3. Results
3.1. Response and respondents’ characteristics
In 2010, a total of 1,551 respondents returned a questionnaire
eligible for analysis (34%; 1,551/4,500). In 2013, 421 respondents
were either no longer employed in the construction industry, retired,
deceased, or no longer approachable for the follow-up measurement
for other reasons. A total of 1,130 workers were sent the follow-up
questionnaire and 713 returned a questionnaire eligible for analysis,
resulting in a net response rate of 63% (713/1,130) for the followup.
These respondents’ characteristics are presented in Table 1