Occupational Medicine Advance Access originally published online on June 16, 2006
Occupational Medicine 2006 56(6):406-413; doi:10.1093/occmed/kql040
© The Author 2006. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Incidence and suspected cause of work-related musculoskeletal disorders, United Kingdom, 1996–2001
Yiqun Chen1,
J. Corbett McDonald2 and
Nicola M. Cherry3
1 Centre for Occupational and Environmental Health, University of Manchester, Manchester, UK
2 Occupational and Environmental Medicine, Imperial College School of Medicine, London, UK
3 Department of Public Health Sciences, University of Alberta, Edmonton, Canada
Correspondence to: Yiqun Chen, Surveillance Group, Division of Population Health and Information, Alberta Cancer Board, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta, Canada T6G 1Z2. Tel: +1 780 432 8347; fax: +1 780 432 8645; e-mail: yiqunche{at}cancerboard.ab.ca
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Abstract
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Background Musculoskeletal conditions are the most common self-reported
work-related disease, with high costs incurred from long-term
disability. In the United Kingdom, occupational physicians and
rheumatologists have been reporting new cases of work-related
musculoskeletal disorders to voluntary surveillance schemes
since 1996.
Aims To estimate population incidence rates for work-related musculoskeletal disorders reported by rheumatologists and occupational physicians by occupation and industry, in relation to tasks and movements suspected as causal.
Methods Estimated average annual incidence rates were calculated for nine main job categories and eight industrial groups; Labour Force Survey figures were used as the denominator for rheumatologists, and a special survey for the occupational physicians. These were then related to tasks and movements reported as causal.
Results Between October 1997 and the end of 2001, an estimated 2599 new cases/year were reported by rheumatologists, and from January 1996, 5278 cases/year by occupational physicians. Average annual rates overall were 94 per million for rheumatologists and 1643 per million for occupational physicians (a 17-fold difference). Jobs at highest risk for the upper limb were primarily clerical, craft-related and machine work. Tasks associated with upper limb disorders and with neck and back problems were predominantly keyboard work and heavy lifting, and in craft-related occupations with gripping or holding tools.
Conclusions Jobs at risk and the associate tasks were identified which should assist prevention, but the extent to which these factors were causal or aggravating previous injury requires further study. The much higher rates reported by occupational physicians reflect, in part, the type of industries they served.
Keywords Back; lower limb; musculoskeletal; surveillance; upper limb; work-related
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Introduction
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A clinically based voluntary reporting scheme for occupational
disease was started in the United Kingdom in 1989, first for
respiratory illnesses [
1], and then in turn for dermatoses [
2],
infectious disease [
3], audiological disorders [
4], musculoskeletal
problems [
5], and mental ill-health [
6]. These six schemes,
together with one for occupational physicians for all types
of work-related illness [
7], were brought together under the
umbrella of Occupational Disease Intelligence Network (ODIN)
in 1998, coordinated from the Centre for Occupational and Environmental
Health at the University of Manchester. Numerous reports have
been published on these schemes over the years but, when ODIN
was superseded by The Health and Occupation Reporting network
in 2002, it was considered useful to summarize the main information
provided by ODIN; this paper has this objective for the musculoskeletal
group. An initial report published in 2001 [
5] described the
evolution and methods of the scheme, which became known as Musculoskeletal
Occupational Surveillance Scheme (MOSS), launched in late 1997,
with the full support of the British Society of Rheumatology.
That report dealt only with some 8000 new cases reported by
rheumatologists in the first 3 years of the scheme, and excluded
cases reported by occupational physicians. Of the total, two-thirds
related to injury to the upper limb, the remainder about equally
to the lumbar spine, shoulder and cervical spine. The current
analysis will cover all cases reported 1997–2001 by rheumatologists
and 1996–2001 by occupational physicians, and will in
particular examine incidence rates by occupation and industry.
It will also examine the association between disorders reported
by rheumatologists and those physical risk factors (tasks and
movements) thought to have been responsible [
8].
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Methods
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Some 330 participating consultant rheumatologists (
80% of the
Society's membership) were enrolled in MOSS in 1997. Initially,
these physicians were allocated at random to one of 3 months,
October–December 1997. From January 1998, the scheme continued
with rheumatologists randomly allocated to 1 month during each
year and asked to report all new cases of work-related musculoskeletal
disorders seen during the assigned month [
5]. Occupational physicians
began systematically to report all kinds of work-related ill-health,
including work-related musculoskeletal disorders in 1996. Initially
800 occupational physicians agreed to take part in the surveillance
scheme (the Occupational Physicians Reporting Activity—OPRA).
This amounted to
75% of occupational physicians who were in
active practice in the United Kingdom and who were on the Specialist
Register [
7]. Between 1996 and 2001, participating occupational
physicians had been reporting for one randomly allocated month
in each calendar year. The estimated number of cases that would
have been reported within each 12 months was calculated by multiplying
the number of cases per month by 12 (or by 3 for MOSS reporters
in 1997). The estimated annual average numbers have been used
throughout this analysis. Cases reported to OPRA by Health &
Safety Executive medical inspectors were excluded. In both schemes,
physicians were asked to report cases that they considered caused
or made substantially worse by work. A pre-existing disease
in which work exposure made a substantial difference in severity
could also be included. The decision on work-relatedness was
based essentially on whether the disease would have occurred
in the absence of occupational factors.
The reported occupation is coded to three digits and industry to two digits using the Standard Occupational Classification and the Standard Industrial Classification schemes developed by the Office of Population Censuses and Surveys and the Central Statistical Office (now jointly the Office for National Statistics) [9,10]. Denominators for the reports from rheumatologists were obtained from the Labour Force Survey [11], which estimates UK employment figures for occupation and industry by age, sex and region. Employment data from 1999 were used in calculating the rates presented here. For the purpose of this report, distributions by occupation are presented in nine main job categories and by industry in the eight main groups used in analyses of cases reported by occupational physicians [12]. However, as only about 12% of the working population were served by the participating occupational physicians, results of a special survey conducted in 2001 were used as the denominator for the latter [13].
Coding of risk factor
Between October 1997 and December 1999, 667 new cases of musculoskeletal disease were reported by >300 consultant rheumatologists in the United Kingdom, together with a short description of the tasks and activities they considered to have been causal [8]. Almost all these descriptions were related to exposures of physical risk factors. By summarizing physicians' descriptions, a coding scheme of physical risk factors was developed comprising 16 categories of task codes and another 16 categories of movement codes. The reliability of this scheme has been discussed elsewhere [8] but briefly, four reviewers coded the work activities independently for 576 cases, in which a specific diagnosis had been attributed to repeated exposure. The fourth rater coded the cases twice. With the use of a single summary kappa statistic and a matrix of kappa coefficients [14], both inter-rater reliability and intra-rater reliability were assessed. The overall inter-rater agreement on the task (
= 0.73) and movement ( = 0.79) was good. The intra-rater agreement was somewhat better than the inter-rater agreement on both dimensions. The results suggest that the coding scheme was, on the whole, reliable for classifying the physical risk factors reported, and coding of rheumatologists reports was continued to December 2001.
Confidence intervals
Exact 95% confidence intervals (CIs) were calculated for incidence rates taking into account the number of reported cases (numerator) and the number of employed persons in the denominator. The number of reported cases was assumed to be Poisson distributed.
Ethical approval was considered not to be required as physician reports were anonymous. This position had later been confirmed by the North West Multi-centre Research Ethics Committee for the continuation of the data collection.
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Results
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The estimated annual number of cases reported by rheumatologists
and occupational physicians, together with rates per million
employees at risk, are shown in
Table 1. The overall rates,
based on occupational physician reports (annual average rate/million
= 1643, 95% CI: 1599–1688), were much higher than those
reported by rheumatologists (94, 95% CI: 91–98). The latter
rate was higher for women (104, 95% CI: 99–110) than for
men (84, 95% CI: 79–88), particularly for hand/wrist/arm.
The opposite can be seen for cases reported by occupational
physicians where men had higher overall rates (1745, 95% CI:
1681–1810) than women (1530, 95% CI: 1469–1592),
with a higher rate at all sites except shoulder and neck/thoracic
spine and with a nearly three times higher rate of hip/knee
disorders.
In
Table 2, the same data were analysed in more detail by anatomical
site. As noted previously [
5], the upper limb was most often
affected, followed by neck or back; there were relatively few
cases of the lower limb. For cases reported by occupational
physicians, a frequent problem was pain of ill-defined pathology,
particularly at the hand, wrist, arm or shoulder.
The distribution of average annual rates is examined in
Table 3 in nine main categories of occupation at the three main anatomical
sites. Similar analyses in eight broad categories of industry
are presented in
Table 4. Again the rates were all much higher
when based on reports from occupational physicians than rheumatologists.
Overall, however, it is evident from
Table 3 that the jobs at
highest risk were similar, whether reported by rheumatologists
or by occupational physicians. For upper limb, these were primarily
clerical, craft-related and machine work. Within the craft-related
category, builders, decorators, fitters, welders and textile
machinists were frequently mentioned (data not shown). For neck
and back disorders, craft-related and machine work were again
prominent, though workers in personal and protective services
were also at high risk, together with associated professional
workers (mainly nursing staff) in reports of occupational physicians.
Craft-related and machine workers were also at risk for lower
limb disorders. The overall rates for any musculoskeletal disorder
were highest for craft-related workers in each of the schemes
(MOSS 173, 95% CI: 159–189; OPRA 4513, 95% CI: 4206–4837).
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Table 3. Estimated average annual cases and incidence rates per million by anatomical region and major occupational groups
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Table 4. Estimated average annual cases and incidence rates per million by anatomical region and major industrial groups
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Industries at high risk (
Table 4) were also fairly similar,
with disorders at all three anatomical sites being increased
in mining and in food and organic product manufacture, and of
the upper and lower limbs in utilities and construction. The
overall rates for any musculoskeletal disorder were highest
for mining and quarrying in both schemes (MOSS 604, 95% CI:
458–775; OPRA 9375, 95% CI: 7876–11077). Frequently
reported conditions in mining included hand–arm vibration
syndrome (HAVS), mechanical back pain and disorders of hip and
knee (data not shown). Employees in metallic and automotive
products manufacturing were also at high risk for upper limb
disorders. Production workers in car manufacturing, aircraft
fitters and welders in shipbuilding were frequently reported
jobs of this group. Among reports for those in ‘other
industries’, the highest numbers were for workers in public
administration and defence and the retail trade in both MOSS
and OPRA but in MOSS, where risks for these subgroups could
be calculated, the risks/million were below the mean for all
sites except for neck/back disorders (38) in public administration
and defence.
Information reported by rheumatologists on factors they considered causal is shown for each anatomical region by task in Table 5, and movement in Table 6. Tasks associated with upper limb disorders were predominantly ‘keyboard work’, ‘guiding/holding building tools’ and, to a lesser extent, ‘heavy lifting’; those associated with neck and back disorders were predominantly heavy lifting but also keyboard work. For lower limb problems, coordinated whole body movement was most frequently reported, but also heavy lifting. The associated movements (Table 6) show that upper limb disorders were overwhelmingly associated with ‘fine hand work’ and ‘forceful grip’, neck/back with ‘lifting’ and lower limb with ‘standing and walking’.
The tasks and movements suspected to be causal were studied
by occupation and industry. The disorders associated with craft-related
occupations were most frequently attributed to guiding or holding
tools (tasks) and forceful upper limb grip (movements), whereas
the problems experienced by clerical workers were predominantly
related to keyboard work (tasks) and fine handwork (movement).
Many disorders in personal and protective services, where, for
example, care assistants were often reported, were attributed
to lifting tasks. Heavy lifting/carrying is a potential hazard
in most industries, and the guiding or holding of tools in many.
Forceful upper limb work was implicated in most industries but
few other movements, except fine handwork and lifting, were
mentioned frequently.
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Discussion
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The results presented in this paper raise two main questions,
the first on the very large difference between rates based on
the two groups of reporting physicians and the second on the
causal interpretation of the analyses of tasks and movements.
The close correlation between the pattern of illness from the
two sets of rates—although one is some 17 times higher
than the other—suggests that both groups of reporters
were observing essentially the same types of work-related disease,
but that rheumatologists were seeing only the tip of the iceberg.
This may well be so, as most musculoskeletal problems do not
require referral to a hospital specialist; a worker may simply
be treated by a general practitioner. It may also be that, in
companies with an occupational physician, early detection and
management obviate the need for specialist referral. These hypotheses
could be tested to see whether there is any difference in outcome
from the various referral routes. Since only about 12% of employees
are served by an occupational physician, a comparison of outcomes
in those with and without this resource might help to elucidate
the question.
Correct interpretation of both incidence and reported cause of work-related musculoskeletal disorders is clearly affected by the inconsistencies or potential bias in the reporting procedure. Cases reported by rheumatologists and even by occupational physicians can only capture a small proportion of the more severe cases in the working population from which they draw their patients, a proportion that may vary from industry to industry: the high rates of occupational disease reported from the mining industry, for example, probably reflect both the rapidly shrinking denominator and the high coverage of work-related illness by the occupational health services. In other industries, particularly those without occupational health provision, many employees with musculoskeletal conditions may not seek medical care; or if seen by a general practitioner, not be referred to a rheumatologist, only 70–80% of whom participate in MOSS. Even so, this should not seriously affect a comparison of risks between industries and occupations, providing that appropriate denominators are used.
Although there have been a number of studies of factors associated with musculoskeletal pain within industry [15–17], no similar analyses have been made, so far as we are aware, of the suspected role of tasks and movements in the causation of new cases of musculoskeletal disorders in the general working population. Psychosocial risk factors, although their roles in the aetiology are still inconclusive, may also contribute to the development of work-related musculoskeletal disorders [18]. As almost all cases reported by physicians were related to physical risk factors and only in very few cases psychosocial factors were also mentioned, this analysis of causes was limited to physical risk factors. The extent to which the factors reported caused the disorder, exacerbated an existing condition or reflected changes in work methods resulting from the disability might well be different if based on reports from rheumatologists or physicians in occupational health. Thus, it is clear that we need comparable data on tasks and movements from the occupational physicians, as their cases would probably have been much closer to the causal event. Taking the analyses in Tables 5–8 at face value, however, we are left with the question of the extent to which the opinion of the reporting physician was largely that of the patient (please note that Tables 7 and 8 are available as Supplementary data at Occupational Medicine Online).
Two recent studies [19,20] of physicians' beliefs and habits in reporting musculoskeletal disorders suggest that they are generally cautious in attributing these to occupational factors. This may lead to underestimation of disease incidence; nevertheless, the findings on task and movement are in line with those from cross-sectional and prospective studies carried out in industry [15–17] and suggest that heavy lifting and the forceful use of hand tools should continue to be priorities for prevention.
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Conflicts of interest
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None declared.
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Acknowledgements
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We are grateful to the Health & Safety Executive (United
Kingdom) for providing funding for the ODIN reporting schemes,
to the professional bodies (the British Society for Rheumatology
and Society of Occupational Medicine) whose support made the
schemes possible and to the reporting physicians.
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Abstract
Introduction