Nagaya T, et al. - This study intended to examine inter-relationships among working hours, sleep duration and headache. The clinicians demonstrated that even in apparently healthy white-collar men, long working hours directly and indirectly (via short sleep duration) induced headache. Among employees, headache could be useful for early detection of adverse health effects by long working hours.

• The clinicians performed this cross-sectional analyses for prevalent headache (n = 35,908) and 1-year follow-up analyses for incident headache (n = 19,788) in apparently healthy white-collar men aged 25–59 years.
• In this study, headache (yes/no), working hours and sleep duration were based on self-administered questionnaire.
• Logistic regression analysis estimated odds ratio (OR) and 95% confidence interval for prevalent and incident headache according to working hours (35-44, 45-49, 50-59 and ≥60 h/week) and sleep duration (≥7, 6-6.9, 5–5.9 and <5 h/day), and tested linear trends in OR, after determination of relationships between working hours and sleep duration.
• Furthermore, they checked interactive effects of working hours and sleep duration on OR.
• In the analyses, covariates were age, body mass index, drinking, smoking and exercise.

• The clinicians found prevalent and incident headache in 1979 (5.5%) men and 707 (3.6%) men, respectively.
• They observed an inverse association between working hours with sleep duration.
• Regardless of influences of the covariates, OR for prevalent and incident headache rose with increasing working hours and with reducing sleep duration.
• For prevalent or incident headache, working hours and sleep duration had no interactive effects on OR.