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Mechanical injury and psychosocial factors in the work place predict the onset of widespread body painA two-year prospective study among cohorts of newly employed workers.

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ARTHRITIS & RHEUMATISM
Vol. 50, No. 5, May 2004, pp 1655–1664
DOI 10.1002/art.20258
© 2004, American College of Rheumatology
Mechanical Injury and Psychosocial Factors in the Work Place
Predict the Onset of Widespread Body Pain
A Two-Year Prospective Study Among Cohorts of Newly Employed Workers
Elaine F. Harkness, Gary J. Macfarlane, Elizabeth Nahit, Alan J. Silman, and John McBeth
lifting >24 lbs with 2 hands, pulling >56 lbs, prolonged
squatting, and prolonged working with hands at or
above shoulder level. Of the psychosocial exposures,
those who reported low job satisfaction, low social
support, and monotonous work had an increased risk of
new-onset widespread pain. In multivariate analysis,
monotonous work and low social support were found to
be the strongest independent predictors of symptom
onset.
Conclusion. Our findings demonstrate that the
prevalence of new-onset widespread pain was high, but
among this young, newly employed work force, both
physical and psychosocial factors played an important
role.
Objective. Mechanical injury has been postulated
as a risk factor for widespread pain, although to date,
the evidence is weak. The aim of this study was to
determine whether repeated exposure to mechanical
trauma in the work place predicts the onset of widespread pain and to determine the relative contribution
of mechanical trauma compared with psychosocial factors.
Methods. In this prospective cohort study of 1,081
newly employed subjects in 12 diverse occupational
settings, we collected detailed information on mechanical exposure, posture, physical environment, and psychosocial risk factors in the work place. Study questionnaires were completed at baseline and at 12 and 24
months. Individuals free of widespread pain at baseline
and 12 months were eligible for followup. Generalized
estimating equations were used to determine which
factors predicted the new onset of widespread pain.
Results. Of the 1,081 baseline respondents, 896
were free of widespread pain and were eligible for
further study. Of these 896 subjects, 708 and 520
responded at 12 months and 24 months, respectively.
The rates of new-onset widespread pain were 15% at 12
months and 12% at 24 months. Several work place
mechanical and posture exposures predicted the new
onset of widespread pain: lifting >15 lbs with 1 hand,
Chronic, unexplained widespread pain is the clinical hallmark of the fibromyalgia syndrome. Adverse
psychosocial factors, aspects of health beliefs and behavior, and a history of reporting somatic symptoms have
been shown to predict the new onset of chronic widespread pain in the general population (1). It has also
been hypothesized that physical trauma may be an
important risk factor for widespread pain (2). Such
trauma may occur as a result of, for example, a road
traffic accident or a work place accident. Previous
studies have shown an association between major physical trauma and the onset of fibromyalgia (3,4). For
example, Al Allaf et al (3) found that prior traumatic
events were reported more commonly in patients with
fibromyalgia than in age- and sex-matched controls
(39% and 24%, respectively).
In contrast, the role of low-level physical trauma,
which may occur by repeated exposure, for example,
through manual handling activities within the work
place, is unknown. Only 1 study has examined any
Supported by the British Occupational Health Research
Foundation and the Arthritis Research Campaign, Chesterfield, UK.
Elaine F. Harkness, MSc, Gary J. Macfarlane, MD, Elizabeth
Nahit, PhD, Alan J. Silman, MD, John McBeth, PhD: University of
Manchester, Manchester, UK.
Address correspondence and reprint requests to Elaine F.
Harkness, MSc, ARC Epidemiology Unit, Medical School, University
of Manchester, Oxford Road, Manchester, M13 9PT, UK. E-mail:
moeyjefh@fs1.ser.man.ac.uk.
Submitted for publication May 27, 2003; accepted in revised
form February 10, 2004.
1655
1656
HARKNESS ET AL
aspects of work-related risk factors and chronic widespread pain (5). That study found the prevalence of
fibromyalgia to be increased in subjects who reported
high levels of “physical work stress.” No associations
were found for “mental work stress.” However, that
study was cross-sectional, and other aspects of the work
place environment were not considered.
Recently, we reported that the role of workrelated risk factors in predicting chronic widespread
pain in an unselected population sample was limited (6).
However, that conclusion may have been influenced by
the “healthy worker effect.” The majority of subjects had
been in the same employment for at least 3 years and
were therefore likely to have been well-established
within the work force. As a consequence, we may have
underestimated the true effect of work-related risk
factors and the new onset of widespread pain, since
some individuals may have previously left the work force
as a result of their pain. The aim of the present study was
to examine the effect of work-related risk factors as
predictors of new-onset widespread pain within a cohort
of newly employed workers.
SUBJECTS AND METHODS
Study design. This was a prospective cohort study of
newly employed workers. At baseline, subjects completed a
questionnaire that ascertained current pain status and measured various aspects of work-related mechanical, psychosocial, and environmental risk factors. Subjects who were free of
widespread pain at baseline were identified and were sent
followup questionnaires at 12 months and 24 months to
ascertain whether there was new onset of widespread pain.
Study subjects. The study population has been described in detail elsewhere (7). Briefly, newly employed workers from a range of 12 occupational settings were recruited.
Work places were identified through a number of means,
including newspapers, television reports, job centers, and
contacts through the principal investigators or other work
places. Occupations were chosen to include a large proportion
of subjects who were taking up full-time employment for the
first time (46%). Furthermore, occupations for which high
prevalence rates of musculoskeletal pain had previously been
reported were selected. Subjects engaged in these occupations
were identified from a number of sources (see Appendix A,
available on the Arthritis & Rheumatism Web site at http://
www.interscience.wiley.com/pages/0004-3591/suppmat/
index.html).
Baseline information. Baseline information was collected by means of a self-administered questionnaire. The
majority of workers were contacted in person, either in groups
or individually, and were asked to complete the questionnaire,
which included information across the following 4 domains:
manual handling activities, posture and repetitive movements,
psychosocial factors, and environmental factors.
Manual handling activities. Individuals were asked
about several manual handling activities they had performed
during the last working day. These included lifting weights with
1 hand, lifting weights with 2 hands, carrying weights on 1
shoulder, lifting weights at or above shoulder level, and
pushing or pulling weights. Subjects were asked to estimate
(with the use of a guide) the weights they had lifted and the
duration of each task (in minutes). These questions had
previously been validated by comparing the responses on
self-administered questionnaires with the responses taken
through direct observation techniques (8).
Posture and repetitive movements. Questions on postures and repetitive movements were based on the same
validated instrument (8). Questions were based on postures
and repetitive movements adopted during the last working day
and the amount of time that was spent in each position.
Postures included sitting, standing, kneeling, squatting, working with hands at or above shoulder level, stretching below
knee level, and driving. Repetitive movements included actions
of the arms and wrists.
Psychosocial factors. Work-related psychosocial factors
were assessed by asking individuals about their job demands,
job control, and social support, all of which were based on the
Job Strain model described by Karasek (9), using questions
previously studied in relation to musculoskeletal disorders
(10,11). In that model, subjects with high job demands, little
control over their work, and low social support from colleagues
and supervisors are at potentially high risk of having poor
health outcomes (12). Job demands included questions about
the work pace, stress/worry, and whether individuals found
their work to be monotonous or boring. Job control included
questions on whether individuals thought they could make
their own decisions within the work place and whether they
thought they had the opportunity to learn new things at work.
Subjects were also asked about social support from their
colleagues as well as their overall job satisfaction. The General
Health Questionnaire (GHQ), which has previously been
validated in a number of settings, was included as a measure of
individual psychological distress (13).
Environmental factors. To assess work place environmental factors, individuals were asked whether they had
worked in very hot, cold, or damp conditions during the last
working day.
Pain status. Pain status was assessed by asking individuals the following question, “Thinking back over the past
month, have you had any ache or pain which has lasted for one
day or longer?” If subjects responded affirmatively, they were
asked to indicate on a line drawing of the body any site of such
pain. The “pain drawings” used to determine pain status were
coded in a blinded manner (with regard to all baseline
information) according to the American College of Rheumatology (ACR) definition of widespread pain that was used in
the criteria for fibromyalgia (14). That is, subjects with contralateral pain and pain in the axial skeleton were classified as
having widespread pain.
Followup. Subjects who were free of widespread pain
at baseline were eligible for followup at 12 and 24 months. At
followup, questionnaires were mailed to the study participants.
Up to 2 reminders were sent to those who did not respond.
Pain status at followup was assessed in the same way as at
PREDICTORS OF NEW-ONSET PAIN IN NEWLY EMPLOYED WORKERS
baseline. In addition, individuals were asked whether they had
changed their job and, if so, whether this job change was
because of aches and pains.
Analysis. For the purpose of analysis, exposure variables were categorized as follows. For manual handling activities, the referent group consisted of subjects who did not
perform these activities. The remaining subjects were dichotomized according to the midpoint of the average amount of
weight that was lifted during the last working day. For postures
and repetitive movements, the referent group consisted of
subjects who did not adopt these postures or repetitive movements. The remaining subjects were dichotomized (or were
split into 3 groups) on the basis of categories of time spent in
each position.
For psychosocial factors, subjects were dichotomized
by collapsing the categorical scales into those with low exposure (referent group) and those with high exposure (comparison group). For environmental factors, subjects were dichotomized into those who did not work in these conditions
(referent group) and those who did (comparison group). For
the GHQ, the referent group consisted of subjects who scored
1657
zero. The remaining subjects were dichotomized according to
the midpoint of the distribution of the GHQ scores.
The study included repeated measures of exposures
and outcomes and, hence, was subject to within-subject correlation. Generalized estimating equations were used to assess
predictors of new-onset widespread pain at followup in order
to take into account the repeated measures (15). As a result,
one summary measure is obtained for the relationship between
baseline exposures and outcome at 12 months, and exposures
at 12 months and outcome at 24 months. The results are
expressed as odds ratios (ORs) with 95% confidence intervals
(95% CIs), adjusted for age, sex, and occupational group.
To identify factors that best predicted the new onset of
symptoms, the analysis was conducted in the following way.
First, univariate associations were assessed for each potential
risk factor, adjusting for age, sex, and occupational group.
Second, to identify factors that predicted the new onset of
widespread pain within each domain, multivariate models were
constructed for each separate domain. Where 2 variables were
strongly correlated, those with the stronger point estimate in
the univariate analysis were included in the domain-specific
models. Third, a final multivariate model was constructed by
including factors from the individual domain-specific models
that were considered biologically plausible, were statistically
significant, and the OR was ⱖ1.5 or was ⬍0.67.
Each predictor variable in the final multivariate model
was examined for interactions with the followup period and
within specific domains. Interactions were included in the final
model if they were considered to be biologically plausible, they
were statistically significant, the OR was ⱖ1.5 or was ⱕ0.67,
and they contributed significantly to the final model.
All analyses were conducted using the Stata statistical
package (version 7.0; Stata, College Station, TX).
RESULTS
Figure 1. Distribution of subjects in the study of new-onset widespread body pain in newly employed workers. Newly employed workers were identified from 12 sources and invited to participate in the
study. Subjects were asked to complete a questionnaire at baseline, 12
months (followup 1), and 24 months (followup 2).
Prevalence of widespread pain. Figure 1 shows
the distribution of subjects and the rates of new-onset
widespread pain from baseline through to the second
followup at 24 months. Approximately one-third of the
study population were men. The median age of subjects
who were eligible for followup at 12 months was 23 years
(interquartile range 20–28 years). At baseline, 167 individuals reported widespread pain (15% prevalence; 18%
in men, 11% in women) (P ⫽ 0.007). In a further 18
subjects, pain status was undetermined. Thus, 896 subjects (83%) were eligible for followup.
Over all occupational groups, the followup rates
at 12 and 24 months were 79% and 87%, respectively
(Figure 1). Complete information on pain status was
available for 703 (78%) and 476 (79%) subjects at 12
and 24 months, respectively (Table 1). There was wide
variation in the rates of new-onset widespread pain by
occupational group. At 12 months, symptom onset was
lowest among postal workers (6%) increasing to ⬎30%
in podiatrists and the army infantry; however, the prev-
1658
HARKNESS ET AL
Table 1. Participation and rates of new-onset widespread pain, by followup period
12-month followup
24-month followup
Occupation
No. of
eligible
subjects
Response rate,
no. (%)*
Prevalence rate,
no. (%)
Response rate,
no. (%)*
Prevalence rate,
no. (%)
Firefighter
Police officer
Army officer
Army infantry
Army clerk
Dentist
Podiatrist
Nurse
Forestry worker
Retail worker
Postal worker
Shipbuilder
Total
139
41
75
59
62
92
68
77
28
98
61
96
896
120 (86)
36 (88)
50 (67)
27 (46)
54 (87)
69 (75)
53 (78)
61 (79)
20 (71)
83 (85)
48 (79)
82 (85)
703 (78)
12 (10)
4 (11)
7 (14)
9 (33)
9 (17)
10 (14)
17 (32)
8 (13)
3 (15)
10 (12)
3 (6)
10 (12)
102 (15)
90 (83)
28 (88)
27 (63)
7 (39)
38 (84)
53 (90)
33 (92)
44 (83)
13 (76)
58 (79)
25 (56)
60 (83)
476 (79)
9 (10)
3 (11)
1 (4)
1 (14)
5 (13)
8 (15)
7 (21)
4 (9)
2 (15)
8 (14)
3 (12)
7 (12)
58 (12)
* Excluding 49 subjects with missing information on pain status.
alence did not differ by occupational group (P ⫽ 0.751).
At 24 months, the new-onset rates ranged from 4% in
army officers to 21% in podiatrists, and the prevalence
did not differ according to occupational group (P ⫽
0.492). Furthermore, there was no difference in the
proportion of subjects reporting the new onset of wide-
spread pain by followup period for any occupational
group.
The new onset rate of widespread pain was 15%
and 12% at 12 and 24 months, respectively (Figure 1). At
12 months, the rate of new-onset widespread pain was
significantly higher in women (19%) than in men (12%)
Table 2. Work-related mechanical risk factors and new onset of widespread pain, univariate associations for manual handling
activities*
No. of subjects with new-onset widespread pain
12 months
Manual handling activity
Lifting with 1 hand
Never
ⱕ15 lbs
⬎15 lbs
Lifting with 2 hands
Never
ⱕ24 lbs
⬎24 lbs
Carrying on 1 shoulder
Never
ⱕ30 lbs
⬎30 lbs
Lifting weights at or above shoulder level
Never
ⱕ23 lbs
⬎23 lbs
Pushing
Never
ⱕ65 lbs
⬎65 lbs
Pulling
Never
ⱕ56 lbs
⬎56 lbs
24 months
Not exposed
Exposed
Not exposed
Exposed
OR
95% CI
296
137
161
42
31
25
192
116
104
24
18
16
1
1.7
1.9
Referent
1.1–2.7
1.1–3.3
270
165
153
43
30
27
202
105
104
30
12
16
1
1.3
1.7
Referent
0.8–2.1
1.0–2.8
482
53
58
76
11
14
330
44
37
47
5
6
1
1.1
1.6
Referent
0.6–2.0
0.9–3.0
448
63
80
71
16
14
324
47
39
43
9
6
1
2.0
1.7
Referent
1.2–3.3
0.9–3.2
393
92
106
69
18
14
284
70
57
36
11
11
1
1.5
1.7
Referent
0.9–2.5
0.96–3.0
448
65
80
72
13
16
321
51
36
42
7
9
1
1.6
2.3
Referent
0.9–2.9
1.3–3.9
* Adjusted for sex, age group, and occupation. OR ⫽ odds ratio; 95% CI ⫽ 95% confidence interval.
PREDICTORS OF NEW-ONSET PAIN IN NEWLY EMPLOYED WORKERS
1659
Table 3. Work-related mechanical risk factors and new onset of widespread pain, univariate associations for posture and repetitive movements*
No. of subjects with new-onset widespread pain
12 months
Posture and repetitive movements
Sitting
Do not sit as part of job
⬍2 hours
ⱖ2 hours to ⬍4 hours
ⱖ4 hours
Standing
Do not stand as part of job
⬍15 minutes
ⱖ15 minutes to ⬍2 hours
ⱖ2 hours
Driving as part of job
No
Yes
Kneeling
Never
⬍15 minutes
ⱖ15 minutes
Squatting
Never
⬍15 minutes
ⱖ15 minutes
Bending
Never
⬍15 minutes
ⱖ15 minutes
Stretching below knee level
Never
⬍15 minutes
ⱖ15 minutes
Working with hands at or above shoulder level
Never
⬍15 minutes
ⱖ15 minutes
Repetitive wrist movements
Never
⬍2 hours
ⱖ2 hours
Repetitive arm movements
Never
⬍2 hours
ⱖ2 hours
24 months
Not exposed
Exposed
Not exposed
Exposed
OR
95% CI
194
113
143
145
29
17
29
25
120
116
65
112
17
16
5
20
1
1.0
1.0
0.9
Referent
0.6–1.6
0.6–1.7
0.5–1.6
54
166
194
184
8
29
33
31
48
140
117
106
7
21
17
13
1
1.6
1.5
1.6
Referent
0.8–3.1
0.8–2.9
0.8–3.2
521
79
93
9
336
75
46
12
1
0.9
Referent
0.5–1.6
371
153
74
51
34
17
243
107
62
32
16
10
1
1.7
1.6
Referent
1.1–2.6
0.9–2.6
353
167
62
53
29
20
258
107
45
29
17
12
1
1.6
2.9
Referent
1.0–2.5
1.8–4.9
280
173
135
39
38
24
213
106
91
26
12
20
1.0
1.3
1.4
Referent
0.9–2.0
0.9–2.1
330
198
67
50
42
10
221
149
42
33
17
8
1
1.2
1.3
Referent
0.8–1.8
0.7–2.4
328
145
119
55
27
20
231
128
53
27
16
15
1
1.3
1.8
Referent
0.8–2.0
1.1–2.8
188
220
183
24
41
37
162
124
127
21
16
21
1
1.1
1.1
Referent
0.7–1.7
0.7–1.8
248
192
152
37
41
24
225
103
84
22
16
18
1
1.7
1.5
Referent
1.1–2.5
0.9–2.3
* Adjusted for sex, age group, and occupation. OR ⫽ odds ratio; 95% CI ⫽ 95% confidence interval.
(P ⫽ 0.012), although this difference did not persist at 24
months (11% prevalence in men compared with 14% in
women). Symptom onset was consistently higher among
women for all age groups, but this difference was not
statistically significant.
Univariate associations. Table 2 shows the univariate associations between mechanical exposures and
the new onset of widespread pain, adjusted for age, sex,
and occupation. Many of the manual handling activities
conferred an increased risk of symptom onset, including
lifting ⬎15 lbs with 1 hand (OR 1.9, 95% CI 1.1–3.3),
lifting ⬎24 lbs with 2 hands (OR 1.7, 95% CI 1.0–2.8),
and pulling heavy weights of ⬎56 lbs (OR 2.3, 95% CI
1.3–3.9). Of the postures and repetitive movements,
squatting for ⱖ15 minutes was the strongest predictor of
new-onset widespread pain (OR 2.9, 95% CI 1.8–4.9),
and those working with hands at or above shoulder level
for ⱖ15 minutes had an 80% increased odds of developing widespread pain at followup (Table 3).
Several work-related psychosocial factors showed
an increased risk of new-onset widespread pain (Table
4). A statistically significant association was found for
1660
HARKNESS ET AL
Table 4. Work-related psychosocial risk factors and new onset of widespread pain, univariate associations for job demand, job
satisfaction, social support, control over work, and individual distress*
No. of subjects with new-onset widespread pain
12 months
Psychosocial factor
Job demand
Stressful work
Never/occasionally
At least half of the time
Monotonous work
Never/occasionally
At least half of the time
Hectic work
Never/occasionally
At least half of the time
Job satisfaction
Satisfaction with job
Not dissatisfied
(Very)/dissatisfied
Social support
Support from colleagues
Not dissatisfied
(Very)/dissatisfied
Control over work
Control over own work
At least sometimes
(Very)/seldom
Learn new things
At least sometimes
(Very)/seldom
Individual distress, by GHQ
GHQ score
0
1–2
ⱖ3
24 months
Not exposed
Exposed
Not exposed
Exposed
OR
95% CI
480
113
67
34
346
66
50
8
1
1.5
Referent
0.99–2.3
531
61
80
21
359
51
47
11
1
2.4
Referent
1.5–3.9
417
173
62
39
309
103
42
16
1
1.4
Referent
0.97–2.1
580
12
96
5
392
18
54
4
1
2.1
Referent
0.9–4.6
584
7
98
3
399
12
54
4
1
2.4
Referent
0.96–6.0
531
60
90
9
394
17
52
6
1
1.4
Referent
0.8–2.5
570
24
95
6
390
22
55
3
1
1.7
Referent
0.7–4.1
348
163
90
45
28
27
271
77
69
37
12
8
1
1.2
1.5
Referent
0.8–1.9
0.97–2.4
* Adjusted for sex, age group, and occupation. OR ⫽ odds ratio; 95% CI ⫽ 95% confidence interval; GHQ ⫽ General Health
Questionnaire.
monotonous work (OR 2.4, 95% CI 1.5–3.9), and increased, although not statistically significant, associations were apparent for stressful work, hectic work, low
job satisfaction, and lack of support from colleagues. In
addition those with high levels of individual psychological distress, that is, those who scored ⱖ3 on the GHQ,
also had an increased risk of symptom onset (OR 1.5,
95% CI 0.97–2.4).
Of the work place environmental factors examined, those working in cold conditions had a lower risk of
symptom onset (OR 0.5, 95% CI 0.3–0.98) (Table 5).
Domain-specific models. Several exposures were
excluded from the domain-specific models because of
strong correlations with other variables. Lifting with 1
hand was correlated with lifting with 2 hands (r ⫽ 0.56),
and the latter was excluded from the manual handling
model, pushing was correlated with pulling (r ⫽ 0.50)
and was also excluded from the manual handling model.
Lifting weights at or above shoulder level was correlated
with working with hands at or above shoulder level (r ⫽
0.47), and the former was excluded from the manual
handling model. Kneeling was correlated with squatting
(r ⫽ 0.60) and was excluded from the posture model.
Therefore variables from the domain-specific
models that met our criteria for inclusion in the final
multivariate model were: lifting with 1 hand, pulling,
working with hands at or above shoulder level, squatting,
monotonous work, support from colleagues, hot working
conditions, and cold working conditions. In the environmental factors model, there was evidence of a protective
effect of cold working conditions. This is in contrast to
the findings of other investigators (16,17), and there is
no plausible hypothesized mechanism of action for such
a protective effect (18). Therefore, cold working conditions was excluded from the final multivariate model.
PREDICTORS OF NEW-ONSET PAIN IN NEWLY EMPLOYED WORKERS
1661
Table 5. Work place environment as risk factors for new onset of widespread pain, univariate associations*
No. of subjects with new-onset widespread pain
12 months
Environmental factor
24 months
Not exposed
Exposed
Not exposed
Exposed
OR
95% CI
452
147
70
31
309
101
44
12
1
1.5
Referent
0.9–2.2
473
107
83
15
340
69
53
3
1
0.5
Referent
0.3–0.98
435
116
80
13
314
94
47
10
1
0.6
Referent
0.4–1.1
Work in hot conditions
No
Yes
Work in cold conditions
No
Yes
Work in damp conditions
No
Yes
* Adjusted for sex, age group, and occupation. OR ⫽ odds ratio; 95% CI ⫽ 95% confidence interval.
Final multivariate model. In the final multivariate model (Table 6), those who pulled heavy weights had
an 80% increased, but not statistically significant, risk of
symptom onset compared with those who did not perform these activities. Those who squatted for ⱖ15
minutes and those who thought their work was monotonous or boring had a significantly increased (approximately double) odds of developing new-onset widespread pain. Those who reported low social support
from colleagues also had an increased risk of symptom
onset, but this association was not statistically significant. None of the interaction terms we assessed contributed significantly to the final model.
Using the factors with an odds ratio of ⱖ1.5 in
Table 6. Final model of the predictors of new-onset widespread
pain, multivariate associations*
Variable
Mechanical load
Pulling
Never
ⱕ56 kg
⬎56 kg
Squatting
Never
⬍15 minutes
ⱖ15 minutes
Psychosocial factors
Job demand
Monotonous work
Never/occasionally
At least half of the time
Social support
Support from colleagues
Not dissatisfied
(Very)/dissatisfied
Odds
ratio
95% confidence
interval
1
1.2
1.8
Referent
0.7–2.3
0.98–3.2
1
1.3
2.0
Referent
0.8–2.1
1.1–3.6
1
1.9
Referent
1.1–3.2
1
2.2
Referent
0.8–5.8
* Adjusted for sex, age group, occupation, and all other factors in the
model.
the final multivariate model, we were able to determine
the rate of new-onset widespread pain in subjects exposed to a combination of these factors. The new-onset
rate in any 12-month period increased from 11% (95%
CI 9.3–13.7) in those exposed to none of these factors to
60% (95% CI 26–88) in those exposed to ⱖ3 factors
(pulling ⬎56 lbs, squatting ⱖ15 minutes, monotonous
work, and low support from colleagues).
Respondents versus nonrespondents. Those who
responded to the questionnaire and those who did not
were found to differ on a number of potential risk
factors at 12 and 24 months (see Appendix B, available
on the Arthritis & Rheumatism Web site at http://
www.interscience.wiley.com/pages/0004-3591/suppmat/
index.html). However, due to the nature of the data
collection, we were able to further examine the relationship between baseline predictors and outcome at 12
months stratified by response status at 24 months. We
found no significant differences for the factors that were
included in the final multivariate model.
DISCUSSION
This is the first study conducted within an occupational setting to examine the relative effects of workrelated mechanical, psychosocial, and environmental
factors in relation to the new onset of widespread pain.
Widespread pain is common in this young, newly employed population, and the risk factors are multidimensional, with work-related mechanical factors and workrelated psychosocial factors playing an important role.
In interpreting these findings, there are a number
of methodologic considerations. The current study was
conducted among newly employed workers to minimize
the “healthy worker effect.” Individuals working in
1662
well-established work forces may be exposed to different
risk factors than those experienced by young, newly
employed workers. For example, in the current study,
relatively few subjects reported being exposed to adverse
work-related psychosocial factors. We did, however,
assess whether the healthy worker effect influenced the
present findings by investigating the proportion of subjects who changed their job at followup and determining
whether such job changes were due to aches or pains. A
total of 79 subjects left their baseline occupation during
followup, but only 1 of them reported any musculoskeletal symptoms. It therefore seems that the influence of
the healthy worker effect in the present study was
minimal. However, due to the nature of the jobs in the
current study, this cohort may have been healthier than
the general population, and some jobs required the
completion of rigorous fitness tests prior to employment.
Consequently, we may have underestimated the prevalence of new-onset widespread pain in relation to the
general population.
Due to the prospective design of the current
study, with exposure being measured a year prior to the
new onset of widespread pain, we were able to determine the temporal relationship between exposures and
outcomes. We made no attempt to ascertain widespread
pain status in the intervening months and are therefore
unable to say anything about the new-onset rate during
this time. However, this does not affect the internal
comparisons between predictors and outcomes. Misclassification of pain status at followup may have made it
more difficult to detect an effect. Changes in exposure
may also have occurred in the intervening months. The
suitable length of time over which to measure exposures,
particularly work-related psychosocial exposures, is
something that has recently been debated (19). We
assessed interactions between the followup period and
predictor variables to determine whether the relationship between exposures and outcomes had changed
during the followup period. We found that the relationship had not changed significantly for any of those
variables included in the final predictive model.
The outcome ascertained in this study was widespread pain, which was defined according to the ACR
guidelines used for the classification of fibromyalgia.
Estimates of chronic widespread pain in the general
population have been reported to be in the region of
10–13% (20–22), but we did not identify any studies
conducted within the work place. Previously, we found
that the majority of individuals who report widespread
body pain have experienced their pain for 3 months or
longer (20).
HARKNESS ET AL
The “new prevalence” rates observed in this
study of young, presumably healthy, workers was high.
Furthermore, a substantial proportion reported that
their pain had limited their normal activities, either at
work or at home (27% at 12 months and 31% at 24
months). Nevertheless, the proportion of these subjects
with chronic pain is likely to be smaller, and it is unlikely
(although not investigated) that more than a very small
proportion would be positive for the other features, such
as tender points, necessary to classify their condition as
fibromyalgia. In addition, the prevalence of widespread
pain at baseline was more common in men, whereas
chronic widespread pain and fibromyalgia tend to be
much more commonly reported in women. Thus, we
caution that the high prevalence rates we obtained
should not be taken as an indication of severe morbidity.
Despite this, it is thus of substantial interest that work
place psychological factors should show the positive
associations observed. It would be necessary to undertake longer-term followup of these subjects to determine
whether such factors have a similar, or even enhanced,
role in predicting the future development of disabling,
chronic widespread pain of the nature of fibromyalgia.
The work place exposures we analyzed may not
have been typical of a normal working day. However, in
an attempt to assess this and in response to a direct
question, we found that the majority of individuals
reported that the demands of the last working day were
much the same “as usual” (78% and 92% at 12 and 24
months, respectively). Importantly, the proportion of
subjects reporting demands as being less physically demanding or more physically demanding during the last
working day did not differ according to pain status at
followup.
We have found within this population, as with
other study populations, that monotonous work is one
factor that consistently predicts new-onset musculoskeletal pain (10,23). Although monotonous work could be a
marker of repetitive tasks, such as movements of the
arms or wrists, it was found to be independently predictive. Monotonous work may lead to increased psychological job stress, which might explain adverse health
outcomes, including the onset of musculoskeletal pain
(18). Another possible explanation is that subjects who
perceive their work as monotonous or boring have a
lower pain threshold than those who do not perceive
their work in the same way. Other investigators observed
a trend toward an increasing prevalence of fibromyalgia
in association with increasing levels of physical work
stress, but not mental stress (5). However, that study was
cross-sectional, which makes it difficult to establish the
PREDICTORS OF NEW-ONSET PAIN IN NEWLY EMPLOYED WORKERS
temporal relationship and introduces the possibility of
recall bias. It also was not clear how levels of physical
and mental stress were measured.
More recently, we examined the relationship
between work place factors and the new onset of chronic
widespread pain among an unselected population sample (6). As in the current study, the risk of the new onset
of chronic widespread pain was found to be multifactorial, with the strongest associations for repetitive movements of the wrists, other regional pain symptoms, and
individual psychosocial factors, in particular, illness behavior. However, that study was conducted among a
stable work force, with the majority of subjects (95%)
being in the same employment for the previous 36
months. In addition, job histories were collected retrospectively and may have been influenced by recall bias.
Furthermore, that study did not include as extensive
measurements of work-related risk factors as those
collected in the current study. In that study, however, as
in the current study, we did not measure major physical
trauma (e.g., work place accidents), which have been
implicated in the onset of widespread pain syndromes
(3,4). Our conclusions are restricted to low-grade workrelated trauma.
The current study has potential implications for
interventions designed to prevent the new onset of
widespread musculoskeletal pain in the work place. Such
studies are currently limited. One small study of fibromyalgia patients (n ⫽ 86) found no difference in the job
difficulty subscale of the Fibromyalgia Impact Questionnaire in 3 groups of subjects (control, education, and
education plus physical therapy) (24). Further research
is required to investigate the effectiveness of workrelated psychosocial interventions, for example, reducing the perception of monotonous work may be achieved
through more-frequent job rotation or more-varied work
tasks, whereas increased social support may be achieved
through more contact with line managers or availability
and accessibility to occupational health professionals.
In summary, this study is the first to examine the
relationship between work-related mechanical, psychosocial, and environmental factors and the new onset of
widespread pain in a cohort of newly employed workers.
We demonstrated that the new onset of widespread pain
is common and the risk is multifactorial. The strongest
independent predictors of symptom onset were, however, work-related psychosocial factors, and these associations have implications for the development of possible interventions.
1663
ACKNOWLEDGMENTS
We would like to thank the individuals who permitted
us access to their work forces and to all the workers who
participated in the study. We would also like to thank Professor Nicola Cherry, who was involved in aspects of study design
and conduct, and Christina Pritchard and Stewart Taylor, who
were involved in the data collection.
REFERENCES
1. McBeth J, Macfarlane GJ, Benjamin S, Silman AJ. Features of
somatization predict the onset of chronic widespread pain: results
of a large population-based study. Arthritis Rheum 2001;44:940–6.
2. Greenfield S, Fitzcharles MA, Esdaile JM. Reactive fibromyalgia
syndrome. Arthritis Rheum 1992;35:678–81.
3. Al Allaf AW, Dunbar KL, Hallum NS, Nosratzadeh B, Templeton
KD, Pullar T. A case-control study examining the role of physical
trauma in the onset of fibromyalgia syndrome. Rheumatology
(Oxford) 2002;41:450–3.
4. Buskila D, Neumann L, Vaisberg G, Alkalay D, Wolfe F. Increased rates of fibromyalgia following cervical spine injury: a
controlled study of 161 cases of traumatic injury. Arthritis Rheum
1997;40:446–52.
5. Makela M, Heliovaara M. Prevalence of primary fibromyalgia in
the Finnish population. BMJ 1991;303:216–9.
6. McBeth J, Harkness EF, Silman AJ, Macfarlane GJ. The role of
workplace low-level mechanical trauma, posture and environment
in the onset of chronic widespread pain. Rheumatology (Oxford)
2003;42:1486–94.
7. Nahit ES, Macfarlane GJ, Pritchard CM, Cherry NM, Silman AJ.
Short term influence of mechanical factors on regional musculoskeletal pain: a study of new workers from 12 occupational groups.
Occup Environ Med 2001;58:374–81.
8. Pope DP, Silman AJ, Cherry NM, Pritchard C, Macfarlane GJ.
Validity of a self-completed questionnaire measuring the physical
demands of work. Scand J Work Environ Health 1998;24:376–85.
9. Karasek RA. Job demands, job decision latitude and mental strain:
implications for job redesign. Adm Sci Q 1979;24:285–311.
10. Macfarlane GJ, Hunt IM, Silman AJ. Role of mechanical and
psychosocial factors in the onset of forearm pain: prospective
population based study. BMJ 2000;321:676–9.
11. Leino PI, Hanninen V. Psychosocial factors at work in relation to
back and limb disorders. Scand J Work Environ Health 1995;21:
134–42.
12. Karasek RA, Theorell T. Healthy work: stress, productivity and
reconstruction of working life. New York: Basic Books, 1990.
13. Goldberg DP, Williams P. Users’ guide to the General Health
Questionnaire. Windsor (UK): NFER-Nelson; 1988.
14. Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C,
Goldenberg DL, et al. The American College of Rheumatology
1990 criteria for the classification of fibromyalgia: report of the
multicenter criteria committee. Arthritis Rheum 1990;33:160–72.
15. Liang KY, Zeger SL. Longitudinal data analysis using generalised
linear models. Biometrika 1986;73:13–22.
16. Jin K, Sorock GS, Courtney T, Liang Y, Yao Z, Matz S, et al. Risk
factors for work-related low back pain in the People’s Republic of
China. Int J Occup Environ Health 2000;6:26–33.
17. Pienimaki T. Cold exposure and musculoskeletal disorders and
diseases: a review. Int J Circumpolar Health 2002;61:173–82.
18. Zakaria D, Robertson J, MacDermid J, Hartford K, Koval J.
Work-related cumulative trauma disorders of the upper extremity:
navigating the epidemiologic literature. Am J Ind Med 2002;42:
258–69.
19. Hoogendoorn WE, Bongers PM, de Vet HC, Twisk JW, van
1664
Mechelen W, Bouter LM. Comparison of two different approaches for the analysis of data from a prospective cohort study:
an application to work related risk factors for low back pain.
Occup Environ Med 2002;59:459–65.
20. Croft P, Rigby AS, Boswell R, Schollum J, Silman A. The
prevalence of chronic widespread pain in the general population.
J Rheumatol 1993;20:710–3.
21. Hunt IM, Silman AJ, Benjamin S, McBeth J, Macfarlane GJ. The
prevalence and associated features of chronic widespread pain in
the community using the ‘Manchester’ definition of chronic widespread pain. Rheumatology (Oxford) 1999;38:275–9.
HARKNESS ET AL
22. Buskila D, Abramov G, Biton A, Neumann L. The prevalence of pain
complaints in a general population in Israel and its implications for
utilization of health services. J Rheumatol 2000;27:1521–5.
23. Harkness EF, Macfarlane GJ, Nahit ES, Silman AJ, McBeth J.
Mechanical and psychosocial factors predict new onset shoulder
pain: a prospective cohort study of newly employed workers.
Occup Environ Med 2003;60:850–7.
24. Burckhardt CS, Mannerkorpi K, Hedenberg L, Bjelle A. A
randomized, controlled clinical trial of education and physical
training for women with fibromyalgia. J Rheumatol 1994;21:
714–20.
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