2006). Table 1 Demographic characteristics of the participants in Korean Working Condition Survey, 2006   Sample ( %)a Population ( %) Age group  15–24 5.4 7.4  25–34 23.3 23.7  35–44 32.0 27.7  45–54 25.0 23.5  55– 14.3 17.6 Sex  Men 57.9 58.0  Women 42.1 42.0 Education  Below middle school 19.7 24.3  High school 41.4 42.4  College/university

and beyond 38.9 33.3 Industry sectors  Agriculture, forestry and fishing 7.4 8.3  Mining and manufacturing 21.2 17.9  Construction Belinostat ic50 6.5 7.9  Wholesale and retail trade, hotels, and restaurants 19.8 24.8  Electricity, transport, telecom. and finance 11.4 10.0  Education 8.4 7.2  Other services 25.4 24.0 Total number “10,043” “23,447,000” aFigures of sample population are weighted Variables Sleep problems Sleep problems in this study Semaxanib ic50 were assessed by the single item ‘Do you currently suffer from work-related sleep problems (WRSP)?’ which is identical to the question

used in the EWCS. The response was either ‘yes’ or ‘no.’ Work organization factors Descriptions Prostatic acid phosphatase of work organization factors, response options, and response criteria are shown in Table 2. In all, 12 work organization variables were included in the questionnaire. The subjects were asked to answer ‘yes’ or ‘no’ about their experiences of discrimination regarding age and sex, sexual harassment, threat of violence, and violence at work during the past 12 months. Job insecurity, cognitive work demands, and emotional work demands were measured with a five-point scale. Job NVP-BEZ235 satisfaction and work-life

balance were measured with a four-point scale. Social support at work and work intensity were measured by the sum of two items, both with five-point scales. The Cronbach’s α for social support at work and for work intensity was 0.87 and 0.83, respectively. According to the report provided by KOSHA (Park and Lee 2006), the test–retest reliability for the 1-month interval for the items ‘working at very high speed,’ ‘working too tight deadlines,’ and ‘intellectually demanding work’ had 60.1, 61.7, and 68.5 % consistency rates, respectively.