O13-4Exposure-response relationships between movements and postures of the wrist and carpal tunnel syndrome among male and female house painters: a retrospective cohorts study

Objectives To investigate exposure-response relationships between measured movements and postures of the wrist and the incidence of carpal tunnel syndrome (CTS), and any modifications by sex.Methods In 2011, we established a historical cohort of 9364 members of the Painters' Union in Denmark. Self-reported task distributions were obtained by questionnaire (53% responded) and combined with sex-specific task exposure matrices to get individual estimates of exposure intensity, i.e. velocity of wrist flexion/extension, mean power frequency (MPF), and non-neutral wrist postures. Exposure duration was assessed from yearly working proportions. Registered first time hospital discharge CTS-diagnoses and CTS-surgery were collected as outcomes. The cohort was followed 1994-2010. Log-linear Poisson regression was used.Results For CTS-diagnoses, the adjusted incidence rate ratios (IRRs) increased with increasing wrist velocity (IRR = 1.37 (95% CI: 1.10-1.71) per degree per second ( degree /s)) and MPF (IRR = 1.53 (95% CI: 1.21-1.91) per 0.01 Hz). For CTS-surgery the results were similar. The outcomes were not related to non-neutral postures or exposure duration. The adjusted IRRs for women were higher than those for men. There were no multiplicative interaction effects between exposure intensity, exposure duration and sex. However, the absolute IRs increased at a steeper rate for women than for men, indicating an additive interaction. Conclusions The incidence of CTS increased with increasing velocity of wrist flexion/extension and MPF of wrist movements. The relative increase in incidence rates were the same for women and men, but the absolute incidence rates increased at a steeper rate for women than for men.