Work-related musculoskeletaldisorders: are they truly declining?Sergio Vargas-Prada1,2,3

Occupational hazards have undergone sig-nificant changes since the middle of the20th century. In the past, workers wereexposed to serious chemical, physical andbiological hazards. However, with theimprovement of working conditions andreductions in harmful exposures, much ofthe morbidity and mortality attributableto those hazards has been reduced inhigh-income countries. Recently, attentionhas shifted to other disorders, rarelylethal and not exclusively caused by work,but which account for substantial costsand impact on workers’ well-being.1

Musculoskeletal disorders (MSDs) are apart of these ‘new’ work-related disorders.MSDs are a major cause of disability,2

affecting over 40 million West Europeanworkers, with direct costs in Europe esti-mated at between 0.5 and 2% of grossdomestic product.3 Minimising occupa-tional disability attributable to MSDs, andthe associated costs, is one of the majorchallenges in industrialised countries.

A growing body of evidence, basedlargely on administrative data, suggests adecline in the incidence of work-relatedMSDs over the past decade among peopleof working age in North America4 and inthe Netherlands.5 In this context, thestudy performed by Mustard et al,6 andreported in this issue of Occupational andEnvironmental Medicine, used threepopulation-based sources: (1) emergencydepartment records, (2) workers’ compen-sation claims and (3) samples from differ-ent waves of the Canadian health survey,to describe trends in the incidence ofwork-related MSDs in Ontario, Canadaover the period 2004–2011.

During the observation period, Mustardet al6 found that the incidence of non-traumatic MSDs, as determined from emer-gency records, lost-time compensation

claims and responses to the Canadianhealth surveys, decreased by 16%, 48% and42%, respectively. Moreover, a large dropof approximately 15% was observed in allthe three data sources between 2008 and2009 during the period of economic reces-sion that followed the onset of the globalfinancial crisis.At first sight this apparent decline in the

burden of MSDs linked with work seemsimportant news from a preventive perspec-tive. However, the observed trends mightsimply reflect a change in people’s propen-sity to attribute non-traumatic MSD tooccupation rather than a true reduction inrisk, or they could be driven by other non-measured causes.It may seem paradoxical that the decline

in incidence of non-traumatic MSDsshould accelerate during a time of a severeeconomic recession when work-relatedstress increases and employment is moreprecarious.7 As Mustard et al6 mentionedin their manuscript, it is possible that therewas a reduction in exposure to mechanicalloading in the workplace, either because ofergonomic improvements, or because thenumbers of exposed individuals reduced.However, randomised control trials ofergonomic improvements to prevent mus-culoskeletal pain have tended to demon-strate an absence of benefits.8

Other possible explanations for theobserved decline include the use of ‘casedefinitions’ based only on biomechanicalexposures at work, without consideration ofother exposures. Although it is generallyagreed that occupational physical activitiesare risk factors for common MSDs,9 arecent meta-analysis of longitudinal studieshas suggested that the risk of low back painis increased by only about 11% in workerswho lift weights of 10 kg by hand.9 Thisimplies that among people exposed to occu-pational lifting, only a minority of paincases could be ascribed to their work.Furthermore, exposure to physical activitiesat the workplace does not adequatelyexplain substantial variations between coun-tries,10 and over time within countries,11 inreported rates of musculoskeletal pain anddisability. In consequence, it is possible thatthe apparent decline of non-traumatic MSDobserved by Mustard et al6 might be anartefact of the influence of non-measuredvariables, such as exposure to psychosocial

aspects of the work environment, changesin individuals’ willingness to attend to emer-gency departments and differences in painthresholds, or in beliefs and expectationsabout pain causation and prognosis.

Another possible explanation of thisdeclining trend over time is that use ofadministrative data from workers’ compen-sation claims to describe trends in the inci-dence of work-related MSD results inunderestimation of the incidence rates.12

Even in industrialised countries, not allwork-related diseases or injuries result incompensation claims; and only employeeswho receive regular wages, pay taxes andhave certain rights, such as access to medicalcare or sick pay, are covered by workers’compensation schemes. It is also likely thatsome workers are less willing to claim forMSDs when they occur because they fearlosing their jobs or want to avoid reprisals.13

Improving surveillance of work-relatedMSD is a priority and, therefore, the studyreported by Mustard et al6 is very welcome.In order to understand more fully theapparently declining rates of non-traumaticMSD, we need to carry out repeated con-trolled epidemiological studies of physicalas well as psychosocial risk factors in whichoverall incidence, relative risks and attribut-able fractions are assessed for differentexposures.

Acknowledgements The author is very grateful toProfessor Fernando G. Benavides (Universitat PompeuFabra) and, Professor David Coggon (University ofSouthampton) and for their support and assistanceduring the writing of this commentary.

Competing interests None.

Provenance and peer review Commissioned;internally peer reviewed.

To cite Vargas-Prada S. Occup Environ Med PublishedOnline First: [please include Day Month Year]doi:10.1136/oemed-2014-102639

Received 4 November 2014Accepted 13 November 2014

▸ http://dx.doi.org/10.1136/oemed-2014-102442

Occup Environ Med 2014;0:1–2.doi:10.1136/oemed-2014-102639

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1Center for Research in Occupational Health (CiSAL),Universitat Pompeu Fabra, Barcelona, Spain; 2CIBEREpidemiología y Salud Pública (CIBERESP), Spain;3IMIM (Hospital del Mar Medical Research Institute),Barcelona, Spain

Correspondence to Dr Sergio Vargas-Prada, Centerfor Research in Occupational Health (CiSAL), UniversitatPompeu Fabra, Calle Dr Aiguader 88, 1ra planta,despacho 171.03, edificio PRBB, Barcelona 08003,Spain; sergio.vargas@upf.eduCommentary on the paper by Mustard et al.,Occup Environ Med, 2014.

Vargas-Prada S. Occup Environ Med Month 2014 Vol 0 No 0 1

Commentary OEM Online First, published on November 27, 2014 as 10.1136/oemed-2014-102639

Copyright Article author (or their employer) 2014. Produced by BMJ Publishing Group Ltd under licence.

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2 Vargas-Prada S. Occup Environ Med Month 2014 Vol 0 No 0

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they truly declining?Work-related musculoskeletal disorders: are

Sergio Vargas-Prada

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