Work and neck/shoulder pain : risk and prognostic factors

This thesis presents the results from a population-based cohort study on risk and prognostic factors for neck/shoulder pain. The four papers in the thesis were based on a four to six year follow-up of both the cases and the referents from the MUSIC-Norrtälje baseline study, n = 2329. The main goals of this thesis were 1) to identify work-related exposures involved in the onset, and 2) to identify work-related exposures of importance for the prognosis of neck/shoulder pain. In Paper I, the study group consisted of employed subjects who at baseline and followup reported consistently pain in either the neck/shoulder or low back region. Four groups were identified: solely neck/shoulder pain, solely low back pain, concurrent neck/shoulder and low back pain, and migrating neck/shoulder and low back pain, n = 817. The results showed that the odds ratio for sickness absence was 1.69 (95% CI = 1.32-4.66) for those with concurrent neck/shoulder and low back pain, compared to the group with solely neck/shoulder or solely low back pain. In Paper 11, the study group consisted of employed subjects who had not sought medical care due to neck/shoulder pain at baseline, n = 1213. The results showed that 18% of the men and 29% of the women sought medical care due to neck/shoulder pain during the study period. For men, two single risk factors were identified. The relative risk (RR) for the onset of neck/shoulder pain was increased for manual handling ≥ 50 N ≥ 60 min/day (RR = 1.7, 95% Cl = 1.0-2.9), and for night work/shift work (RR = 1.7, 95% CI = 1.0-2.8). Moreover, the RR increased with an increasing number of exposures (RRs between 1.7 and 4.8). For women, no risk factors were identified. In Paper III, the study group consisted of employed subjects with self-rated neck/shoulder pain at baseline, n = 803. The results showed that at the follow-up 44% of the men and 33% of the women had recovered. For subjects exposed to sitting ≥ 75% of the working time, the relative chance for recovery (RC) was enhanced (RC = 1.32, 95% Cl = 1.0-1.7, and hampered for those simultaneously exposed to at least two of the following three biomechanical exposures: manual handling ≥ 50 N ≥60 min/day work with hands above shoulder level ≥ 60 min/day, or work with vibrating tools ≥ 30 min/day (RC = 0.61, 95% CI = 0.4-0.9). In Paper IV, the study group consisted of employed subjects who had sought medical care due to neck/shoulder or low back pain at baseline, n = 492. The aim was to study the effect of ergonomic interventions. The results showed that, in terms of pain intensity and pain-related disability, the prognosis for individuals who received educational worksite interventions was poorer than for those not receiving any interventions. The prognosis for individuals who received workplace interventions was similar to those not receiving any interventions. In conclusion, for men, work-related exposures influenced the onset of neck/shoulder pain, but no risk factors were identified for women. Work-related exposures influenced the prognosis, but ergonomic interventions were ineffective concerning the reduction in pain intensity and pain-related disability