Answers on the questionnaire were automatically imported,
manually checked for errors, and impossible values were corrected.
Analyses were performed for the group as a whole and separately
for the nine occupations. Descriptive statistics were presented as
the percentage, mean, and standard deviation (SD). The denominator
was corrected for missing values. All analyses were performed
with the statistical software IBM SPSS Statistics 20 (IBM,
Armonk, NY, USA).