Working hours and mental and physical fatigue in Japanese workers.
BACKGROUND
Establishing a threshold number of working hours is very important when making recommendations to protect people from the potentially harmful health effects caused by long working hours.


OBJECTIVE
To clarify the influence of working hours on both mental and physical symptoms of fatigue and use the data obtained to determine permissible working hours.


METHODS
Cross-sectional survey of male day-shift workers using the Self-Rating Depression Scale (SDS) and the Cumulative Fatigue Symptoms Index (CFSI). Working hours were subdivided into six groups and odds ratios were calculated for positive outcomes on the SDS and CFSI using logistic regression analysis.


RESULTS
A total of 715 workers participated. In the group working 260-279 h/month, the odds ratios for SDS and 'irritability', 'anxiety' and 'chronic tiredness' of the CFSI were significantly increased. In the group working >or=280 h/month, the odds ratios on CFSI for 'general fatigue', 'physical disorders', 'anxiety' and 'chronic tiredness' were likewise significantly increased.


CONCLUSIONS
The present results clarified that working hours should be <260 h/month in order to minimize fatigue symptoms in male day workers.
Department of Occupational and Environmental Medicine, Graduate School of Medicine, Chiba University, Chiba, Japan.
Shouji
S
Nagashima
Yasushi
Y
Suwazono
Yasushi
Y
Okubo
Mirei
M
Uetani
Etsuko
E
Kobayashi
Teruhiko
T
Kido
Koji
K
Nogawa
D000328:Adult; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D005221:Fatigue / Q000209:etiology*; D006801:Humans; D008297:Male; D005222:Mental Fatigue / Q000209:etiology*; D008875:Middle Aged; D009784:Occupational Diseases / Q000209:etiology*; D010561:Personnel Staffing and Scheduling; D013997:Time Factors; D014940:Work Schedule Tolerance / Q000523:psychology