8
ORIGINAL ARTICLE The influence of psychosocial work characteristics on the need for recovery from work: a prospective study among computer workers Ruben A. Kraaijeveld Maaike A. Huysmans Marco J. M. Hoozemans Allard J. Van der Beek Erwin M. Spekle ´ Received: 1 May 2012 / Accepted: 5 February 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Purpose To investigate the influence of high job demands, low job control, and high social support on need for recovery (NFR) among computer workers. Methods Data was obtained from a longitudinal cohort study, including 5 consecutive measurements, with an in-between period of 6 months. General estimating equa- tions analyses were performed to assess the risk for high NFR 6 months later. Odds ratios (ORs) for high NFR were cal- culated for high job demands, low job control and low social support, separately. Likewise, ORs were calculated for combinations of job demands and job control, as well as for combinations of job demands, job control and social support. Results High job demands resulted in an increased risk for high NFR 6 months later, particularly in older workers. Low social support showed also an increased risk for future high NFR, but this was not the case for low job control. Furthermore, a combination of high job demands and low job control, as well as a combination of high job demands, low job control and low social support demonstrated an increased risk for future high NFR where older workers showed higher risks. Conclusion This study demonstrated that adverse psy- chosocial work characteristics predicted future NFR among computer workers. Keywords Need for recovery Á Psychosocial work characteristics Á Computer work Á Job demand-control-support model Introduction Throughout the years, multiple studies have demonstrated that psychosocial work characteristics can play an impor- tant factor in the development of work-related health problems and impaired psychological well-being (Choi et al. 2011; Kuper and Marmot 2003; Netterstrom et al. 2006; van den Heuvel et al. 2005). In most studies, psy- chosocial work characteristics have been described in terms of job demands, job control or decision latitude, and social support. These terms are derived from the job demand-control-support (JDCS) model (Johnson and Hall 1988; Johnson et al. 1989), which is an extension of the earlier postulated job demand-control (JDC) model by Karasek (1979). According to the JDCS model, jobs with high demands, low control and low social support are the most harmful for workers’ health (Johnson and Hall 1988). These jobs have shown to result in an increased risk of several health problems, such as cardiovascular diseases (Netterstrom et al. 2006), depression (Sanne et al. 2005), low back and neck pain (Macfarlane et al. 2009), neck and upper limb symptoms (Bongers et al. 2006) and psycho- logical distress (Choi et al. 2011). R. A. Kraaijeveld Á M. A. Huysmans (&) Á A. J. Van der Beek Department of Public and Occupational Health, EMGO? Institute for Health and Care Research, VU University Medical Center, PO Box 7057, 1007, MB, Amsterdam, The Netherlands e-mail: [email protected] M. A. Huysmans Á M. J. M. Hoozemans Á A. J. Van der Beek Á E. M. Spekle ´ Body@Work, Research Center on Physical Activity, Work and Health, Amsterdam, The Netherlands M. J. M. Hoozemans Á E. M. Spekle ´ Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands E. M. Spekle ´ Arbo Unie OHS, Utrecht, The Netherlands 123 Int Arch Occup Environ Health DOI 10.1007/s00420-013-0852-2

The influence of psychosocial work characteristics on the need for recovery from work: a prospective study among computer workers

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Page 1: The influence of psychosocial work characteristics on the need for recovery from work: a prospective study among computer workers

ORIGINAL ARTICLE

The influence of psychosocial work characteristics on the needfor recovery from work: a prospective study among computerworkers

Ruben A. Kraaijeveld • Maaike A. Huysmans •

Marco J. M. Hoozemans • Allard J. Van der Beek •

Erwin M. Spekle

Received: 1 May 2012 / Accepted: 5 February 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract

Purpose To investigate the influence of high job

demands, low job control, and high social support on need

for recovery (NFR) among computer workers.

Methods Data was obtained from a longitudinal cohort

study, including 5 consecutive measurements, with an

in-between period of 6 months. General estimating equa-

tions analyses were performed to assess the risk for high NFR

6 months later. Odds ratios (ORs) for high NFR were cal-

culated for high job demands, low job control and low social

support, separately. Likewise, ORs were calculated for

combinations of job demands and job control, as well as for

combinations of job demands, job control and social support.

Results High job demands resulted in an increased risk

for high NFR 6 months later, particularly in older workers.

Low social support showed also an increased risk for future

high NFR, but this was not the case for low job control.

Furthermore, a combination of high job demands and low

job control, as well as a combination of high job demands,

low job control and low social support demonstrated an

increased risk for future high NFR where older workers

showed higher risks.

Conclusion This study demonstrated that adverse psy-

chosocial work characteristics predicted future NFR among

computer workers.

Keywords Need for recovery � Psychosocial work

characteristics � Computer work �Job demand-control-support model

Introduction

Throughout the years, multiple studies have demonstrated

that psychosocial work characteristics can play an impor-

tant factor in the development of work-related health

problems and impaired psychological well-being (Choi

et al. 2011; Kuper and Marmot 2003; Netterstrom et al.

2006; van den Heuvel et al. 2005). In most studies, psy-

chosocial work characteristics have been described in

terms of job demands, job control or decision latitude, and

social support. These terms are derived from the job

demand-control-support (JDCS) model (Johnson and Hall

1988; Johnson et al. 1989), which is an extension of the

earlier postulated job demand-control (JDC) model by

Karasek (1979). According to the JDCS model, jobs with

high demands, low control and low social support are the

most harmful for workers’ health (Johnson and Hall 1988).

These jobs have shown to result in an increased risk of

several health problems, such as cardiovascular diseases

(Netterstrom et al. 2006), depression (Sanne et al. 2005),

low back and neck pain (Macfarlane et al. 2009), neck and

upper limb symptoms (Bongers et al. 2006) and psycho-

logical distress (Choi et al. 2011).

R. A. Kraaijeveld � M. A. Huysmans (&) � A. J. Van der Beek

Department of Public and Occupational Health, EMGO?

Institute for Health and Care Research, VU University Medical

Center, PO Box 7057, 1007, MB, Amsterdam, The Netherlands

e-mail: [email protected]

M. A. Huysmans � M. J. M. Hoozemans �A. J. Van der Beek � E. M. Spekle

Body@Work, Research Center on Physical Activity, Work and

Health, Amsterdam, The Netherlands

M. J. M. Hoozemans � E. M. Spekle

Research Institute MOVE, Faculty of Human Movement

Sciences, VU University Amsterdam, Amsterdam, The

Netherlands

E. M. Spekle

Arbo Unie OHS, Utrecht, The Netherlands

123

Int Arch Occup Environ Health

DOI 10.1007/s00420-013-0852-2

Page 2: The influence of psychosocial work characteristics on the need for recovery from work: a prospective study among computer workers

It has been hypothesized that work-related health

problems are preceded by a higher need for recovery

(NFR), which can be seen as an intermediate variable

between psychosocial work characteristics and work-rela-

ted health problems (Sluiter et al. 2003). The concept of

NFR has been deduced from the effort-recuperation model

by Meijman and Mulder (1998) and refers to the extent of

recuperating from work-induced effort. This need for

recovery can be observed particularly during the last hours

of work and immediately after work. It is characterised by

temporary feelings of overload, irritability, social with-

drawal, lack of energy and reduced performance (van

Veldhoven and Broersen 2003).

Different studies have indeed shown that workers with

high NFR are at risk of adverse health effects. Sluiter et al.

(2003) concluded that NFR has a strong prognostic value

regarding subjective health complaints in different occu-

pational groups. A high NFR was also found to be a pre-

dictor for cardiovascular disease in a working population

(van Amelsvoort et al. 2003). Furthermore, Spekle et al.

(2012) found that, of several risk factors, NFR was the

strongest predictor for neck and upper limb symptoms in a

population of computer workers. Finally, in a study by De

Croon et al. (2003), NFR predicted future sickness absence

in truck drivers. Aforementioned studies showed that NFR

can be seen as a precursor of a variety of health problems.

Therefore, monitoring NFR might be useful to early

identify those at risk of work-related health problems.

Only few studies have addressed the relation between

adverse psychosocial work characteristics and NFR. Cross-

sectional studies showed indeed that high job demands, low

control and low social support were associated with high

NFR (Kiss et al. 2008; Sluiter et al. 2001; van der Hulst

et al. 2006). De Raeve et al. (2007) concluded in a pro-

spective study that an increase in job demands, as well as a

decrease in decision latitude, predicted a subsequent

increase in NFR. Another prospective study by Sluiter et al.

(2003) also demonstrated that high job demands predicted

high NFR. However, both of these prospective studies did

not address the influence of combinations of job demands,

job control and social support on future NFR.

Since NFR is a precursor of different work-related

health problems, and little is known about the influence of

combinations of adverse psychosocial work characteristics

on this precursor, more longitudinal research is needed.

Therefore, the aim of the present study was to investigate

the influence of adverse psychosocial work characteristics,

in terms of job demands, job control and social support, on

future NFR. Three main research questions will be

addressed. Firstly, do high job demands, low job control

and low social support separately predict high NFR? Sec-

ondly, does a combination of high job demands and low job

control predict high NFR? Thirdly, does a combination of

high job demands, low job control and low social support

predict high NFR?

Methods

Study design & participants

For this study, data were obtained from a longitudinal cohort

study, with a 24-months follow-up, which was set-up to

investigate the predictive validity of a questionnaire with

respect to neck and upper limb symptoms in computer

workers (Spekle et al. 2012). From 2004 until 2006, com-

puter workers of a Dutch occupational health service were

contacted per e-mail 5 times consecutively, with an

in-between period of 6 months, for filling out an internet-

based questionnaire. The population consisted of office staff

(45 %), occupational health physicians (20 %), health care

professionals & consultants (25 %) and managers (10 %),

who all used a computer for at least 2 h a day. The educa-

tional level of this population was primarily intermediate to

higher vocational or university education. The study design,

protocols, procedures and informed consent form of the

study were approved by the Ethics Committee of the Faculty

of Human Movements Sciences of the VU University

Amsterdam, and all participants electronically provided

informed consent before filling out the questionnaire.

Assessment of psychosocial work characteristics

and NFR

The internet-based questionnaire primarily concerned

exposure to risk factors for neck, shoulder and arm

symptoms (Spekle et al. 2009). For developing this ques-

tionnaire, the JDCS model was used as a theoretical

framework and questions were constructed or based on a

literature review on risk factors for neck and upper limb

symptoms. Furthermore, a substantial part of the questions

on psychosocial work characteristics was derived from the

Dutch Musculoskeletal Questionnaire (Hildebrandt et al.

2001) with response categories limited to ‘yes’ or ‘no’,

instead of the usually used Job Content Questionnaire of

Karasek (1979) which uses a four-point Likert scale. The

psychometric properties of the questionnaire used in the

present study were previously tested and results indicated

an acceptable reliability, concurrent validity and homoge-

neity (Spekle et al. 2009).

Variables of interest were obtained from the psychoso-

cial work characteristics scales of this questionnaire. The

scales ‘recovery time’, ‘work pace and load’, ‘decision

latitude’ and ‘work relations’ were used to asses NFR, job

demands, job control and social support, respectively

(https://www.rsiquickscan.com/research/questionnaire.pdf).

Int Arch Occup Environ Health

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The ‘recovery time’ scale consisted of 6 items such as ‘do you

feel mentally exhausted by your work?’ and ‘do you feel at the

end of your tether?’ Responses (‘yes’ or ‘no’) to items were

summed up to a total score of a maximum of 6, where a higher

score meant more recovery is needed. Although this scale has

not been widely used for assessing NFR, items represent

fatigue effects of work-induced efforts. In addition, items of

this scale are similar to the items of the exhaustion scale of the

Maslach Burnout Inventory-General Survey (MBI-GS)

(Schaufeli et al. 1996) and the ‘need for recovery scale’ from

the Dutch Questionnaire on the Experience and Evaluation of

Work [(Dutch abbreviation: VBBA (van Veldhoven and

Broersen 2003))]. In previous studies, our NFR scale was

found to be internally consistent, reliable and showed pre-

dictive validity with respect to arm, shoulder and neck

symptoms (Spekle et al. 2009, 2012).

The ‘work pace and load’ scale consisted of 8 items with

questions, such as ‘do you regularly work under time

pressure?’ and ‘is your work often too tiring for you?’ The

‘decision latitude’ scale consisted of 9 items with ques-

tions, such as ‘can you choose when you take breaks?’ and

‘do you decide yourself when you carry out a task?’ Fur-

thermore, ‘work relations’ is a 7-item scale, with questions,

such as ‘do you find the general atmosphere at work good?’

and ‘does your direct supervisor support you enough in

your work?’ Responses (‘yes’ or ‘no’) to the items were

summed up to generate a total score for ‘work pace and

load’, ‘decision latitude’ and ‘work relations’, ranging

from 0 to 8, 9 and 7, respectively. All items were asked or

recoded in such a way that a higher score meant an unfa-

vourable psychosocial work characteristic. In addition, the

questionnaire contained also questions about gender, age,

prevalence of neck and upper limb symptoms, working

hours, work posture and movements, work tasks, work

environment factors, furniture, computer work station

attributes, and eyesight.

Statistical analyses

To investigate the influence of adverse psychosocial work

characteristics on future NFR, generalized estimating

equations (GEE) analyses were performed. With these

analyses, the relation between longitudinally measured

variables can be estimated using all longitudinal data

simultaneously while adjusting for within-person correla-

tions caused by repeated measurements on each subject

(Twisk et al. 2005). In addition, data of all five measure-

ments are used for these analyses. This means that data of

the present study yielded 4 times the relation between

psychosocial work characteristics and NFR (Table 1).

Scale scores of the questionnaire were inverted into

binominal variables with scores above the 67th percentile

of the population as cut-off point for high NFR, high job

demands, low job control and low social support, as well as

for the other continuous risk variables, which were treated

as possible confounders. This meant for NFR that a par-

ticipant had to agree on at least 2 items of this scale to be

defined as having a ‘high NFR’. All other cut-off values

can be found in Table 2. For the GEE analyses, a time lag

of 6 months was used, so that the psychosocial work

characteristics and ‘baseline’ NFR were assessed 6 months

prior to the outcome NFR. To prevent reversed causation,

participants with a high NFR at ‘‘baseline’’ for each of the

4 relations between psychosocial work characteristics and

NFR were excluded for that particular relation (Table 1).

Participants excluded for one of the time cohorts could be

part of the other time cohorts, as long as their NFR for that

particular ‘‘baseline’’ was low (NFR was 0 or 1).

Firstly, crude odds ratios (ORs) for the risk of high NFR

were calculated for high job demands, low job control and

low social support, separately. Secondly, crude ORs were

calculated for combinations of job demands and job control,

with the combination of low job demands and high job

control taken as reference. Thirdly, crude ORs were cal-

culated for combinations of job demands, job control and

social support, with the combination of low job demands,

high job control and high social support as reference.

Fourthly, tests for effect modification by gender and age for

all analyses were carried out, as well as statistical tests for

interaction effects of aforementioned combinations. A

binominal variable of age, with the median score as cut-off

point, appeared to be an effect modifier for the influence of

high job demands and aforementioned combinations on

NFR. Analyses for job demands and aforementioned com-

binations were performed again after stratification for age;

resulting in ORs for younger (age B 43 years) and older

workers (age [ 43 years). Finally, all ORs were adjusted

for confounding variables by multiple GEE analyses.

Potential confounding variables were included if those

variables modified the regression coefficients of the vari-

ables and combinations of interest more than 10 %. In all

aforementioned analyses, there was a correction for time of

measurement. Analyses were performed using SPSS 17.0.

Results

The time line of measurements and sample sizes are pre-

sented in Table 1. After each measurement, workers could

enter or withdraw from the study. At the first measurement,

2,039 out of 3,383 workers (response rate = 60 %) filled

out the questionnaire, at the second 1,478 out of 3,019

(response rate = 49 %), at the third 1,259 out of 2,817

(response rate = 45 %), at the fourth 1,189 out of 2,669

(response rate = 45 %) and at the fifth 1,042 out of 2,485

(response rate = 42 %). Only data of two or more

Int Arch Occup Environ Health

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consecutive measurements of one subject were used, and

this resulted in a total population of 1,531 workers (34 %

males, mean age (SD) = 43 (9) years, 63.1 % working

more than 30 h per week, 72 % working more than 4 h per

day with a computer). After excluding workers with high

NFR at ‘baseline’, analyses were performed on data of at

least 1,215 workers.

The influence of job demands, job control and social

support on NFR, separately, is presented in Table 2. The

influence of job demands is presented for two age groups,

because age appeared to be an effect modifier for the

influence of job demands, which was not the case for job

control and social support. In both age groups, high job

demands resulted in a significantly higher risk for high

NFR 6 months later, where older workers showed the

highest risks. The adjusted OR for the group of 43 years

and younger was 1.7 (95 % CI: 1.2–2.3), and the adjusted

OR for the group of 44 years and older was 2.9 (95 % CI:

2.1–3.9). In both age groups, low social support demon-

strated significantly higher risks for future high NFR, as

well. The adjusted OR for low social support was 1.9

(95 % CI: 1.5–2.3). Low job control also showed higher

risks for future high NFR in the total population, but this

was not statistically significant after adjusting for con-

founding variables.

The influence of combinations of job demands, job

control and social support is presented for the younger

workers in Table 3 and for the older workers in Table 4.

Firstly, in both age groups, the combination of high job

demands and low job control resulted in significantly

higher risks for future high NFR, where older workers

showed the highest risks. The adjusted OR for the group of

43 years and younger was 1.6 (95 % CI: 1.0–1.7), and the

adjusted OR for the group of 44 years and older was 4.8

(95 % CI: 3.0–7.8).

Secondly, the combination of high job demands, low job

control and low social support demonstrated significantly

higher risks for future high NFR as well, particularly in

older workers. The adjusted OR for the group of 43 years

and younger was 2.2 (95 % CI: 1.0–5.0), and the adjusted

OR for the group of 44 years and older was 7.7 (3.8–15.5).

Noteworthy is that in both age groups there were no

statistically significant interactions observed, neither for

job demands with job control, nor for job demands with job

control and social support (results not shown).

Discussion

The present study investigated, in a population of computer

workers, the influence of adverse psychosocial work

characteristics, in terms of job demands, job control and

social support, on NFR 6 months later. Results demon-

strated adverse effects of high job demands and low social

support on future NFR but did not show an effect of low

job control on future NFR. Furthermore, a combination of

Table 1 Time line of measurements (T1-T5) and sample sizes (N)

T=1 (N=2039) T=2 (N=1478) T=3 (N=1259) T=4 (N=1189) T=5 (N=1042)

0 months 6 months 12 months 18 months 24 months

Job demands

Job control

Social support

Job demands

Job control

Social support

Job demands

Job control

Social support

Job demands

Job control

Social support

Job demands

Job control

Social support

NFR NFR NFR NFR NFR

(N=1225)a

N=823b(N=1019)a

N=698b(N=803)a

N=524b(N=827)a

N=533b

The influence of job demands, job control and social support on the need for recovery (NFR) 6 months latera Indicates the number of participants for whom data was available for two consecutive measurementsb The actual number of participants in the analyses, that is, those for whom data was available for two consecutive measurements and had a low

NFR at ‘‘baseline’’ (NFR \ 2)

Int Arch Occup Environ Health

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Page 5: The influence of psychosocial work characteristics on the need for recovery from work: a prospective study among computer workers

high job demands and low job control as well as a com-

bination of high job demands, low job control and low

social support resulted in an increased risk for high NFR

6 months later. Age modified the adverse effects of high

job demands and aforementioned combinations on NFR;

computer workers of 44 years and older showed higher

risks for high NFR than younger workers. Contrarily,

comprehensive reviews on the JDCS model in relation to

psychosocial well-being did not address any effect modi-

fication by age, in case of adverse psychosocial work

characteristics (Hausser et al. 2010; van der Doef and Maes

1999).

The adverse effects of high job demands and low social

support separately and combined are in line with earlier

studies regarding the influence of psychosocial work

characteristics on mental health outcomes (Choi et al.

2011; de Raeve et al. 2007; Netterstrom et al. 2006; Sluiter

et al. 2003). The most striking finding of this study was that

there was hardly any influence of job control on future

NFR. The lack of influence of job control on NFR in this

study contradicts results of earlier studies on psychosocial

work characteristics and mental health (Dalgard et al.

2009; de Raeve et al. 2007; Sanne et al. 2005). This might

be due to the scale that was used to asses job control; it

contained solely items concerning decision authority and

no items about skill discretion, which were applied in

scales in earlier studies (Dalgard et al. 2009; de Raeve et al.

2007; Sanne et al. 2005). Moreover, it should be noted that

selection bias might have contributed to these study results

as well, as will be explained later on.

Table 2 Odds ratios (ORs) of GEE analyses for Need for Recovery (NFR)

N and observations (O) Risk

level

Observations

(% of O)

NFR 6 months later (high NFR C 2)

OR crude

(95 % CI)

OR adjusted

(95 % CI)

Job demands (JD): 0–8 N = 1250, O = 2592 Age B 43 years Low: 0–4 969 (37 %) 1 1

High: 5–8 322 (12 %) 1.7 (1.2–2.3)* 1.7 (1.2–2.3)a*

Age [ 43 years Low: 0–4 945 (36 %) 1 1

High: 5–8 356 (14 %) 2.9 (2.1–3.9)* 2.9 (2.1–3.9)a*

Job Control (JC): 0–9 N = 1217, O = 2396 High: 0–2 1716 (72 %) 1 1

Low: 3–9 680 (28 %) 1.3 (1.0–1.6)** 1.1 (0.9–1.5)b

Social support (SS): 0–7 N = 1250, O = 2592 High: 0–2 1943 (75 %) 1 1

Low: 3–7 649 (25 %) 1.9 (1.5–2.3)* 1.9 (1.5–2.3)a*

* Significant at p \ .01, ** significant at p \ .05a No confounders were foundb Adjusted for social support, work tasks and neck and upper limb symptoms

Table 3 Odds ratios (ORs) of GEE analyses for Need for Recovery (NFR) of younger workers (age B 43 years)

N and observations (O) Job type Observations (% of O) NFR 6 months later (high NFR C 2)

OR crude (95 % CI) OR adjusted (95 % CI)

Job demands (JD) &

Job control (JC)

N = 614, O = 1199

Low JD\high JC 675 (56 %) 1 1

Low JD\low JC 224 (19 %) 1.0 (0.6–1.5) 0.9 (0.6–1.3)a

High JD\high JC 208 (17 %) 1.7 (1.1–2.4)* 1.6 (1.0–2.4)a**

High JD\low JC 92 (8 %) 1.9 (1.2–3.1)* 1.6 (1.1–2.4)a**

Job demands (JD) &

Job control (JC) &

Social Support (SS) N = 614, O = 1199

Low JD\high JC\high SS 521 (43 %) 1 1

Low JD\high JC\low SS 154 (13 %) 1.7 (1.1–2.6)** 1.6 (1.0–2.5)a**

Low JD\low JC\high SS 166 (14 %) 0.8 (0.5–1.4) 0.7 (0.4–1.3)a

Low JD\low JC\low SS 58 (5 %) 2.1 (1.1–4.0)** 1.8 (1.0–3.4)a

High JD\high JC\high SS 158 (13 %) 1.6 (1.1–2.6)** 1.6 (1.0–2.5)a**

High JD\high JC\low SS 50 (4 %) 2.8 (1.5–5.3)* 2.8 (1.5–5.3)a*

High JD\low JC\high SS 64 (5 %) 2. 0 (1.1–3.7)** 1.7 (0.9–3.1)a

High JD\low JC\low SS 28 (2 %) 2.7 (1.3–5.7)* 2.2 (1.0–5.0)a**

* Significant at p \ .01, ** significant at p \ .05a Adjusted for neck and upper limb symptoms

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Because there was no impact of low job control on

future NFR in this study, the influence of job control in

case of high job demands was further investigated.

According to the strain hypothesis of the JDCS model, jobs

with high demands and low control are the most harmful

for workers’ health (Johnson and Hall 1988). Furthermore,

the buffer hypothesis of this model states that high job

control can moderate the negative impact of high job

demands (Hausser et al. 2010; Johnson and Hall 1988).

Additional analyses of a group with high job demands in

combination with high and low job control demonstrated a

significantly increased risk for high NFR 6 months later in

case of low job control. However, there was no interaction

between high job demands and job control. Therefore,

results corroborated the strain hypothesis of the JDCS

model but did not confirm the buffer hypothesis. Hausser

et al. (2010) defined buffering explicitly as attenuation due

to an interaction effect.

Effect modification by age for the influence of adverse

psychosocial work characteristics on psychological well-

being is seldom reported. Nevertheless, a decline in the

work ability of the ageing worker could explain the higher

risks found in older workers in this study. Ilmarinen et al.

(1997) reported in a comprehensive follow-up study that

the work ability, measured by the work ability index,

declined significantly among workers, aged 45 years and

older, who continued working for a period of 11 years. In

addition, older workers seem to be more susceptible for

developing higher levels of NFR; different studies showed

that older workers (age [ 45 years) have a higher NFR

(Kiss et al. 2008; Mohren et al. 2010).

Noteworthy is that the results from the present study

seemed to be quite robust, since changing the cut-off value

for a high NFR to three or higher led to the same results,

that is, similar or slightly lower Odds Ratios for job

demands, job control and social support.

Strengths & limitations of the study

Strength of this study is that the time-varying nature of

both psychosocial work characteristics and psychological

well-being was taken into account. All study variables were

assessed consecutively 5 times over a period of 2 years,

which fortified results. Edwards (2008) argued that longi-

tudinal research should incorporate more time lags between

exposure and outcome to strengthen the ability to draw

causal inferences. For analyses, a time lag of 6 months was

used between exposure and onset of symptoms. Additional

analyses (results not shown) demonstrated that a time lag

of 6 months resulted in the strongest relations between the

psychosocial work characteristics and NFR as compared to

time lags of 12 or 18 months. Likewise, De Raeve et al.

(2007) argued that time lags between work characteristics

and mental health should not be longer than 1 year,

because of the time-varying nature of work characteristics.

With respect to the internal validity of the study results,

different types of potential bias are worth noting. Firstly,

selection bias may have played a role, although it is diffi-

cult to determine the impact of this type of bias, because

workers could enter, withdraw or re-enter at each time

point. However, to get some insight into selection bias, the

obtained study variables, from the questionnaire of the

participants who participated at T = 1 and T = 2, were

compared to those who participated at T = 1, but not at

T = 2. Indeed, there were some differences between those

two groups. The group of participants who did not fill out

Table 4 Odds ratios (ORs) of GEE analyses for need for recovery (NFR) of older workers (age [ 43 years)

N and observations (O) Job type Observations (% of O) NFR 6 months later (high NFR C 2)

OR crude (95 % CI) OR adjusted (95 % CI)

Job demands (JD) &

Job control (JC)

N = 602, O = 1196

Low JD\high JC 600 (50 %) 1 1

Low JD\low JC 272 (23 %) 1.4 (0.9–2.1) 1.3 (0.9–2.0)a

High JD\high JC 233 (19 %) 2.6 (1.8–4.0)* 2.6 (1.8–3.9)a*

High JD\low JC 91 (8 %) 5.3 (3.4–8.4)* 4.8 (3.0–7.8)a*

Job demands (JD) &

Job control (JC) &

Social Support (SS) N = 601, O = 1195

Low JD\high JC\high SS 458 (38 %) 1 1

Low JD\high JC\low SS 142 (12 %) 1.6 (1.0–2.7) 1.6 (1.0–2.8)a

Low JD\low JC\high SS 198 (17 %) 1.4 (0.9–2.3) 1.4 (0.8–2.2)a

Low JD\low JC\low SS 74 (6 %) 2.1 (1.1–3.9)** 2.0 (1.0–3.8)a**

High JD\high JC\high SS 180 (15 %) 2.3 (1.4–3.7)* 2.3 (1.4–3.7)a*

High JD\high JC\low SS 52 (4 %) 6.2 (3.3–11.4)* 5.8 (3.1–10.8)a*

High JD\low JC\high SS 55 (5 %) 4.8 (2.6–8.9)* 4.5 (2.3–8.5)a*

High JD\low JC\low SS 36 (3 %) 8.8 (4.5–17.4)* 7.7 (3.8–15.5)a*

* Significant at p \ .01, ** significant at p \ .05a Adjusted for neck and upper limb symptoms

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the questionnaire at T = 2 (but might have entered the

study again at e.g. T = 4) had a significantly higher

prevalence of low job control, low social support and high

monotonous work. There were no age or gender differ-

ences. Taking into account the difference between both

groups for job control, selection bias could have changed

the influence of job control on NFR, since participants with

low job control at T = 1 withdrew themselves more often.

Secondly, self-report bias may have influenced the

results, because study variables were obtained from survey

data using self-report measures. However, a study by

Griffin et al. (2007) showed that there was no difference

between self-reported or observed job control in relation to

depression and anxiety symptoms. Moreover, a study by

Sluiter et al. (2001) showed that self-reported NFR, using

the ‘Need for recovery scale’ developed by (van Veldhoven

and Broersen 2003), was associated with objectively

assessed physiological measures of participants, such as

cortisol and adrenaline levels. Thus, NFR, as perceived by a

worker, can be a valid indicator of psychophysiological

recovery after work. Thirdly, feedback bias might have

played a role as well; this implies that earlier outcomes may

affect subsequent exposures. As explained by Eisen (1999),

the GEE method cannot control for this bias. In favour of

the present study was that feedback bias was minimized as

much as possible by excluding participants with high NFR

at ‘baseline’, and exposure and outcome variables were

assessed at different time points.

Practical implications

Results demonstrated that high job demands can be

harmful for worker’s psychological well-being, particularly

in older workers, and results also showed that high job

control did not attenuate the negative impact of high job

demands. However, evidence-based interventions to reduce

job demands at the workplace are scarce. Interventions that

are frequently used are courses aimed at improving time

management skills and handling stress in the workplace

(https://www.rsiquickscan.com/research/interventions.pdf).

Promising moderators, which might buffer the negative

impact of high job demands, are psychological detach-

ment and other recovery experiences, as introduced by

Sonnentag and Fritz (2007). Psychological detachment

means to disengage oneself mentally from work during off-

job time (Sonnentag and Fritz 2007). It has been argued

that the lack of recovery could have even more impact on

workers’ well-being than job strain itself (Lundberg 2005;

Sonnentag and Zijlstra 2006). A quasi-experimental study

by Hahn et al. (2011) already indicated that a training

program on recovery experiences resulted in a decrease of

perceived stress and state negative effect of participants.

However, prevention efforts should not be limited to

self-management. It is the organisation that creates the

stress, and, therefore, the prevention and management of

workplace stress should primarily consist of organisational

level interventions. In this regard, Michie (2002) gave

several useful examples of possible interventions strate-

gies, where the emphasis is on the organisation, rather than

the individual, such as giving employees the opportunity to

participate in the design of his/her own work situation,

adapt working conditions to people’s differing physical and

mental attitudes and limit or avoid closely controlled or

restricted work.

The present results apply to a source population of

computer workers of a Dutch Occupational Health Service,

with a relatively large variety of job titles. The majority of

these workers were primarily engaged in administrative

work, and all workers, including the health care profes-

sionals, had a substantial amount of computer work per day

(all of them worked at least 2 h per day with a computer

and 72 % even more than 4 h per day). Even though, we

realize that there are clear organisational differences

between the different occupations in this population, we

argue that this is typical for a group computer workers.

Therefore, we consider this population to be representative

of computer workers in general. However, it is recom-

mended in future research to further investigate the effects

of job demands, job control and social support in other

populations of computer workers, and then focus specifi-

cally on differences between younger and older workers.

Conclusion

This study demonstrated, in a population of computer

workers, that high job demands predicted high NFR

6 months later, and this relation was more pronounced in

older workers. Low social support predicted future high

NFR as well, but this was not the case for low job control.

Furthermore, a combination of high job demands and low

job control as well as a combination of high job demands,

low job control and low social support resulted in an

increased risk for future high NFR, where older workers

showed higher risks.

Conflict of interest The authors declare that they have no conflict

of interest.

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