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 problems.
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 [6
]. 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 [6
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 [6
]. 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 [9
]. 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
], with prevalence rates varying from 13% (in female nursing students [18
]) to 83% (in nurses [19
]), 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
], and the prevalence of pain in the wrist or hand has been even lower [19
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%) [23
]. 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%) [24
]. 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) [6
]. 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
], and was associated with subsequent poor outcome in patients presenting to primary care or treated by physiotherapy for musculoskeletal disorders [27
]. Tendency to somatise has also been associated with other complaints, including irritable bowel syndrome [31
] and report of symptoms following exposure to pesticides [32
]. In comparison with somatising tendency, low mood was a much weaker risk factor for regional pain in the Japanese workers.
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.
- 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 musculoskeletal complaints.
- 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.