PAIN 155 (2014) 847–848
Work and multisite musculoskeletal pain We know that certain physical exposures at work are associated with painful conditions at particular anatomical sites. However, less is known about the relationship between exposures at work and multisite pain. A study by Herin and colleagues, reported in this issue of PAINÒ , contributes to ﬁlling this gap. The study investigated the relationship between psychosocial and physical factors at the workplace, and the subsequent development of musculoskeletal pain, in a sample of almost 7000 subjects from a working population. Herin et al. report that multisite musculoskeletal pain was common in their sample of working subjects, affecting a quarter of those who reported musculoskeletal pain in 1995 after being pain free in 1990. Different risk factors were found to be associated with multisite pain in women and men. For example, the psychosocial factors of psychological demand and decision latitude were signiﬁcantly associated with pain at 3 or 4 sites in women but not men, and forceful effort was signiﬁcantly associated with pain at 4 sites in men only. With previous work in occupational epidemiology having focussed largely on the relationship between exposures and pain at speciﬁed anatomical locations, especially when there is a mechanism that supports causality, the study by Herin et al. underlines that multisite pain in working populations may need more attention. Other recent evidence points in the same direction. For example, studies from Finland demonstrated that multisite pain is a strong predictor of work ability and absence from work [2,3,10]. Fibromyalgia, a condition characterized by pain at multiple sites, can profoundly interfere with ability to work, and treatment that effectively reduces pain can be expected to have also a signiﬁcant impact on work ability . What is particularly interesting is that in the logistic regression analyses presented in Table 2 of the study by Herin and colleagues, the statistically signiﬁcant associations between physical and psychosocial work-related factors and pain at speciﬁed body sites (neck/shoulder, elbow/forearm/hand, low back, hip/knee/foot) did not exceed hazard ratios of 2, ie, falling short of a doubling of the risk due to factors at the workplace. When Herin and colleagues investigated multisite pain (pain at 3 or 4 anatomical sites; their Table 3), they found several signiﬁcant associations with hazard ratios larger than 2. The doubling of risk is important in occupational medicine, in particular with regard to recognizing a condition as an occupational disease. Consider a condition that can result from occupational and nonoccupational causes, and consider further that causation cannot be determined with certainty in any individual case. If an exposure at the workplace more than doubles the risk of disease, then any individual patient with such an occupa-
tional exposure will be more likely than not to have an occupational cause for the condition. When the status of having an occupational disease is determined on the balance of probabilities, exceeding this doubling of risk is crucial. Perhaps we will need to consider multisite pain as an occupational disease in the future, but ﬁrst the ﬁndings reported by Herin et al., especially with regard to the magnitude of the hazard ratios, will need to be corroborated by other investigators. As we have mentioned, there were interesting differences in the relationships between workplace exposures and subsequent pain between women and men: only in women were the psychosocial factors psychological demand and decision latitude found to be signiﬁcantly associated with elbow, forearm, or hand pain and with pain at 3 or 4 anatomical sites. One study is not enough to convince us that these gender-speciﬁc differences are real and hold true in other populations but, should these gender differences indeed be conﬁrmed, this suggests that gender may be a factor to consider in guiding preventive efforts and in assessing whether a condition is occupational in origin. Again, future work will need to conﬁrm that these gender-speciﬁc differences are in fact real. The study performed by Herin and colleagues has several strengths, including the comparatively large sample size, the examination of subjects by occupational physicians, and the inclusion in the analysis of a number of physically demanding work characteristics as well as psychological components of the work environment. A possible drawback is that the data were from the 1990s. The work environment has not been static since then, but the general principles should still apply. Also, a principal limitation of this type of occupational epidemiology is the detail or lack of detail possible in the description of the exposures encountered at the work place. For instance, exposure to vibration was assessed and is further described in the paper as exposure to considerable vibrations or exposure to jolts. Taking vibration exposure as an example, it would have been informative to be more speciﬁc and differentiate between vibration primarily affecting the hand and arm vs whole-body vibration. Both types of vibration exposure may occur at the workplace and there are painful conditions associated with both of them, but at different body sites, and so they should not be viewed as the same. Whole-body vibration has been linked to back and neck pain [6,8,9]. Vibration affecting the hand and arm has been linked with hand-arm vibration syndrome and carpal tunnel syndrome, both of which can result in hand pain [1,4,7,11,13]. Limitations notwithstanding, the study by Herin and colleagues published in this issue of PAINÒ advances our understanding with regard to musculoskeletal pain, especially multisite pain, its
DOI of original article: http://dx.doi.org/10.1016/j.pain.2014.01.033
http://dx.doi.org/10.1016/j.pain.2014.02.018 0304-3959/Ó 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.
Commentary / PAIN 155 (2014) 847–848
associations with physical and psychological factors at work, and possible gender differences. Conﬂict of interest statement The author has no conﬂict of interest to declare. Acknowledgment The author thanks Sheena Derry and R. Andrew Moore for comments. References  Andréu JL, Otón T, Silva-Fernández L, Sanz J. Hand pain other than carpal tunnel syndrome (CTS): the role of occupational factors. Best Pract Res Clin Rheumatol 2011;25:31–42.  Haukka E, Kaila-Kangas L, Luukkonen R, Takala EP, Viikari-Juntura E, LeinoArjas P. Predictors of sickness absence related to musculoskeletal pain: a twoyear follow-up study of workers in municipal kitchens. Scand J Work Environ Health 2014 [Epub ahead of print].  Haukka E, Kaila-Kangas L, Ojajärvi A, Miranda H, Karppinen J, Viikari-Juntura E, Heliövaara M, Leino-Arjas P. Pain in multiple sites and sickness absence trajectories: a prospective study among Finns. PAINÒ 2013;154:306–12.  Heaver C, Goonetilleke KS, Ferguson H, Shiralkar S. Hand-arm vibration syndrome: a common occupational hazard in industrialized countries. J Hand Surg Eur 2011;36:354–63.  Herin F, Vézina M, Thaon I, Soulat J-M, Paris C, ESTEV group. Predictive risk factors for chronic regional and multisite musculoskeletal pain: A 5-year prospective study in a working population. PAINÒ 2014;155:937–43.
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Sebastian Straube Institute of Occupational, Social and Environmental Medicine, University Medical Center Göttingen, Waldweg 37 B, D-37073 Göttingen, Germany ⇑ Tel.: +49 551 398044; fax: +49 551 396184. E-mail address: [email protected]