Figure 1
Flow diagram of the participants through the phases of the trial. 1 Workers who were loss-to-follow- up due to non-responding were included again in the following measurements. To illustrate; at three months follow-up, 27 workers did not respond to the questionnaires of whom 18 of them were non-responders. At 6 months questionnaire, 103 (95 +18 workers) workers were approached, and 89 workers responded to  this questionnaire. a Non-responders was defined as workers that did not complete a particular follow-up measurement. b Loss-to-follow up was defined as workers that ended participation in follow-up measurements (i.e., drop outs).