Background: Although it has recently been recognised that inflammation is important in the development of work-related musculoskeletal disorders (MSDs), the exact pathophysiological pathways are unknown.
Methods: We investigated serum concentrations of inflammatory cytokines in 35 female supermarket cashiers with repetitive work tasks and work related neck/shoulder complaints, compared with those from 25 women without MSDs (6 supermarket cashiers and 19 middle-school teachers or faculty staff). None of the subjects were pregnant or lactating, and showed no signs of rheumatoid arthritis, systemic lupus erythematosus, cancer, diabetes, coronary artery disease or inadequately controlled hypertension. Serum levels of IL-1α, IL-1β, IL-6, IL-8, IL-10, IL-12, MCP-1, MIP-1α, MIP-1β, TNF-α, GM-CSF, CTGF and CRP were analysed.
Results: The women with pain related to MSD had higher serum concentrations of MIP-1β (median, 25th-75th percentile: 90.0 pg/mL, 62.5-110 vs. 73.1 pg/mL, 54.6-88.3; p = 0.018), IL-12 (0.26 pg/mL, 0.26-0.26 vs. 0.26 pg/mL, 0.26-0.26; p = 0.047) and CRP (0.5 mg/L, 0.5-1.6 vs. 0.5 mg/L, 0.5-0.5; p = 0.003), than control subjects. Levels of MIP-1α, MIP-1β and CRP were correlated with the reported intensity of neck/shoulder pain (r = 0.29, p = 0.03 for MIP-1α; r = 0.29, p = 0.02 for MIP-1β and r = 0.43, p = 0.001 for CRP). No statistically significant differences in serum levels were found for the remaining cytokines.
Conclusions: Otherwise healthy females with ongoing work-related neck/shoulder pain showed higher serum concentrations of MIP-1β, IL-12 and CRP than controls, and the levels of MIP-1α, MIP-1β and CRP were correlated to pain intensity. These results support previous findings that inflammatory processes play a part in work related MSDs.