Table 2.
Proportions of subjects with long overtime work hours, Spearman correlations between self-reported working hours and company records of working hours, and intra-class correlations of self-reported working hours between the first and second surveys for the four time frames
| Proportions of subjects with long overtime work hours*, % | Overtime working hours of official records** | Validity† | Reproducibility‡ | |||||
|---|---|---|---|---|---|---|---|---|
| Self-reported working hours | Official records | Spearman correlation | p-value | Intra-class correlation | p-value | |||
| First survey | Second survey | |||||||
| *Defined as 10 or more working hours per day (daily working hours), 45 or more hours of overtime work in the last month (monthly overtime work hours in the last month), 45 or more hours of overtime work on average in the past 3 months (monthly overtime work hours in the past 3 months) and 8 months/year or more of long working months (frequency of long working months within the last 12 months). The proportions of subjects in each category for the four time frames were shown in Supplement Table 1.
** Data for continuous variables are expressed as median (IQR) for daily overtime working hours (daily working hours), monthly overtime working hours (monthly overtime work hours in the last month), average monthly overtime working hours in the past 3 months (monthly overtime work hours in the past 3 months) and average monthly overtime working hours in the past 12 months (frequency of long working months within the last 12 months). †Spearman correlation and p-value for correlations between self-reported working hours and company records of working hours. ‡Intra-class correlation and p-value for correlations of self-reported working hours between the first and second surveys. §Defined as 45 h or more of overtime work in 1 month. | ||||||||
| Daily working hours | 45.1 | 39.0 | 34.2 | 1.7 h/day (0.3-2.5) | 0.74 | <0.01 | 0.63 | <0.01 |
| Monthly overtime work hours in the last month | 45.1 | 29.3 | 31.7 | 32.3 h/month (6.3-46.7) | 0.81 | <0.01 | 0.66 | <0.01 |
| Monthly overtime work hours in the last 3 months | 41.5 | 37.2 | 39.6 | 38.5 h/month (17.1-53.6) | 0.85 | <0.01 | 0.73 | <0.01 |
| Frequency of long working months§ within the last 12 months | 17.7 | 16.5 | 18.3 | 38.2 h/month (15.4-54.3) | 0.89 | <0.01 | 0.87 | <0.01 |