A prospective cohort study of neck and shoulder pain in professional drivers

Introduction Epidemiological studies have provided strong evidence for an association between neck pain and awkward working postures [1]. There is also evidence for a causal relationship between highly repetitive work and neck and shoulder pain (NSP), and between neck disorders and forceful movements [1]. At present, epidemiological data are insufficient to provide support for a relationship of whole-body vibration (WBV) to NSP. Some studies have suggested that psychosocial factors at work and individual psychological distress may play a role in the development of NSP. The aims of this cohort study were to investigate the occurrence of NSP and the relation between NSP and individual- and work-related factors (WBV, physical load, psychosocial environment) in Italian professional drivers recruited in the EU VIBRISKS project [2]. Methods The study population included 537 male professional drivers of earth-moving machines, fork-lift trucks, and public utility vehicles. They were investigated over a two-year follow up period (2003-2006). Personal, occupational, and health histories were collected by means of the VIBRISKS questionnaire. NSP outcomes in the previous 12 months were treated as ordinal variables with four levels and assessed in terms of number of episodes (0, 1-5, 6-10, >10), duration (0, 1-6, 7-30, >30 days), and pain intensity (numerical rating scale (NRS) score: 0, 1-3, 4-5, 6-10). Cumulative WBV exposure was expressed as (awsi2ti) in m2s-4h, where awsi is the r.m.s. value of the vibration total value of the frequency-weighted accelerations measured on vehicle i driven for time ti in hours (hours/day  days/year  years). The following physical load factors were investigated: lifting (> 15 kg) with trunk bent or twisted, work with hands above shoulder level, driving with trunk bent or twisted. Psychosocial risk factors were expressed in terms of job decision, job support and job satisfaction. Psychological distress and psychosomatic symptoms were also investigated. The associations between NSP (ordinal) outcomes and individual- and work-related risk factors were expressed as proportional odds ratios estimated by random-intercept ordered logistic regression using time-lag models (i.e. NSP for subject i at time t (Yit) was related to predictor variable(s) k at time t – 1 (Xikt-1), i.e. the values of the predictors at one measurement earlier). Results At the initial survey, in the entire population of professional drivers the point prevalence of neck pain was 43.4%, and that of shoulder pain was 19.9%. The cumulative incidence rates for neck and shoulder pain over the follow-up period were 31.9 and 21.4%, respectively (Table 1). The incidence of high pain intensity (NRS score > 5) was 15.7% for the neck and 10.4% for the shoulder. At some points of the follow-up period there were cases of neck or shoulder pain who reported recovery from symptoms. As a result, the occurrence of persistent neck and shoulder pain in the study population (calculated over period prevalence) was 78.8 and 65.3%, respectively. After adjustment for potential confounders, cumulative WBV exposure was significantly associated with NSP outcomes (episodes, duration, intensity) over the follow-up period (Table 2). Frequent awkward postures while driving were significantly related to the frequency and severity of neck pain, while lifting with trunk bent or twisted > 45 min/day was associated with the duration of neck pain. Tasks involving prolonged exposures to lifting with awkward postures (>45 min/day) and work with hands above shoulder level (>1 h/day) were strongly associated with nearly all shoulder outcomes. Limited job decision and job dissatisfaction were significant predictors of episodes of neck pain over time, and low social support was related to pain intensity in the neck. Perceived psychosocial work factors were not significantly associated with shoulder outcomes even though there was some evidence for a positive trend. Psychological distress was strongly related to all NSP outcomes over the follow-up period. There were no significant interactions between work-related risk factors when appropriate product terms were included in multivariate data analysis. Conclusions The findings of this prospective cohort study tend to confirm that neck and shoulder outcomes are of multifactorial origin in a population of professional drivers. Cumulative WBV exposure, physical load factors and adverse psychosocial environment seem to contribute independently of each other to the development of neck and shoulder disorders in driving occupations. References [1] NIOSH. Musculoskeletal disorders and workplace factors – a critical review of epidemiologic evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. DHHS (NIOSH) Publication No. 97-141. Cincinnati, OH, 1997. [2] VIBRISKS. Final Technical Report. (www.vibrisks.soton.ac.uk).