Validity and reproducibility of self-reported working hours among Japanese male employees.
OBJECTIVE
Working long hours is a potential health hazard. Although self-reporting of working hours in various time frames has been used in epidemiologic studies, its validity is unclear. The objective of this study was to examine the validity and reproducibility of self-reported working hours among Japanese male employees.


METHODS
The participants were 164 male employees of four large-scale companies in Japan. For validity, the Spearman correlation between self-reported working hours in the second survey and the working hours recorded by the company was calculated for the following four time frames: daily working hours, monthly overtime working hours in the last month, average overtime working hours in the last 3 months, and the frequency of long working months (≥45 h/month) within the last 12 months. For reproducibility, the intraclass correlation between the first (September 2013) and second surveys (December 2013) was calculated for each of the four time frames.


RESULTS
The Spearman correlations between self-reported working hours and those based on company records were 0.74, 0.81, 0.85, and 0.89 for daily, monthly, 3-monthly, and yearly time periods, respectively. The intraclass correlations for self-reported working hours between the two questionnaire surveys were 0.63, 0.66, 0.73, and 0.87 for the respective time frames.


CONCLUSIONS
The results of the present study among Japanese male employees suggest that the validity of self-reported working hours is high for all four time frames, whereas the reproducibility is moderate to high.
Azbil Corporation Tokyo.
Teppei
T
Imai
Keisuke
K
Kuwahara
Toshiaki
T
Miyamoto
Hiroko
H
Okazaki
Akiko
A
Nishihara
Isamu
I
Kabe
Tetsuya
T
Mizoue
Seitaro
S
Dohi
D000328:Adult; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D010561:Personnel Staffing and Scheduling / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D057566:Self Report; D018709:Statistics, Nonparametric; D013997:Time Factors; D014937:Work / Q000523:psychology / Q000706:statistics & numerical data*; D016526:Workload / Q000523:psychology / Q000706:statistics & numerical data*