Int Arch Occup Environ Health DOI 10.1007/s00420-013-0882-9

ORIGINAL ARTICLE

Chronic health conditions and work ability in the ageing workforce: the impact of work conditions, psychosocial factors and perceived health Wendy Koolhaas • Jac J. L. van der Klink Michiel R. de Boer • Johan W. Groothoff • Sandra Brouwer

•

Received: 14 April 2012 / Accepted: 3 May 2013 Ó Springer-Verlag Berlin Heidelberg 2013

Abstract Purpose The aim of this study was to determine the influence of work conditions, psychosocial factors and perceived health on the association between the presence of a chronic health condition and (single-item) work ability among workers aged 45 years and older. In addition, we aimed to examine variables associated with work ability for workers with and without a chronic health condition separately. Methods The data of this cross-sectional study were obtained from 5,247 workers aged 45 years and older in five different work sectors. Work ability was assessed with the first item of the Work Ability Index. The presence of a chronic health condition was assessed by self-report. Independent variables in the multivariable linear regression analysis were work conditions, psychosocial factors and perceived health status. Results The presence of a chronic health condition was negatively associated with work ability (B = -0.848). The strength of this association slightly attenuated after subsequently adding individual characteristics (B = -0.824), work conditions (B = -0.805) and more so after adding psychosocial factors (B = -0.704) and especially perceived health variables (B = -0.049) to the model.

W. Koolhaas (&)
J. J. L. van der Klink
M. R. de Boer
J. W. Groothoff
S. Brouwer Department of Health Sciences, Community and Occupational Medicine, University Medical Center Groningen, University of Groningen, Antonius Deusinglaan 1, FA10, Room 621, 9713 AV, Groningen, The Netherlands e-mail: [email protected] M. R. de Boer Department of Health Sciences, VU University, Amsterdam, The Netherlands

Variables associated with work ability for workers with and without a chronic health condition were similar. Conclusion Perceived health and psychosocial factors, rather than work conditions, explained the association between the presence of a chronic health condition and work ability. Substantial differences in variables associated with work ability for workers with and without a chronic health condition were not found. Based on the lower mean scores for workers with a chronic health condition and work ability as well for predictors, these workers might have the most benefit by a policy focussing on enhancing these associated variables. Keywords Ageing workers
Chronic health condition
Perceived health
Psychosocial factors
Work ability
Work conditions

Introduction There is ample evidence for the burden of chronic conditions on health and work outcomes (Alavinia and Burdorf 2008; Karpansalo et al. 2004; Plat et al. 2011; Schuring et al. 2007). Given the fact that the prevalence of chronic conditions increases with age and that person will be required to work until higher ages, the prevalence of chronic conditions in the working population can be expected to increase even further (Ilmarinen 2005; Ilmarinen et al. 2005). This might hamper the contribution of large parts of the working-age population to the work process, especially for workers aged 45 years and older. A recent study showed that in the Dutch working population of 45 years of older, one in three workers indicated a chronic health condition (Koolhaas et al. 2012). Chronic health conditions have an adverse impact on the

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employability of workers (Baanders et al. 2002; Lerner et al. 2003; Schultz et al. 2009). Previous research on differences between workers with and without a chronic health condition shows that workers with a chronic health condition experience more problems due to ageing, more barriers to perform work, more support needs and lower work ability scores (Koolhaas et al. 2012). For sustainable employability, it is crucial that work demands are adjusted to the health status and abilities of the individual worker. Within this framework, the concept of work ability has been developed as an important multifactorial concept that can be used to identify workers at risk for an imbalance between health, personal resources and work demands (Ilmarinen 2001; Tuomi et al. 1998). The work ability concept is based on the assumption that work ability is determined by an individual’s perception of the demands at work and the ability to cope with them. Previous research showed that work ability, measured with the Work Ability Index (WAI), is negatively influenced by older age, high physical work demands, high psychosocial work demands, unhealthy lifestyle and a poor physical fitness (Alavinia et al. 2007; Ilmarinen et al. 1997; Pohjonen 2001; Tuomi et al. 2001; van den Berg et al. 2008). It is also known from the literature that it is crucial to promote social support and networks at the workplace and in private life, as well as a coping-oriented approach to health issues and social life in order to strengthen work ability among female employees in elderly care (Sandmark et al. 2009). Furthermore, lower work ability levels have been shown to result in decreased work performance, productivity loss, long-term sickness absence and early exit from work (Ahlstrom et al. 2010; Ilmarinen et al. 1997; Koolhaas et al. 2012; Robroek et al. 2009; Salonen et al. 2003; Schultz et al. 2009; Sell et al. 2009). In addition, several studies have established a strong association between perceived health status and work ability (Ahlstrom et al. 2010; Gamperiene et al. 2008; Koskinen et al. 2008; Sorensen et al. 2008; Tuomi et al. 1991). Although previous studies confirmed the associations between psychosocial, work-related factors and perceived health on work ability in different occupational populations and age groups, to our knowledge, none of these studies so far have studied the impact of these potential explanatory factors on the association between the presence of a chronic health condition and work ability. One of the underlying reasons might be that the WAI is an instrument that contains many disparate questions more or less indirectly measuring work ability (e.g. relating to diagnosis of chronic conditions and sick leave). This may have implications when the WAI is used among workers already on sick leave; also, it may give too much weight to diagnoses not necessarily related to work ability (Ahlstrom et al.

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2010). As a result, the single-item question on work ability has often replaced the WAI in clinical and occupational practice (Ahlstrom et al. 2010; de Croon et al. 2005; Sluiter and Frings-Dresen 2008). Ahlstrom found strong associations between the WAI and the single-item question with sick leave, health and symptoms among long-term sicklisted women working in human service organizations. Moreover, they found strong predictive value for the degree of sick leave and health-related quality of life for the single-item question. Although further validation studies are still lacking, the single-item question on work ability may be a good alternative to the WAI. The benefits of using the single-item question in our study is that it could be used as an indicator for assessing the status of work ability among workers with and without a chronic health condition without given too much weight to diagnoses not necessarily related to work ability when using the WAI. The main purpose of this study is to determine the impact of work conditions, psychosocial factors and perceived health on the association between the presence of a chronic health condition and work ability among workers aged 45 years and older. In addition, variables associated with work ability level will be examined for workers with and without a chronic health condition separately.

Methods Design and study population The data of this cross-sectional survey study were obtained from workers aged 45 years and older who worked in ten different organizations in the Netherlands. These organizations represent five different sectors: production industry, education, health care, government and telecommunication. A self-administered questionnaire was sent to all participants (n = 13,897). All companies enclosed a letter of recommendation. The anonymity of respondents and confidentiality of the information they provided were guaranteed. Four weeks after the initial mailing, all workers received a written reminder. Information from questionnaires was available from 5,730 workers. The overall response was 40 % varying from 28 % (health care) to 58 % (production) across organizations. Because of incomplete data, 483 workers (8 %) were excluded from the analyses. These workers with missing values had significantly lower mean scores on years of paid work (-1.35 years) and active coping (-0.60 points) and consisted of a significantly higher percentage of women (42 vs 33 %), lower educated workers (29 vs 22 %), executive workers (56 vs 46 %), production workers (18 vs 4 %),

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workers with physical work (15 vs 6 %) and lower percentages of workers with mental work (55 vs 65 %) or working in the sector telecommunication (31 vs 49 %) than those workers included in the study. Ethical approval was sought from the Medical Ethics Committee of the University Medical Center Groningen, which advised that, according to Dutch law, ethical clearance was not required for this cross-sectional study.

Psychosocial factors

Data of age, gender and education were collected by questionnaire. Age was based on the calendar age of the workers. The highest education level successfully completed was categorized into low (no education, primary or secondary education) and high (post-secondary education).

Perceived work attitude was measured with the Dutch language version of the Work Involvement Scale (WISDLV), reflecting the degree to which a person wants to be engaged in work (Warr et al. 1979). The questionnaire consists of six items with responses on a 1–4-point scale (strongly disagree, disagree, agree and strongly agree). Higher scores on the WIS-DVL indicate a more positive attitude towards work. The internal consistency (Cronbach’s alpha) of the WIS-DLV in this study was 0.72. The Utrecht Coping List (UCL) was used to assess styles of coping (Schreurs et al. 1993). This questionnaire was designed to measure the coping strategies people use in stressful situations. In this study we used the short version of the original 47-item Utrecht Coping List (UCL; Schreurs et al. 1993) which includes a selected number of dimensions and items and consists of three scales: (1) active problem-focusing (five items), (2) expression of emotions (four items) and (3) avoidance behaviour (four items). We used the active and passive coping styles in this study which were shown to be important constructs in other work- and health-related studies (Carver and Connor-Smith 2010; Shimazu and Schaufeli 2007; van Rhenen et al. 2008). The internal consistencies as well as the test–retest reliabilities have been shown to be satisfactory (Schreurs et al. 1993). The internal consistencies found for active problem-focusing, expression of emotions and avoiding focused coping strategies in this study were 0.84, 0.70 and 0.71, respectively. Perceived support was measured with a self-constructed scale reflecting a person’s perception of social support. The 14 items were answered on a 5-point Likert scale (totally disagree to totally agree). A confirmatory factor analysis was carried out in three subscales: (1) co-workers’ support (two items), (2) community support (six items) and (3) organizational support (six items). Higher scores indicate more support for all scales. The internal consistencies for co-workers, community and organizational support in this study were 0.66, 0.70 and 0.72, respectively.

Work conditions

Health status

Organizations were categorized in the following sectors: production, education, health care, government and telecommunication. Participants were asked in which of the following occupational areas they worked: executive, secretarial, policy or management. The duration of the current function and years of paid work were reported in years. A dichotomous (yes/no) question was used to assess shift work. Self-reported work type assessed with a single question, based on the question in the WAI, was used to classify workers into mental, physical or both.

Perceived health status was assessed with the Dutch version of the SF-36 Health Survey consisting of eight multiitem scales: physical functioning, role limitations due to physical health problems, pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems and mental health (Van der Zee and Sanderman 1993). Higher scores indicate higher levels of functioning and health (range 0–100). The internal consistency of the subscales was between 0.74 (subscale general health) and 0.89 (subscale role limitations for

Work ability Self-reported work ability was measured by the first item of the work ability index: ‘current work ability compared with the lifetime best’. The value 0 represents ‘completely unable to work’ and 10 the ‘work ability at its best’ (Tuomi et al. 1998). Previous research has established that the single-item question on work ability can be used as a reliable indicator for assessing the status and progress of work ability (Ahlstrom et al. 2010; Sell et al. 2009; Sluiter and Frings-Dresen 2008; van den Berg et al. 2008). Chronic health condition We defined a chronic disease as ‘the subjective experience of a long-term irreversible disease of more than 3-month duration’, which is in accordance with many other studies (Beatty and Joffe 2006; Klerk 2000; Koolhaas et al. 2012). It was assessed by asking the respondents the following question: ‘Do you currently have a long-term or chronic disease of more than 3-month duration without the prospect of recovery?’ (yes/no). Individual characteristics

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Int Arch Occup Environ Health Table 1 Baseline characteristics of the study population with subgroup analyses for workers with and without a chronic health condition Characteristics

Total population (n = 5,247) N

Age (year) Gender Male Female Education Low High Chronic health condition (yes) Work conditions Occupation Executive Secretarial Policy Management Sector Production Education Health care Government Telecommunication Current function (years) Paid work (years) Work type Mental Physical Both mental and physical Shift work (yes) Psychosocial factors Work attitude Coping Active problem-focusing Expression of emotions Avoidance behaviour Support Co-workers Community Organizational Perceived health status Physical functioning Social functioning Role limitations from physical problems Role limitations from emotional problems Mental health Vitality Pain General health Work ability Work ability score single-item

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Mean (SD)

(%)

Without a chronic health condition (n = 3,395)

With a chronic health condition (n = 1,852)

N

N

53.0 (4.4)

Mean (SD)

(%)

Mean (SD)

52.9 (4.5)

(%)

53.3 (4.3)

3,508 1,739

67 33

2,348 1,047

69 31

1,160 692

63 37

1,181 4,066 1,852

23 77 35

692 2,703

20 80

489 1,363 1,852

26 74 100

2,429 1,063 1,009 746

46 20 20 14

1,512 658 695 530

45 19 20 16

917 405 314 216

50 22 17 11

192 1,170 1,099 212 2,574

4 23 20 4 49

118 743 676 143 1,715

3 22 20 4 51

74 427 423 69 859

4 23 23 4 46

21.6 (11.6) 31.9 (7.0) 3,446 311 1,490 586

21.3 (11.6) 31.6 (6.9) 66 6 28 11

2,322 180 893 368

22.1 (11.6) 32.4 (7.0) 68 6 26 11

1,124 131 547 218

61 7 32 12

66.1 (19.8)

67.5 (19.1)

63.4 (20.9)

14.8 (2.6) 8.4 (1.9) 8.2 (2.0)

14.8 (2.6) 8.4 (1.8) 8.1 (2.0)

14.7 (2.6) 8.6 (2.0) 8.3 (2.0)

4.2 (2.0) 24.0 (4.7) 19.5 (4.0)

4.1 (2.0) 24.4 (4.5) 19.6 (3.9)

4.4 (2.0) 23.4 (4.8) 19.4 (4.3)

90.2 84.8 77.2 81.5 70.1 63.3 84.5 69.8

94.3 89.8 86.2 86.4 72.1 66.6 91.1 75.2

82.7 75.7 60.7 72.6 66.4 57.2 72.5 59.9

(14.2) (19.8) (36.3) (35.2) (12.3) (14.2) (19.2) (17.3)

8.1 (1.4)

(9.6) (15.5) (28.9) (30.7) (10.7) (12.6) (14.4) (14.0)

8.4 (1.2)

(17.7) (23.2) (42.1) (40.7) (13.9) (15.0) (21.0) (18.4)

7.5 (1.6)

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physical problems and role limitations for emotional problems). Statistical analyses Multivariable linear regression analysis was performed to examine the impact of the potential explanatory factors (i.e. work conditions, psychosocial factors and perceived health status) on the association between the presence of a chronic health condition and work ability. To estimate to what extent this association could be explained by the predictors, multiple linear regressions were performed using a forward stepwise method. In this method, predictors were entered (forwards) in blocks. In model 1 chronic health condition was entered. The individual characteristics were entered in model 2, followed by the work conditions in model 3, the psychosocial factors in model 4 and the perceived health status variables in model 5. To determine the impact of the work conditions, psychosocial factors and perceived health on the association between the presence of a chronic health condition and work ability, we included all variables which were significantly associated in the stepwise analyses of model 1–5 in all models. Subsequently, we separately added the potential variables to the multivariate model which were not statistically significant in the univariate analysis to determine their association with the outcome measure in the presence of other prognostic factors. To determine variables associated with work ability for workers with and without a chronic health condition, analyses were stratified by the presence of a chronic health condition. All significant variables in the multivariable model for one of the groups were included in the models for other groups as well in order to provide an appropriate comparison. The level of significance for all statistical tests was set at an alpha of 0.05 (2-sided) using the Statistical Package for the Social Sciences (SPSS, Inc, Chicago, IL, USA), version 16.0.

Results The study population included 3,508 men (67 %) and 1,734 women (33 %) of the five different sectors: production (4 %), education (23 %), health care (20 %), government (4 %) and telecommunication (49 %). The mean age of the workers was 53.0 years (SD 4.4) ranging from 45 to 64 years of age. The majority (77 %) of the workers were highly educated. The mean score on work ability was 8.1 (SD 1.4, median 8.0) ranging from 0 to 10. Detailed information about these characteristics is presented in Table 1. Thirty-five per cent (n = 3,395) of the workers had a chronic health condition, with the highest prevalence for musculoskeletal conditions (n = 1,497, 81 %),

neurological or sensory disease (n = 654, 35 %) and cardiovascular diseases (n = 634, 34 %) (data not shown). Table 2 shows that the presence of a chronic health condition was negatively associated with work ability (B = -0.848). The effect of the individual characteristics and work conditions on this association was small (B = -0.805), but the regression coefficient attenuated to -0.704 after addition of the psychosocial factors. The presence of a chronic health condition explained 8.2 % of the variance in work ability. The proportion of explained variance increased after addition of the individual and work conditions with, respectively, 1.8 and 1.4 %. The R-square change after addition of the psychosocial factors in model 4 was 8.5 %, resulting in a total explained variance of 19.7 % in work ability. After adding the perceived health variables, the association between the presence of a chronic health condition and work ability was strongly attenuated (B = -0.049) and ceased to be statistically significant. The total explained variance of work ability of this final model was 40.1 %. Analyses stratified by the presence of a chronic health condition are shown in Table 3. For both workers with and without a chronic health condition, psychosocial factors and perceived health status were associated with work ability. Small, but significant associations with very low B values were found for workers suffering from a chronic health condition for occupation and work type, whereas gender and age were significant individual factors for workers without a chronic health condition. And 42.8 % of the variance in work ability for workers suffering from a chronic health condition was explained by the factors in the model, while these factors explained 28.7 % of the variance for workers without a chronic health condition.

Discussion The presence of a chronic health condition was related to work ability irrespective of work conditions and psychosocial factors among workers aged 45 years and older. The association between the presence of a chronic health condition and work ability substantially changed through the impact of the psychosocial factors. Perceived health status was very strongly related to the presence of a chronic health condition and explained its relation with work ability to a great extent. This is not surprising, taken the fact that subscales of the SF-36 are multi-item scales which assess separate aspects of health, and these can better differentiate in health than a single-item question. Substantial differences in variables associated with work ability for workers with and without a chronic health condition were not found. Psychosocial factors and perceived health status

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123 5,247

n

0.038

0.130§

Education (reference = low)

0.048 -0.049

0.195¥ -0.293¥ -0.011

Occupation: management versus executive

Work type: physical versus mental job demands

Work type: both physical and mental versus mental job demands

Psychosocial factors

0.032

0.115*

Occupation: policy versus executive

-0.003

0.042

0.146§

Occupation: secretary versus executive

Work conditions

0.021

0.064

Gender (reference = male)

0.008

-0.239

0.002

-0.704¥

-0.095

-0.453

0.084

0.014

0.048

0.041

-0.013

-0.006

-0.777

Lower bound

0.074

-0.134

0.306

0.216

0.245

0.218

0.141

0.011

-0.632

Upper bound

0.024

-0.195§

0.084

0.021

0.080

0.008

-0.033

0.021

0.006

0.023

0.027

0.029 0.092*

-0.038 0.087*

-0.017

Betab

5,247

-0.012§

-0.049

Ba

Ba

95 % CI for B

Model 5

5,247

Model 4

Age (year)

Individual characteristics

Presence of a chronic health condition Chronic health condition (reference = no)

8.2

R-square change (%)

Betab

11.3

8.2

Total R-square (%)

1.4

-0.066

Work type: both physical and mental versus mental job demands 1.8

-0.419

Work type: physical versus mental job demands

-0.050

-0.334

-0.013

-0.067

-0.006

0.016

0.020

-0.02

-0.122

Lower bound

0.023

-0.254

0.465

0.253

0.150

0.322

0.204

-0.017

-0.729

Upper bound

0.097

-0.057

0.180

0.109

0.165

0.169

0.155

-0.005

0.024

Upper bound

-0.155

-0.585

0.236

0.042

-0.055

0.139

0.044

-0.033

-0.880

Lower bound

95 % CI for B

95 % CI for B

-0.021

-0.070

0.087 ¥

0.351¥

Occupation: management versus executive

0.068 0.014

0.230

0.041

0.411

0.147§

0.236

0.041 ¥

-0.079

0.124§

-0.273

-0.025¥

-0.805¥

Betab

0.048

0.096

0.140

-0.018

-0.748

Upper bound

Ba

Occupation: policy versus executive

10

0.324

-0.014

-0.035

-0.900

Lower bound

95 % CI for B

Model 3

Occupation: secretary versus executive

Work conditions

Education (reference = low)

¥

0.021

0.063

Gender (reference = male)

Chronic health condition (reference = no) Individual characteristics -0.084

-0.771

Beta

-0.027¥

-0.924

Upper bound

B

b

Age (year)

-0.287

Lower bound

95 % CI for B

a

Model 2

-0.279

-0.848¥

Beta

b

-0.824¥

Presence of a chronic health condition

B

a

Model 1

Table 2 Multivariable association between the presence of a chronic health condition, work conditions, psychosocial factors and perceived health on work ability

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-0.053¥ 0.055¥ -0.006

Co-worker support Community support

Organizational support

¥

8.5 5,247

R-square change (%)

n

b

a

beta standardized regression coefficient

B unstandardized regression coefficient

p \ .01;

40.1

19.7

Total R-square (%)

* p \ .05;

0.010¥

General health

§

0.119

0.003*

Pain

5,247

20.5

0.039

0.017

Vitality

p \ .001

0.048

0.005§

Mental health

¥

0.055

0.002¥

Role limitations from emotional problems

0.176

0.104

0.004¥

Role limitations from physical problems

¥

0.102

-0.024

-0.008* 0.082

-0.011 0.092

-0.041

0.069

0.075

-0.008 0.028¥

-0.028

0.038¥

0.005

¥

Betab

0.007¥

0.003

-0.035 0.064

-0.051

0.090

0.009

Upper bound

Ba

Social functioning

-0.015

-0.070 0.046

-0.085

0.062

0.005

Lower bound

95 % CI for B

Model 5

0.008¥

-0.017

-0.075 0.182

-0.097

0.139

0.105

Beta

b

Physical functioning

Perceived health status

-0.068

Coping: avoidance behaviour

¥

0.007 0.076¥

¥

Coping: active problem-focusing

B

a

Model 4

Work attitude

Table 2 continued

0.007

0.001

0.014

0.002

0.001

0.003

0.005

0.005

-0.016

-0.023 0.020

-0.044

0.025

0.004

Lower bound

95 % CI for B

0.012

0.005

0.021

0.009

0.003

0.005

0.010

0.011

-0.001

0.007 0.036

-0.013

0.050

0.007

Upper bound

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Int Arch Occup Environ Health Table 3 Multivariable association between work conditions, psychosocial factors and perceived health status on work ability for workers with and without a chronic health condition Work ability workers aged 45 years and older Without chronic health condition B

a

Beta

b

With chronic health condition

95 % CI for B Lower bound

Upper bound

Ba

Betab

95 % CI for B Lower bound

Upper bound

Individual characteristics Age (year)

-0.015§

-0.058

-0.023

-0.006

-0.021

-0.023

Gender (reference = male)

0.121§

0.048

0.045

0.198

0.025

0.007

-0.102

0.152

Education (reference = low)

0.071

0.025

-0.017

0.160

0.131

0.035

0.010

0.271

-0.018 0.017

-0.151 -0.049

0.044 0.145

0.294¥ -0.034

0.074 -0.008

0.135 -0.207

0.454 0.140

-0.008

0.007

Work conditions Occupation secretary versus executive Occupation policy versus executive

-0.054 0.048

Occupation management versus executive

0.058

Work type: physical versus mental job demands

-0.097

0.018

-0.047

0.163

0.139

-0.019

-0.259

0.065

-0.331*

Work type: both physical and mental versus mental job demands

0.027

-0.060

0.337

-0.052

-0.581

-0.080

0.017

0.006

-0.068

0.102

0.029

0.008

-0.108

0.166

0.005¥

0.077

0.003

¥

0.007

0.007¥

0.077

0.084

0.003

0.010

0.021

0.049

0.046¥

0.072

0.022

0.070

-0.026

-0.050

0.008

0.005

-0.025

0.033

Psychosocial factors Work attitude Coping: active problem-focusing

0.035

Coping: avoidance behaviour

-0.033¥

-0.057

-0.050

-0.016

Co-worker support

-0.013

-0.021

-0.030

0.005

¥

Community support

0.029

Organizational support Perceived health status

-0.004

Physical functioning Social functioning

-0.021 0.004 §

0.112

0.019

0.038

0.025

-0.012

-0.013

0.006

-0.015*

0.006§

0.053

0.002

0.010

§

0.069

0.002

0.005

0.072

0.009

0.040

-0.039

-0.029

-0.001

0.008¥

0.084

0.004

0.012

0.008

0.008¥

0.114

0.004

0.012

¥

Role limitations from physical problems

¥

0.003

0.075

0.002

0.004

0.005

0.116

0.003

0.006

Role limitations from emotional problems

0.002*

0.048

0.000

0.003

0.003§

0.081

0.001

0.005

Mental health

0.006*

0.057

0.002

0.011

0.005

0.043

-0.001

0.012

Vitality

0.020¥

0.214

0.016

0.023

0.015¥

0.139

0.009

0.021

Pain

0.002

0.024

-0.001

0.005

0.004*

0.048

0.000

0.007

0.008

¥

0.165

0.011

0.019

¥

General health

0.005

Total R-square (%)

28.7

42.8

3,395

1,852

n §

0.065

0.003

0.015

¥

* p \ .05; p \ .01; p \ .001 B unstandardized regression coefficient

a

b

Beta standardized regression coefficient

were most strongly related to work ability for both groups than other variables in our study. As workers with a chronic health condition reported lower mean scores for work ability, these workers might have the most benefit by a policy focussing on enhancing associated variables. The impact of psychosocial factors on the relation between chronic health conditions and work ability can be explained by the fact that these psychosocial factors indirectly influenced both the chronic condition and the work ability. This finding corroborates with the results of the

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previous studies, which found that the strategy to cope with (health) problems was associated with disability and sickness absence (Bussing et al. 2010; Rapp et al. 2000; Schreuder et al. 2011; Slim et al. 2011). Social support has been shown to be relevant predictors with regard to time to return to work for all types of health conditions, and a more positive attitude towards work was related to a better work ability level (Brouwer et al. 2010; Gould and Polvinen 2008). Support at the workplace and in private life was important determinant of improved work functioning in

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previous studies (Karlsson et al. 2010; Sandmark et al. 2009; Seitsamo et al. 2008). One unanticipated finding in this study was that increased co-worker support was negatively related to work ability. This counter-intuitive result on co-worker support might be explained by the fact that the questions about co-worker support measured expectations and incentives of colleagues regarding continuing work due to illness. It might be that what we deemed to be co-worker support was sometimes perceived as social pressure, which results in a negative association with work ability. Moreover, the subscale measuring co-worker support contained two self-constructed questions and with unknown content and construct validity. The impact of work conditions, as operationalized in this study, was very small. This might be explained by the particular choice of work-related factors in our study. Work conditions varying from role ambiguity, physical climate, work schedule, repetitive movements or ergonomic conditions have been shown to be predictors of work ability (van den Berg et al. 2009). The work-related factors we used in this study did not focus on characteristics of work, but were based on work conditions (such as sector, occupation, duration function and shift work). Future research should therefore be aimed at examining the influence of work conditions on the association between the presence of a chronic health condition and work ability. The variables associated with work ability for workers with and without a chronic health condition were similar. However, the health variables and psychosocial factors were more strongly related to work ability for workers suffering from a chronic health condition compared to workers without a chronic health condition. Moreover, the perceived health status was lower for workers with a chronic health condition. These findings suggest that increasing the work ability level for workers suffering from a chronic disease might be achieved by intervening in psychosocial factors and more importantly in perceived health status. To our knowledge, this is the first study to specifically investigate the impact of work conditions, psychosocial factors and perceived health on the association between the presence of a chronic health condition and work ability. Although the Work Ability Questionnaire (WAI) has been used in several studies as the outcome measure to assess work ability, in this study the first item was used. Whereas the total score of the WAI is based on the number of chronic health conditions, it is inaccurate to use the WAI to determine predictors of the association between chronic health conditions and work ability. Therefore, in this study the single-item measure based on the workers’ view of current work ability compared to when it was at its best is used. A strength of the study is that it was based on a considerable sample of workers with various occupational

activities (e.g. heavy physical labour, back office, health care, teaching and cleaning) employed in different companies. The results of the study can therefore be generalized to a large part of the working population of 45 years and older. Previous studies on the association between psychosocial factors and work conditions on work ability have been conducted in specific occupational groups (Plat et al. 2011; Sjogren-Ronka et al. 2002; van den Berg et al. 2008). Moreover, psychosocial factors in earlier studies were often actually work related such as job demands and lack of control. This study assessed psychosocial factors based on individual resources such as coping behaviour, work attitude and perceived support. A limitation of the study was that the cross-sectional design does not permit exploration of causal relationships between the factors on the association between chronic health condition and work ability. Therefore, it remains unknown whether, for example, increased co-worker support was negatively related to work ability or workers with a low work ability receive more social support from co-workers. Nevertheless, the results are still of interest as they provide a first insight into important factors to intervene in work ability among workers aged 45 years and older with or without a chronic health condition. Additional longitudinal (intervention) studies are needed to examine causality. A second limitation concerns the fact that self-report was used to assess all the variables in this study. As a result, some misclassification of respondents might have occurred which will most probably have been non-differential and thus have resulted in underestimations of the associations under study. However, it is known from literature that self-reporting of health status and of certain physical chronic diseases (diabetes, cardiovascular disease and musculoskeletal and respiratory problems) is reasonably reliable (Roskes et al. 2005). Therefore, we do not expect that the self-reporting of health and problems due to ageing introduced any significant bias for this kind of health conditions. Thirdly, we cannot rule out that non-response has influenced our results. The overall response rate of 39 % at baseline was regarded as reasonable for an anonymous survey in the working population. Because of the anonymous study design, we were not able to investigate the characteristics of the non-responders properly. We found that the response rate in large organizations ([4,000 workers) was lower compared to that in the smallest organizations (around 250 workers). Furthermore, we found differences regarding gender (higher percentage response of male workers in production and female in health care and education) and function (more executive workers in production, more policy and management workers in telecommunication and government). This might be explained due to sector differences, for example, more male workers in the production compared to health care and education. Furthermore,

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the results of our study might not be representative for workers in the production sector because of the underrepresentation of these workers in our study. Finally, workers between 45 and 64 years who are still working might be a very select, relatively healthy group of the general population of this age. This is known as the healthy worker effect, a phenomenon which is often encountered in occupational cohorts (Li and Sung 1999; Shah 2009). In this cohort of older workers the healthy worker selection is probably stronger than in populations of workers of all ages, because of many possibilities of early retirement that were available for older workers in the last two decades. Because of that, the results from our study are probably an underestimation of the influence of determinants on the association between the presence of a chronic health condition and work ability. Conclusion and recommendations We found that psychosocial factors and especially perceived health status, rather than work conditions, explain a large part of the decreased work ability of workers with a chronic condition. Variables associated with work ability did not substantially differ for workers with and without a chronic health condition. Based on the lower mean scores for workers with a chronic health condition for work ability as well for predictors, these workers might have the most benefit by a policy focussing on enhancing these associated variables. Given these results, it may be a promising approach to address perceived health as well as psychosocial factors in strategies and interventions towards a sustainable healthy working life. Previous studies found beneficial effects of the problem-solving approach on health- and work-related outcomes (Ayres and Malouff 2007; van der Klink et al. 2003; Vuori et al. 2012). Problem-solving-based interventions might increase the workers’ awareness and behaviour by emphasizing their own decisive role in attaining goals and giving them the feeling that they can be effective in carrying out the necessary actions, with support from others. Future research to determine variables associated with work ability for workers with and without a chronic health condition should incorporate longitudinal designs and also include work characteristics such as physical climate, work posture and work demands, as well as job control, decision authority and work resources. Conflict of interest of interest.

The authors declare that they have no conflict

Ethical standard This study was conducted with the ethical approval of the Medical Ethics Committee of the University Medical Center Groningen, Groningen, The Netherlands.

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