PREVALENCE AND CORRELATES OF REGIONAL PAIN AND ASSOCIATED
DISABILITY IN JAPANESE WORKERS
Keith T Palmer2
1Clinical Research Centre for Occupational Musculoskeletal Disorders, Kanto Rosai
Hospital, Kawasaki, Japan.
2MRC Epidemiology Resource Centre, University of Southampton, Southampton, UK
3Community Clinical Sciences, School of Medicine, University of Southampton,
4Department of Nursing, University of Tokyo Hospital, Tokyo, Japan
5Department of Joint Disease Research, University of Tokyo, Tokyo, Japan
Professor David Coggon
MRC Epidemiology Resource Centre
Southampton General Hospital
Southampton SO16 6YD
Tel: #44 2380 777624
Fax: #44 2380 704021
Key words: Musculoskeletal, pain, disability, sickness absence, somatising
Running title: Regional pain in Japanese workers
Word Count: 2952
To assess the prevalence and correlates of regional pain and associated disability in four
groups of Japanese workers.
As part of a large international survey of musculoskeletal symptoms (the CUPID study),
samples of nurses, office workers, sales/marketing personnel and transportation operatives
in Japan completed a self-administered questionnaire (response rate 83%). The
questionnaire covered experience of pain in six anatomical regions, associated disability and
sickness absence, and various possible occupational and psychosocial risk factors for these
outcomes. Associations with risk factors were assessed by logistic regression.
Analysis was based on 2290 subjects. Rates of regional pain were generally less than have
been reported in the UK, with a particularly low prevalence of wrist/hand pain among office
workers (6% in the past month). The strongest and most consistent risk factor for regional
pain in the past month was tendency to somatise (odds ratios (95% confidence intervals) for
report of ≥2 v 0 distressing somatic symptoms 3.1 (2.4-4.0) for low back pain, 2.8 (2.1-3.8)
for shoulder pain, and 2.5 (1.6-4.1) for wrist/hand pain). Sickness absence for regional pain
complaints in the past year was reported by 5% of participants, the major risk factor for this
outcome being absence during the same period for other medical reasons (OR 3.7, 95%CI
Japanese office workers have markedly lower rates of wrist/hand pain than their UK
counterparts. In Japan, as in Western Europe, somatising tendency is a major risk factor for
regional pain. Sickness absence attributed to regional pain complaints appears to be much
less common in Japan than in the UK, and to be driven principally by a general propensity to
take sickness absence.
Japanese office workers have markedly lower rates of wrist/hand pain than office
workers in the UK.
In Japan, as in Western Europe, somatising tendency is a major risk factor for
Sickness absence attributed to musculoskeletal disorders appears to be much less
common in Japan than in the UK.
What this paper adds
Our findings add weight to a growing body of evidence that the occurrence of
musculoskeletal symptoms and of resultant disability and sickness absence varies markedly
between countries. Strategies to control work-related musculoskeletal disorders should take
into account the factors that underlie these differences, which may include culturally
determined health beliefs and expectations.
Musculoskeletal pain, especially in the back, neck and upper limb, is a common complaint in
many developed countries, and an important cause of disability and incapacity for work. It is
often attributed to strain from forceful or repetitive occupational activities, and
epidemiological research has demonstrated fairly consistent associations of low back pain
with work involving heavy lifting and/or repeated bending of the trunk , and of painful
disorders of the forearm with work that entails repetitive movements of the wrist or hand .
However, regional pain complaints and associated disabilities are not a simple consequence
of physical stresses to tissues. There is strong evidence that they are influenced also by
psychological factors such as low mood and a general tendency to worry about common
somatic symptoms (somatising tendency) [3,4]. In addition, culturally determined health
beliefs could also have an important role, and may explain large variations in the incidence
and prevalence of pain and disability that have been observed between countries [5,6], and
within countries over time . It is important to understand the contribution of these
psychosocial influences if preventive measures are to be optimised.
To help advance knowledge in this area, a multi-centre international study, CUPID (Cultural
and Psychosocial Influences on Disability), has been established. The study, which is being
carried out in 19 countries (both developing and developed) from six continents, involves a
baseline cross-sectional survey that will allow comparison of rates of regional pain and
associated disability in samples of workers who carry out similar physical activities, but in
widely different cultural environments. This is followed by a longitudinal component, which
explores predictors of persistent and newly incident pain.
In this paper, we report findings from the initial cross-sectional survey that was carried out in
Japan as part of the CUPID study, and draw comparisons with experience in the UK.
The survey focused on four occupational groups – nurses, office workers, sales/marketing
personnel and transportation operatives. All participants worked in or near to Tokyo. The
nurses were employed at Tokyo University Hospital; the office workers in administrative and
clerical jobs at the same hospital and at a four pharmaceutical companies and a private
trading company, the sales/marketing personnel at six pharmaceutical companies, and the
transportation operatives (mainly lorry drivers and loaders) at two companies transporting
baggage and mail.
Within each participating organisation, a manager agreed to act as a coordinator for data
collection. The coordinator distributed a self-administered questionnaire to all employees in
relevant jobs, with a covering letter from the survey team. Completed questionnaires were
then returned to the survey team via the coordinator. A total of 3187 questionnaires were
distributed to 1074 nurses, 425 office workers, 380 sales/marketing personnel and 1308
transportation operatives. No reminders were sent to non-responders.
The questionnaire was a Japanese translation of the survey instrument that is being used
throughout the CUPID study. The accuracy of the translation was checked by independent
back-translation to English and comparison with the original. Amendments were then made
as necessary. Among other things, the questionnaire asked about demographic
characteristics, hours of work and duration of employment in current job, whether the job
involved certain specified activities in an average working day, job satisfaction, mental
health, indicators of tendency to somatise, experience of pain during the past month and
past year at each of six anatomical sites (low back, neck, shoulder, elbow, wrist/hand and
knee), disability for specified everyday tasks arising from such pain, and absence from work
in the past year because of musculoskeletal pain or for other reasons. Mental health (mood)
was assessed from the relevant subscale from the SF-36 questionnaire , and was graded
to three levels defined by approximate thirds of the distribution of scores in all subjects
combined. Somatising tendency was assessed using a subset of items from the Brief
Symptom Inventory (BSI) , and was graded according to the number of symptoms (out of
a total of seven) that were reported as causing at least moderate concern in the past week.
Data from the completed questionnaires were entered onto computer, and after checks for
errors, were analysed using SPSS Version 15 and STATA Version 10 software. Because a
major focus of the study was pain and disability during the past year, subjects were excluded
from the main analysis if they had worked in their current job for less than a year.
In addition to the compilation of simple descriptive statistics, logistic regression was used to
explore associations with regional pain (classified in various ways) and associated disability
and sickness absence. Pain at an anatomical site was considered disabling if during the
past month, it had made at least one of the everyday activities specified in the questionnaire
difficult or impossible. These activities were: getting dressed (all sites of pain), doing normal
household jobs (all sites of pain), cutting toe nails (low back), combing or brushing hair
(shoulder), bathing/showering (shoulder), opening bottles, jars or taps (elbow and
wrist/hand), writing (wrist/hand), locking and unlocking doors (wrist/hand), walking up and
down stairs (knee) and walking on level ground (knee). When looking at associations with
occupational activities, we defined for each site of pain, an activity in an average working
day that could cause physical stress to local tissues. These activities were: lifting weights of
≥25 kg by hand (low back); work with the hands above shoulder height for ≥1 hour in total
(neck and shoulders); repeated bending and straightening of the elbow for ≥1 hour in total
(elbow); use of a keyboard or other repetitive movements of the wrist/fingers for ≥4 hours in
total (wrist/hand); and kneeling or squatting for ≥1 hour in total (knees). Associations in the
logistic regression analyses were summarised by odds ratios (ORs) with associated 95%
confidence intervals (CIs).
Ethical approval for the study was provided by the University of Tokyo Ethics Committee.
Questionnaires were returned by 2651 (83%) of the workers to whom they were issued, but
285 were excluded from analysis because the individual had been in his/her current job for
less than a year, and a further 76 because of missing information on age (52), sex (1) or
both (23). Of the remaining 2290 subjects, 599 were nurses, 316 were office workers, 355
were sales/marketing personnel, and 1020 were transportation operatives, representing
56%, 74%, 93% and 78% of those mailed in the respective occupational groups..
Table 1 summarises various characteristics of the participants. Most of the nurses were
women, whereas almost all of the sales/marketing personnel and transportation operatives
were men. The majority of subjects were employed full-time, including 30% of the sample
(mostly sales/marketing personnel and transportation operatives) who indicated that they
worked for more than 60 hours per week. Reported occupational activities were much as
would be expected, with a high frequency of keyboard use by office workers (89%).
Transportation operatives and nurses had the highest prevalence of heavy lifting (83% and
66% respectively) and of repeated bending and straightening of the elbow (78% and 72%).
Rates of job satisfaction were relatively low in office workers (28%) and sales/marketing
personnel (31%). Poor mental health and tendency to somatise were most common among
the nurses. In the study sample overall, the somatic symptoms most frequently reported as
distressing were nausea or upset stomach (14%), weakness (12%) and faintness or
Table 2 shows the prevalence of pain at different anatomical sites in the study sample as a
whole. The lower back was the site most commonly affected by pain, with a prevalence of
28% in the past month. Next most common were pain in the neck (21% in the past month)
and shoulder (17%). In comparison, pain in the elbow and wrist/hand was much less
frequent. The sites most commonly affected by disabling pain in the past month were the
lower back (11%) and knee (8%). Only 4% of subjects had been absent from work during the
past year because of low back pain, and absence because of pain in the elbow or wrist/hand
was extremely rare.
The prevalence of regional pain by occupational group is summarised in Table 3 (data for
men and women separately are given in Supplementary Tables 1 and 2). At almost all
anatomical sites, pain in the past month was most common in nurses or transportation
operatives, and least frequent in sales/marketing personnel. However, office workers had
the highest prevalence of sickness absence in the past year attributed to regional pain
(11%). A total of 251 subjects (11%) reported pain in the past month at ≥3 anatomical sites,
744 (32%) reported disabling pain at one or more sites during the past month, and 125 (5%)
indicated that they had taken sickness absence during the past year because of regional
Table 4 gives results from logistic regression analyses exploring risk factors for pain at
different anatomical sites. For each site, two outcomes were examined – any pain in the
past month and disabling pain in the past month – the comparator in both cases being no
pain at the site in the past month. All analyses were adjusted for sex, age, mental health
and occupational group. Significant associations with locally stressful physical activities
were observed for pain in the low back (lifting ≥25 Kg), wrist/hand (use of use of keyboard or
repeated movements of a hands/fingers for ≥4 hours) and knee (kneeling or squatting for ≥1
hour). However, the strongest and most consistent associations were with somatising
tendency. For disabling pain in the low back, neck and shoulder, the ORs for report of ≥2 v
0 distressing somatic symptoms were all 4.5 or higher. Associations with poor mental health
(not shown) were much weaker than those with somatising tendency, and not statistically
Table 5 presents findings from two regression analyses, one for the risk of pain in the past
month at ≥3 anatomical sites, and the other for disabling pain at one or more anatomical
sites in the past month. In each case, the comparator was no pain at any site in the past
month. Both variables were strongly associated with somatising tendency and showed a
clear, progressive increase in risk in relation to the number of stressful physical activities
reported. In addition, both were more frequent at older ages. Associations with poor mental
health and job dissatisfaction were much weaker.
In contrast, sickness absence because of regional pain in the past year was unrelated to
occupational physical activities and showed no clear association with somatising tendency
(Table 6). It was, however, strongly associated with sickness absence during the past year
for other reasons (OR 3.7, 95%CI 2.4-5.8), which was reported by 16% of participants.
In this cross-sectional survey of Japanese workers, rates of regional pain were generally
lower than have been reported in the UK, with a particularly low frequency of pain in the wrist
and hand. The prevalence of sickness absence attributed to regional pain was also
substantially lower than in the UK. Pain at most sites was more common in workers who
indicated that they were exposed to stressful physical activities in their job, but the strongest
and most consistent risk factor for regional pain and associated disability was somatising
tendency. In contrast, risk of sickness absence because of regional pain was related not to
physical activities or somatising tendency, but to absence from work because of other health
The occupational groups that were studied cannot necessarily be regarded as representative
of the general population of working age in Japan. Nevertheless, they encompass a range
of occupational tasks, both manual and non-manual, and provide useful insights into
patterns of musculoskeletal symptoms and disability in a cultural environment that is notably
different from that in, say, Western Europe. Furthermore, the high response rate that was
achieved makes it likely that the samples of workers who participated were fairly typical of
the occupational groups from which they were drawn.
A concern always in international studies of this type is that the meaning of questions may
be distorted in translation between languages. Thus, care was taken to check the accuracy
of the Japanese questionnaire by back-translation to English. It remains possible that a term
such as “pain” is understood somewhat differently in Japan. However, this should not affect
the relative frequency of the symptom at different anatomical sites, and is less likely to have
been a problem in relation to more objective outcomes such as sickness absence.
Another possible source of error was incomplete recall of symptoms, particularly if they last
occurred many months before the questionnaire was completed. For this reason, we based
most of our analysis on pain and disability that was reported in the past month. An
exception was sickness absence, for which a longer time period was required to give
meaningful numbers of cases. However, we would expect spells of sickness absence to be
more memorable than more minor episodes of pain.
The prevalence of pain at most of the anatomical sites considered was somewhat lower than
has been recorded in UK workers who were surveyed using similar questions . For
example, low-back pain in the past month was reported by 28% of the Japanese workers as
compared with 28% in a sample of white UK office workers and 37% in a group of white UK
manual workers; while the corresponding figures were 21% v 26% and 23% for neck pain,
17% v 20% and 24% for shoulder pain, and 5% v 10% and 9% for elbow pain. More
remarkable, however, is the much lower prevalence of wrist/hand pain in Japanese workers
(7% v 30% and 23%). This lower prevalence extended to Japanese office workers (6% with
wrist/hand pain), most of whom were regular users of computer keyboards. The difference
in the prevalence of wrist/hand pain between Japanese and UK office workers was much
larger than that between manual and non-manual workers in the UK, or between white
workers in the UK and those of South Asian origin .
Also notable is the low rate of sickness absence that was attributed to regional pain
complaints. Overall, only 4% of study participants had been absent from work in the past
year because of low back pain, 2% for neck pain, 1% for shoulder pain, 0.3% for elbow pain
and 0.4% for wrist/hand pain. In comparison, reported rates in UK workers were more than
three times higher . Workers from Japan tend to claim compensation and take time off
work for illness attributed to occupation less often than their counterparts in the United
States . However, the differences we found are not explained simply by low overall rates
of sickness absence in Japan – 16% of participants reported absence in the past year
because of non-musculoskeletal illness. Rather the proportion of absence attributed to
musculoskeletal disorders was much lower than in the UK.
Earlier studies of musculoskeletal symptoms in Japan have focused mainly on low back pain
[10-22], with prevalence rates varying from 13% (in female nursing students ) to 83% (in
nurses ), according to the population studied and case definition. Where assessed, rates
of neck pain have been lower than those for low back pain in the same study [16-19], and
the prevalence of pain in the wrist or hand has been even lower [19,21].
Although there are many published surveys of regional pain in other countries, few studies to
date have compared rates of musculoskeletal illness between countries, using standardised
methods for data collection. In an analysis of data from surveys of the general adult
population in 10 developed and seven developing countries, the age-standardised
prevalence of chronic back pain was somewhat higher in developing countries (24.3%) than
in developed countries (18.5%) . A comparative survey of nursing personnel found a
higher 12-month prevalence of back complaints among Greek hospital nurses (75%) than in
Dutch nurses and caregivers employed in nursing homes (62%) . And in another study,
rates of pain among manual workers were substantially lower in Mumbai, India, than in the
UK, at each of five anatomical sites (low back, neck, shoulder, elbow and wrist/hand) .
For office workers, the differences were much smaller.
Within our Japanese sample of workers, analysis of risk factors for regional pain revealed
expected associations with stressful physical activities. However, associations with
somatising tendency were stronger, especially when pain was disabling. Given that the data
analysed were cross-sectional, it is possible that the observed associations between
physical activities and regional pain arose in part because of greater awareness, and
therefore more frequent reporting, of such activities among workers who found them painful.
It seems less likely, however, that the presence of back, neck or arm pain would cause a
person to over-report worry about somatic symptoms such as nausea, weakness, or
faintness and dizziness. Furthermore, in other countries, longitudinal studies have found
that somatising tendency predicted the future incidence and persistence of musculoskeletal
pain [3,4,25,26], and was associated with subsequent poor outcome in patients presenting to
primary care or treated by physiotherapy for musculoskeletal disorders [27-30]. Tendency to
somatise has also been associated with other complaints, including irritable bowel syndrome
 and report of symptoms following exposure to pesticides . In comparison with
somatising tendency, low mood was a much weaker risk factor for regional pain in the
In contrast, neither physical activity nor somatising tendency were clearly related to sickness
absence because of regional pain, which was associated much more strongly with absence
attributed to non-musculoskeletal disorders. It may be that in Japan, the major determinant
of variation in rates of absence ascribed to musculoskeletal symptoms is not differences in
the occurrence of such symptoms, but differences in workers’ general inclination to take
sickness absence when they perceive a health problem.
In summary, this study provides further evidence that the prevalence of musculoskeletal
symptoms varies importantly between countries, and suggests that, as in the UK, a major
risk factor for musculoskeletal complaint in Japan is tendency to somatise.
We thank Akiko Ishizuka, Ken Cox and Anna Cattrell for their assistance with data
Competing Interests: None declared
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Characteristics of participants by occupational group
Hours worked per week
Up to 20
Occupational activities in an average working day
Use of keyboard ≥4h
Other repeated movements of
Repeated bending and
straightening of elbow for ≥1h in
Work with hands above shoulder
height ≥1h in total
Lifting weights of ≥25kg by hand
Kneeling or squatting ≥1h in total
Satisfied with current job
Somatising tendency (number of symptoms in past week causing at least moderate concern)
0 170 28
1 237 40
≥2 183 31
n % n % % % n %
32.4 4 742
3 4 1
434 72 74 23 107 30 795 78 1410 62
73 12 5 2 15 4 343 34 436 19
38 12 873
329 55 91 28 108 31 589 49