Abstract

Low back pain (LBP) is a major cause of disability globally, and has been linked consistently with occupational activities that load the spine mechanically. However, randomised controlled trials of ergonomic interventions have failed to produce expected reductions in the disorder. Moreover, social security statistics from Britain reveal an eightfold rise in incapacity for work attributed to LBP during 1950–95 at a time when the physical demands of work were reducing.

To shed further light on this apparent paradox, a study (CUPID) was set up to assess differences in the prevalence of musculoskeletal pain and associated disability among workers carrying out similar occupational tasks in different cultural environments, and to explore explanations for any variation. Data were collected by questionnaire from 47 occupational groups (nurses, office workers and others) in 18 countries, with a follow-up survey after a mean interval of 14 months in 45 of the groups.

Analysis of baseline data indicated major variation in the prevalence of disabling LBP, with somewhat higher rates in nurses than office workers, but much larger differences between similar occupations in different countries. The variation was not explained by established risk factors, but correlated strongly with differences in the prevalence of disabling wrist/hand pain. Moreover, baseline extent of regional pain at anatomical sites outside the low back strongly predicted the prevalence of disabling LBP and associated sickness absence at follow-up, explaining much of the variation between occupational groups. These observations, which accord with findings from successive European Working Conditions Surveys, suggest that large international differences in the prevalence of LBP do not depend on causes specific to the spine, but are driven by factors that increase propensity to musculoskeletal pain more generally. Furthermore, a study of migrants from South Asia to the UK indicates that such propensity is environmentally determined, and can increase soon after moving to a new country where rates of pain are higher.

Based on current evidence, it can be hypothesised that while mechanical loading may cause minor strains that trigger episodes of LBP, the severity and persistence of symptoms is driven more by culturally-determined psychosocial factors that affect musculoskeletal pain more generally. If so, while ergonomics has an important role in enabling people to work more comfortably and to remain productive when limited by back pain, the key to reducing the continuing high burden of LBP may lie in understanding what drives differences in general propensity to musculoskeletal pain.