In contrast to that, Viikari-Juntura et al. (1996) reported an increased risk of buy PF299 reporting high workload for forest industry workers having severe low back pain, e.g. for kneeling and squatting (OR, 1.6; 95 % CI, 1.2–1.9). Again, sample size was small (18 subjects with and 18 subjects without low back pain), and squatting or kneeling was rare in both groups (median, 0.0 h each). As the present study has dealt with knee complaints, our results cannot be closely compared to those studies. Moreover, our study concentrated on kneeling or squatting tasks (median, 32.7 min
or 29.7 % (0.0–92.7) of knee postures per measurement). With certain constraints, it should be noted that subjects with severe knee pain probably did not participate in our study due to sick leave. Study limitations The present study has several limitations that should be considered when interpreting the results. The study was based on the voluntariness of participation of companies and subjects, which might have
led to selection bias. Moreover, we examined only tasks where we expected knee-straining postures. Thus, our results are not representative for the whole working content of the examined trades. While in survey t 0 all measured subjects filled out the questionnaire, in survey t 1, only 65.8 % of the participants responded. However, compared to response-rates of other studies in Germany, this can be seen as check details quite successful (Latza et al. 2004). A non-responder analysis yielded similar to identical characteristics for responders and non-responders (see Appendix B in Supplementary Material). This lack of difference suggests that the lost to follow-up may not be an important issue, and the risk of a non-responder bias may be ruled out. As the second survey was conducted by mail, study participants were only able Sclareol to ask comprehension questions in the first survey when study staff was on site. Thus, comprehension problems
may have occurred in the second survey more often and may have biased the exposure assessment, for example by self-reported exposure wrongly related to a whole work shift, rather than to the measuring period. However, we attempted to minimise this effect by using the same questionnaire as in the first survey, accompanied by information on how to correctly fill it out. In addition, we gave a short description of the work Duvelisib ic50 performed during the exposure measurement at t 0. This procedure could have artificially reduced recall bias as such information cannot be provided in an epidemiological study, for example. Our survey covered a pre- and post-period of 6 months, while in reality, there are mostly several years or decades between exposure and retrospective assessment.