Evaluation of questionnaire-based information on previous physical work loads

Objectives The principal aim of the present study was to evaluate questionn aire-based information on past physical workloads (6-year recall). Methods Effects of memory difficulties on reproducibility were evaluated fo r 82 subjects by comparing previously reported results on current work load s (test-retest procedure) with the same items recalled 6 years later. Valid ity was assessed by comparing self-reports in 1995, regarding work loads in 1989, with worksite measurements performed in 1989. Results Six-year reproducibility, calculated as weighted kappa coefficients (k(w)), varied between 0.36 and 0.86, with the highest values for proporti on of the workday spent sitting and for perceived general exertion and the lowest values for trunk and neck flexion. The six-year reproducibility resu lts were similar to previously reported test-retest results for these items ; this finding indicates that memory difficulties was a minor problem. The validity of the questionnaire responses, expressed as rank correlations (r( s)) between the questionnaire responses and workplace measurements, varied between -0.16 and 0.78. The highest values were obtained for the items sitt ing and repetitive work and the lowest and "unacceptable" values were for h ead rotation and neck flexion. Misclassification of exposure did not appear to be differential with regard to musculoskeletal symptom status, as judge d by the calculated risk estimates. Conclusions The validity of some of these self-administered questionnaire i tems appears sufficient for a crude assessment of physical work loads in th e past in epidemiologic studies of the general population with predominantl y low levels of exposure.