The concurrence of musculoskeletal pain and associated work-related factors: a cross sectional study.

BACKGROUND: Several recent studies have described the presence of musculoskeletal complaints, presenting evidence that multisite musculoskeletal pain (MP) is more often present than single-site musculoskeletal pain. However, less is known about determinants of this multimorbidity, particularly, concerning the role of occupational factors and, mainly, what determines single or multisite pain. This study described the associations between pain in different body sites and investigated related factors to MP in workers from Brazil.

METHODS: A total of 1070 workers (228 women and 842 men), from urban cleaning services and from shoe manufacturers, participated in this cross sectional study (response 97 %). Interviewer-administered questionnaire included sociodemographic factors, physical and psychosocial work demands, leisure-time activities and musculoskeletal pain which was presence of pain in previous seven days, considering eight body sites and MP, the sum score of all painful sites, varying 0-8. A factor analysis was performed that captured the nine variables of physical exposure into two latent factors. Associations of pain between different body sites were assessed. Cox regression analyses, presenting the prevalence ratio (PR), showed the related factors to MP.

RESULTS: In the previous seven days, 30 % of workers had MP. For all body sites, comorbidity ranged from 72 % to 91 %. Having pain in one body site is associated with pain in other site and the associations between proximal sites were stronger than between more distal sites. High exposure to manual material handling and awkward postures (PR = 1.5, 95 % CI 1.1-2.0), job strain (PR = 1.2, 95 % CI 1.0-1.6), and low social support (PR = 1.3, 95 % CI 1.0-1.7) and being woman (PR = 1.7, 95 % CI 1.3-2.3) were associated with MP. Risk factors for single-site pain and for subsequent musculoskeletal comorbidity were very similar, suggesting an additive effect of risk factors.

CONCLUSIONS: Most workers reported MP that was associated with several work-related factors. The findings support the idea that multisite pain is a continuum of single-site pain, maintained by exposure to several risk factors, rather than the result of a specific risk factor that initiates the multisite pain but not single-site pain. Workplace interventions are needed to decrease the number of pain sites, in order to improve the worker's health.