivors with valid DCSQ (Figure 1).

Attrition analysis

An attrition analysis of non-compliant (n = 339) and compliant (n = 513) cancer survivors did not show any statistically significant difference as to age, gender, cancer diagnosis, stage and treatment modalities.

Treatment issues

All survivors with breast cancer had local surgery (either mastectomy or lumpectomy with or without axillary lymph node dissection) that was always followed by radiotherapy in cases of breast conserving surgery or detection of axillary lymph node metastases. Dependent on clinical stage, histological grade and/or hormone receptor status of the tumor tissue, adjuvant chemotherapy, hormone treatment and/or regional lymph node irradiation were provided according to standard guidelines.

Survivors with prostate cancer had either retropubic radical prostatectomy or high dose pelvic radiotherapy, which in high-risk patients was combined with adjuvant hormone treatment for 3 years. Survivors with testicular cancer had either entered into a surveillance program, had infra-diaphragmatic radiotherapy or had received chemotherapy followed by resection of residual masses dependent on stage and histology. The extent of testicular cancer was categorized as localized in 81% of the survivors, while 16% had regional and 3% distant metastases.

Measurements

The Demand-Control-Support Questionnaire (DCSQ)

Theorell et al. developed the DCSQ based on the job strain and iso-strain models of Karasek and Theorell [10–14]. The DCSQ has 17 items covering three aspects of job strain that is a subjective, self-reported evaluation of the work situation and is therefore a picture of the work situation seen from the worker's perspective [13–20] (Appendix 1). The demands subscale has five items, the control subscale has six items and the support subscale has six items.

Strain is defined by the demands score divided by the control score, hence higher demands and lower control scores imply more strain. Iso-strain is defined by strain divided by the support score, and thus higher strain and lower support results in higher levels of iso-strain.

Each item of the DCSQ is worded as a statement and is scored on a four-point scale from 1 (right) to 4 (wrong). When adding up the subscale scores all responses are reversed except the responses to the control item # 4 and the demands item # 4. The subscale scores range from 5 (minimum level) to 20 (maximum level) for demands and from 6 to 24 for support and control. Valid scores were calculated if ≥3 of 5 responses were present on the demands subscale, and ≥4 of 6 responses were present on the support and control subscale. In cases where one or two responses were missing, responses were substituted by the mean of the available scores.

The psychometric properties of the DCSQ have been reported as good in its original language as well as in the Norwegian translation [19], and they were re-tested in this study.

Hospital anxiety and depression scale (HADS)

The HADS is a well-established, reliable and validated self-report evaluation instrument designed to detect the presence of anxiety disorders and depression, by two subscales for anxiety (HADS-A) and depression (HADS-D). Caseness of HADS is defined by a cut-off score ≥8 on HADS-A and HADS-D respectively [23]. Due to the high correlation of HADS-A vs HADS-D in our sample (r = 0.63, p < 0.001), only HADS-A was included in the regression analyses.

Short form 12 (SF-12)

Short form 12 (SF 12) is a well-established, reliable and validated self-administrated questionnaire to measure health-related quality of life [24] based on the SF-12 physical (PCS) and mental (MCS) component summary scales. In this paper we only used the PCS subscale, due to the strong correlations between MCS, HADS-A, and HADS-D (MCS-12 vs. HADS-A r = 0.64, MCS-12 vs. HADS-D r = 0.57, both p < 0.001).

The Eysenck Personality Questionnaire (EPQ)

The EPQ-18 is a short version of the original 90 items EPQ covering the personality dimensions of Neuroticism, Extraversion, and Psychoticism with six items each. The correlations between the dimensions of the original EPQ 90-items instrument and the EPQ-18 were .90 and .89 for both EX and NE, and .78 for PS [25–27]. Neuroticism represents the tendency to be emotional and nervous; Extraversion represents the extrovert-introvert dimension. Psychotisism has been theoretically difficult to interpret, and was therefore excluded from the present analyses. Each item on the EPQ-18 is scored as 0 (no) and 1 (yes), and the six item scores on each dimension are added, giving a sum score ranging from 0 to 6 on each dimension.

Other variables

Socio-demographic and work related issues

Variables from the questionnaire were used to measure the socio-demographic characteristics and the socio-economic characteristics of the sample: age at survey, three levels of education (≤9 years, 10–12 years and ≥13 years) and civil status (non-paired, i.e., single/separated/divorced/widowed versus paired, i.e., married/cohabiting). Social class was defined by grouping professions in a way similar to the international Erikson Goldthorpe Portocare social class schema [28], [29] using the Occupation Classification 2000. In this paper Social class I was comprised of higher-grade professionals, administrators and officials who were self-employed higher grade professionals or in a management positions in public or private organizations. Social class II consisted of lower-grade professionals, administrators, officials, higher-grade technicians, and managers in small industrial establishments, supervisors of non-manual employees and armed forces employees. Social class III contained routine non-manual employees of both higher and lower grade; small proprietors such as artisans, farmers and smallholders; others who are self-employed in primary production such as farmers and fishermen; and fishery workers, lower-grade technicians, supervisors of manual workers and skilled, semi-skilled and unskilled manual workers.

Annual household income was defined as the total income of the household. Working time was defined as number of paid work hours per week. Changes in the work career were dichotomized as change of work place/occupation/job tasks or not during the last six years before the survey. If they reported change, the survivors rated whether they thought that the changes were due to their cancer experience or not.

Health-related issues

Self-reported Subjective health status was rated on a Likert scale with five response alternatives ranging from good (1) to very bad (5), and was then recoded into three categories (very good/good, moderate, and bad/very bad). The symptoms of tiredness, nervousness, concentration problems, headache, palpitation, vertigo, nausea, chest pain, stomach ache and insomnia were scored on Likert scales with five response alternatives from 0 (never) to 4 (all the time). The Overall symptom score was the sum of these 10 items scores [range from 0 (no symptoms) to 40 (maximum symptoms)].

Based on diagnosis or treatment by physicians, the following co-morbidities were self-reported: injuries, musculoskeletal disease, cardiovascular disease, respiratory disease, mental disorder or several mental health problems, metabolic disease, neurological or sensory disease or other severe diseases. The total number of conditions reported was dichotomized into none or ≥1 (Co-morbidity).

Statistics

The completed questionnaires were scanned into a database, and the data were converted into a SPSS file for statistic analyses. The calculations were performed on SPSS for PC version 12.0. Dimensional variables were analyzed by t-tests, and in case of skewed distributions, non-parametric tests were applied. Differences between groups were also calculated as effect sizes, and clinical/work relevant sizes were >0.20 [30]. Categorical variables were analyzed by χ² tests, and clinical/work relevant differences between groups were > 10% [30]. The psychometric features of the DCSQ were examined for internal consistency with Cronbach's coefficient alpha and by principal component analysis with varimax rotation.

The associations of relevant variables and the DCSQ subscale scores, as well as the strain and iso-strain scores, were examined with hierarchical multivariate linear regression analyses. The strength of associations was expressed by standardized (β) beta coefficients, R²-change and R-change. The statistical significance level was set at p < 0.05, and all tests were two-tailed.

Ethics

The study was approved by the Regional Committee for Medical Research Ethics of South Norway and approved by the Norwegian Data Inspectorate. Survivors and controls received written information about the study, but only the survivors had to return written informed consent.

Results

Socio-demographic, work and health-related findings

Female survivors had higher mean age than their controls (p = 0.01) (Table I). A lower proportion of female survivors belonged to social class I, and a higher proportion to class II compared to controls (p < 0.001). Compared with their controls a lower proportion of male survivors were in paired relationships (p = 0.04), and they worked more hours per week (p = 0.003). The mean Overall symptom score was also higher in male survivors compared to controls (p = 0.02). The PCS mean score and the level of depression were significantly lower in female survivors compared to controls. The level of anxiety was significantly higher in male survivors compared to controls. Both female and male survivors showed significantly higher mean score on neuroticism and extraversion compared to their controls.

Table I.  Socio-demographic, work and health-related characteristics of the samples of survivors and controls according to gender.

	Females			Males
	Survivors (n = 208)	Controls (n = 208)	p	Survivors (n = 209)	Controls (n = 209)	p
Age, mean (SD)	52.8 (6.6)	51.3 (5.9)	0.01	44.8 (10.2)	45.4 (9.5)	0.52
Education, N (%)			0.22			0.08
≤ 9 years	17 (8)	28 (14)		20 (10)	16 (8)
10–12 years	97 (47)	94 (45)		92 (44)	92 (45)
≥ 13 years	93 (45)	86 (41)		96 (46)	99 (47)
Civil status, N (%)			0.17			0.04
Non-paired	49 (24)	37 (18)		48 (23)	32 (15)
Paired	155 (76)	164 (82)		157 (77)	175 (85)
Social class, N (%)			<0.001			0.43
Class I	70 (36)	85 (44)		87 (43)	83 (41)
Class II	110 (57)	76 (39)		69 (34)	81 (40)
Class III	13 (7)	33 (17)		45 (23)	38 (19)
Annual household income, mean (SD)	10.1 (2.4)	10.3 (2.3)	0.52	10.5 (1.9)	10.7 (1.9)	0.31
No of paid work hours/week, mean (SD)	27.0 (14.9)	29.5 (19.2)	0.16	35.6 (10.2)	32.0 (13.7)	0.003
Changed work place	49 (24)	60 (29)	0.24	66 (32)	75 (36)	0.37
Due to cancer	18 (9)	*NA		11 (5)	*NA	0.17
Changed occupation	27 (13)	34 (17)		39 (19)	28 (14)	0.13
Due to cancer	11 (5)	*NA	0.29	9 (4)	*NA	0.64
Changed job tasks	72 (35)	90 (43)	0.08	94 (45)	101 (48)	0.55
Due to cancer	27 (13)	*NA		18 (9)	*NA	0.15
Subjective health status, N (%)			0.33			0.06
Very good/good	148 (71)	157 (76)		146 (70)	167 (80)
Moderate	0 (0)	1 (1)		2 (1)	1 (1)
Very bad/bad	59 (29)	49 (23)		61 (29)	41 (19)
Overall symptom score, mean (SD)	10.9 (5.8)	10.3 (5.3)	0.29	9.2 (5.9)	8.0 (4.5)	0.02
Co-morbid diseases N (%)			0.78			0.24
No	107 (52)	106 (54)		134 (65)	117 (59)
Yes	98 (48)	92 (46)		73 (35)	81 (41)
Currently on sick leave	14 (7)	14 (7)	1.00	9 (4)	12 (6)	0.50
HADS Depression score, mean (SD)**	2.6 (3.0)	2.9 (3.0)	0.01	2.4 (2.7)	2.6 (2.7)	0.16
HADS Anxiety score, mean (SD)**	5.0 (3.7)	4.9 (3.9)	0.75	4.7 (3.6)	3.7 (2.8)	0.003
SF-12 PCS, mean (SD)	47.1 (9.6)	49.8 (8.8)	0.01	50.8 (8.5)	51.4 (7.6)	0.52
EPQ-18, mean (SD)**
Neuroticism	2.8 (1.9)	2.4 (1.9)	0.002	2.2 (1.9)	1.9 (1.7)	0.04
Extraversion	4.1 (1.6)	3.7 (1.8)	0.02	4.1 (1.7)	3.9 (1.7)	0.02

*NA = Not applicable. ** p-values based on non-parametric test. p-values for comparisons of male and female survivors only.

Psychometrics of the DCSQ

The analyses were done separately for the survivors (n = 417) and the control sample (n = 417). Principal component analysis showed a three factor rotated solution in accordance with the three subscales of DCSQ in both samples, and that solution explained 50.9% of the variance in survivors and 50.6% in controls. Internal consistency measured by Cronbach's alpha was: for support 0.79 in survivors vs. 0.83 in controls; for control 0.74 vs. 0.70; and for demands 0.78 vs. 0.73.

DCSQ findings

The mean values of the DCSQ subscales are shown in Table II. Except for more strain in female survivors compared to male survivors (p = 0.04), no significant differences were observed for strain or iso-strain between survivors and controls or between survivors. Survivors ≥50 years had higher mean levels of demands than their controls (p = 0.01). Male survivors reported higher mean levels of control (p ≤ 0.001). Male survivors ≥50 years experienced more demands than those <50 years (p = 0.04).[MSOffice3]

Table II.  Mean values of DCSQ subscales score according to gender, age and diagnosis.

	Females			Males
	Survivors n = 208 Mean (SD)	Controls n = 208 Mean (SD)	p	Survivors n = 209 Mean (SD)	Controls n = 209 Mean (SD)	p
Demands	13.2 (3.0)	12.8 (2.6)	0.19	13.2 (2.7)	13.1 (2.6)	0.71
Control	17.2 (3.2)	17.1 (2.7)	0.91	18.2 (2.9)	17.9 (3.1)	0.36
Support	19.4 (2.6)	19.9 (2.6)	0.34	19.6 (2.6)	19.9 (2.0)	0.31
Strain	0.8 (0.22)	0.8 (0.23)	0.32	0.8 (0.22)	0.8 (0.23)	0.65
Iso-strain	0.04 (0.02)	0.04 (0.02)	0.11	0.04 (0.01)	0.04 (0.02)	0.67
	Respondents < 50 year			Respondents ≥ 50 year
	Survivors n = 194 Mean (SD)	Controls n = 180 Mean (SD)	p	Survivors n = 223 Mean (SD)	Controls n = 237 Mean (SD)	p
Demands	12.9 (2.9)	13.2 (2.6)	0.33	13.4 (2.8)	12.8 (2.7)	0.01
Control	17.9 (3.1)	17.7 (3.1)	0.53	17.5 (3.0)	17.4 (2.8)	0.75
Support	19.5 (2.7)	19.9 (2.8)	0.25	19.4 (2.6)	19.4 (2.8)	0.06
Strain	0.7 (0.2)	0.8 (0.2)	0.17	0.8 (0.2)	0.8 (0.2)	0.07
Iso-strain	0.04 (0.01)	0.04 (0.02)	0.39	0.04 (0.02)	0.04 (0.02)	0.06
	Cancer survivors
	Females n = 208 Mean (SD)			Males n = 209 Mean (SD)		p
Demands	13.2 (3.0)			13.2 (2.7)		1
Control	17.2 (3.1)			18.2 (2.9)		<0.001
Support	19.4 (2.6)			19.6 (2.6)		0.36
Strain	0.8 (0.2)			0.7 (0.2)		0.04
Iso-strain	0.04 (0.02)			0.04 (0.01)		0.05
	Male cancer survivors
	Testicular cancer n = 163 Mean (SD)			Prostate cancer n = 46 Mean (SD)		p
Demands	13.1 (2.8)			13.4 (2.5)		0.6
Control	18.2 (2.9)			18.1 (2.8)		0.76
Support	19.7 (2.5)			19.2 (2.8)		0.3
Strain	0.7 (0.2)			0.8 (0.2)		0.52
Iso-strain	0.04 (0.01)			0.04 (0.02)		0.33
	Females survivors			Males survivors
	<50 years n = 112 Mean (SD)	≥50 years n = 304 Mean (SD)	p	<50 years n = 262 Mean (SD)	≥50 years n = 156 Mean (SD)	p
Demands	12.6 (3.3)	13.4 (2.9)	0.09	13.1 (2.7)	13.4 (2.7)	0.04
Control	17.4 (3.2)	17.1 (3.1)	0.5	18.2 (3.0)	18.3 (2.7)	0.74
Support	19.3 (2.7)	19.4 (2.6)	0.83	19.6 (2.6)	19.5 (2.6)	0.67
Strain	0.7 (2.2)	0.8 (0.2)	0.05	0.7 (0.2)	0.8 (0.2)	0.71
Iso-strain	0.04 (0.02)	0.04 (0.02)	0.16	0.03 (0.01)	0.04 (0.02)	0.71

Associations with the DCSQ subscales, strain and iso-strain

As to the DCSQ subscales, being a cancer survivor was not significantly associated with any of them, and in contrast increasing level of anxiety was significantly associated with all of them (Table III). Among demographic variables, increasing household income was associated with increasing levels of demands, while being female was associated with lower levels of control. The block of somatic variables contributed significantly to the variance of the demands and support scores. Higher score on the personality trait of neuroticism was significantly associated with higher support score, while higher extraversion was associated with higher control score.[MSOffice4]

Table III.  Hierarchical multiple linear regression analysis with DCSQ demands, control and support as the dependent variable.

Independent variables	Beta	p	R^2	R^2-change	p
DCSQ Demands
Step 1. Survivor versus control	0.02	0.70	0.001	0.001	0.40
Step 2. Demography
Age	−0.07	0.12
Gender	0.000	0.99
Civil status	−0.004	0.93
Level of education	−0.07	0.09
Social class	−0.03	0.38
Paid working hours	0.06	0.14
Step 3. Somatic variables	0.14	0.01	0.03	0.03	0.02
Household income
Number of somatic symptoms	0.03	0.59
Number of comorbid diseases	0.02	0.67
Physical Quality of life (PCS-12)	−0.03	0.51	0.05	0.02	0.001
Step 4. Anxiety	0.10	0.06	0.07	0.02	0.001
Step 5. Personality traits
Neuroticism	0.09	0.08
Extraversion	−0.05	0.26	0.07	0.01	0.07
Step 1. Survivor versus control	0.01	0.70	0.001	0.001	0.50
Step 2. Demography
Age	0.01	0.88
Gender	−0.12	0.002
Civil status	−0.007	0.86
Level of education	−0.31	<0.001
Social class	0.01	0.86
Paid working hours	0.01	0.75
Household income	0.05	0.26	0.14	0.14	<0.001
Step 3. Somatic variables
Number of somatic symptoms	0.06	0.19
Number of comorbid diseases	0.01	0.83
Physical Quality of life (PCS-12)	−0.06	0.15	0.14	0.01	0.17
Step 4. Anxiety	−0.09	0.08	0.16	0.13	0.001
Step 5. Personality traits
Neuroticism	−0.09	0.05
Extraversion	0.20	<0.001	0.20	0.05	<0.001
Step 1. Survivor versus control	−0.01	0.71	0.002	0.002	0.20
Step 2. Demography
Age	0.13	0.75
Gender	0.05	0.26
Civil status	0.07	0.11
Level of education	0.05	0.24
Social class	0.04	0.24
Paid working hours	0.02	0.67
Household income		0.10	0.01	0.004	0.89
Step 3. Somatic variables
Number of somatic symptoms	−0.18	<0.001
Number of comorbid diseases	−0.03	0.45
Physical Quality of life (PCS-12)	−0.03	0.53	0.11	0.10	<0.001
Step 4. Anxiety	−0.09	0.10	0.13	0.02	<0.001
Step 5. Personality traits
Neuroticism	0.14	<0.001
Extraversion	−0.17	<0.001	0.17	0.43	<0.001

Being a cancer survivor was not associated with strain or iso-strain (Table IV). Somatic variables, level of anxiety and personality traits were all significantly associated with both strain and iso-strain. Increasing level of anxiety and more somatic symptoms were significantly associated with increasing levels of strain and iso-strain. More neuroticism was associated with lower level of strain and higher level of iso-strain, while the opposite pattern was observed for the extaversion trait.[MSOffice5]

Table IV.  Hierarchical multiple linear regression analysis with strain and isostrain as dependent variables.

Independent variables	Beta	p	R^2	R^2-change	p
Strain
Step 1. Survivor versus control	−0.001	0.10	0.000	0.000	0.86
Step 2. Demography
Age	−0.05	0.27
Gender	0.05	0.20
Civil status	0.01	0.86
Level of education	0.15	<0.001
Social class	−0.04	0.33
Paid working hours	0.02	0.57
Household income	0.57	0.24	0.03	0.03	0.002
Step 3. Somatic variables
Number of somatic symptoms	−0.05	0.38
Number of comorbid diseases	0.01	0.80
Physical Quality of life (PCS-12)	0.002	0.97	0.05	0.02	0.02
Step 4. Anxiety	0.13	0.02	0.08	0.03	<0.001
Step 5. Personality traits
Neuroticism	−0.15	<0.001
Extraversion	0.15	0.03	0.12	0.04	<0.001
Independent variables	Beta	p	R^2	R^2-change	p
Iso-Strain
Step 1. Survivor versus control	−0.01	0.78	0.000	0.000	0.80
Step 2. Demography
Age	−0.04	0.39
Gender	0.002	0.96
Civil status	−0.01	0.76
Level of education	0.09	0.02
Social class	−0.04	0.32
Paid working hours	−0.002	0.95
Household income	0.05	0.29	0.02	0.02	0.11
Step 3. Somatic variables
Number of somatic symptoms	0.03	0.55
Number of comorbid diseases	0.01	0.41
Physical Quality of life (PCS-12)	0.02	0.74	0.07	0.05	<0.001
Step 4. Anxiety	0.14	0.01	0.10	0.04	<0.001
Step 5. Personality traits
Neuroticism	0.18	<0.001
Extraversion	−0.16	<0.001	0.16	0.05	<0.001

Discussion

The main finding of this study was contrary to our first hypothesis as no statistically significant differences were observed regarding job strain or iso-strain between the cancer survivors and their controls. Among cancer survivors, females experienced significantly more strain than males. Male survivor's ≥50 years experienced significantly more job demands than young male survivors. Contrary to our second hypothesis, being a cancer survivor was not significantly associated with strain, iso-strain or any of the DCSQ subscales scores. Somatic variables, anxiety and personal traits were significantly associated with both Strain and Iso-strain while Demographical variables only were significantly associated with Strain.

Although statistically significant, numerically the differences on strain, iso-strain and the DCSQ subscales were small, and so were the effect sizes. These differences therefore hardly have any work-related relevance.

The associations of the DCSQ subscales with personality dimensions are in accordance with the findings of Parkes et al. [20], and with anxiety in accordance with Sanne et al. [19].

Studies analyzing job strain have examined patients with hypertension, and showed that high scores on strain and iso-strain are associated with increased risk of cardiovascular events [21]. The prospective cohort from the British Whitehall II study showed increased risk of coronary heart disease in groups with high job strain [22], and the Norwegian Hordaland health study from Norway showed that high demands, low control and low support, individually and especially when combined, were risk factors for anxiety and depression [19].

Strength and weaknesses

Our study is the first study that measures job strain in cancer survivors and matched controls using a well-established instrument for job-strain with good psychometric properties in its Norwegian version [17], [19]. These properties were confirmed in our study.

All female survivors had the diagnosis of local or regional breast cancer, and had been treated by similar standard therapies, and they represent a homogenous cohort of both younger and older female survivors. The male survivors consisted of two cancer types in order to comply with the criteria for age and sample size of the Nordic study. Although the work situation could be significantly different for younger and older survivors, the job strain scores did not suggest this as there was no significant difference between the scores of these two subgroups. An unfortunate limitation of our study was the lack of registrations of the de facto practical working conditions in our samples. With such data, other interesting subgroup analyses could have been run.

A response rate of approximately 60% for a questionnaire study of cancer survivors is not optimal. Patients treated at our hospital are exposed to several follow-up investigations particularly those with breast- and testicular cancer, and this fact can explain the low response rate among these cancer survivors. The attrition analysis showed no significant differences between responding and non-responding cancer survivors in the variables available for examination. We therefore suggest that our findings can be generalized to the sample of cancer survivors who do not relapse, are below 57 years of age at primary treatment and join the labor force after successful curative treatment. However, we cannot reject the possibility of selection bias since there is a possibility that those with the most successful work situation are the ones who responded positively to our invitation. The same bias could also be operating in the controls.

Given that questionnaires sent to the general Norwegian population without incentives or reminders have a response rate in the range of 45–60%, the 45% response rate of the controls without reminders in our study is acceptable. It is also important to consider that the controls were matched to the survivors on age, sex and place of dwelling, so the low response rate was less important.

It is a limitation of our study that we only have examined survivors of early stage breast, prostate and testicular cancer. Examination of other types and more advanced stages of cancer could lead to quite different findings concerning job strain.

Conclusion

In this matched case-control study of self-rated job strain in employed tumor-free cancer survivors within 5 years after primary treatment, job strain was similar to that of age and gender-matched controls from the general population. In multivariable analyses, survivor status was not associated with job strain, but strain was associated with demographic and somatic variables, anxiety and personality traits.

These encouraging findings are tempered when we consider the relatively short follow-up time as the job strain of cancer survivors may worsen over time resulting in co-morbidity, early retirement or more frequent and extended periods of sick leave.

Acknowledgements

The Norwegian Foundation for Health and Rehabilitation and the Nordic Cancer Union sponsored this study (Grant no H0-5010/002).

Appendix 1

The Demand–Control–Support Questionnaire (DCSQ)^a

Table

Subscale name and item number	Item text
Demands (D)
D1	Does your job require you to work very fast?
D2	Does your job require you to work very hard?
D3	Does your job require too great a work effort?
D4	Do you have sufficient time for all your work tasks?
D5	Do conflicting demands often occur in your work?
Control (C)
C1/SD1	Do you have the opportunity to learn new things in your work?
C2/SD2	Does your work require skills?
C3/SD3	Does your job require creativity?
C4/SD4	Does your job require doing the same tasks over and over again?
C5/DA1	Do you have the possibility to decide for yourself how to carry out your work?
C6/DA2	Do you have the possibility to decide for yourself what should be done in your work?
Social support (S)
S1	There is a quiet and pleasant atmosphere at my place of work
S2	There is good collegiality at work
S3	My co-workers (colleagues) are there for me (support me)
S4	People at work understand that I may have a ‘‘bad’’ day
S5	I get along well with my supervisors
S6	I get along well with my co-workers

^aThe translation into English from the Norwegian version was done by the authors, and is not authorized. From page 167 in: “Swedish Demand–Control Support Questionnaire: Factor structure, item analyses, and internal consistency in a large population.” Scandinavian Journal of Public Health, 2005; 33:166–174.