Association between daily long working hours and actigraphic sleep, vigilance, blood pressure and psychological responses: a 10-day observational study among Japanese daytime workers.

Abstract

This study examined the association between daily long working hours (LWHs) and diverse health-related outcomes, using objective and subjective measures. It further evaluated the specific durations of daily LWHs that may be considered inappropriate in cases with adverse health effects. 98 employees participated in a 10-day observational study. Participants self-reported their daily working hours, subjective states and performed the measurement of blood pressure (BP) and psychomotor vigilance test (PVT) immediately on waking and before bedtime. Objective sleep was recorded nightly using actigraphy. Linear mixed model (LMM) analysis was performed. LWHs were significantly associated with higher systolic BP (β=0.65), greater fatigue (β=1.79) before bedtime, shorter total sleep time (TST; β=-0.09) and higher systolic BP (β=0.76) on waking (all p<0.05). Reduced TST was significantly linked to slower PVT reciprocal response time (β=0.03), higher lapse (β=-1.10) and greater sleepiness (β=-0.20) after waking (all p<0.05). Categorical LMM analysis revealed that working >12 hours was significantly associated with increased fatigue before bedtime, whereas working >13 hours significantly reduced TST compared to working ≤9 hours. Sleeping <6 hours caused significantly poorer PVT outcomes, and sleeping <5 hours caused significantly stronger sleepiness after waking than sleeping ≥7 hours. Daily LWHs and consequent reductions in sleep duration were associated with adverse outcomes. These findings underscore the importance of daily management of work hours and adequate sleep duration to prevent excessive workload and promote recovery from occupational demands.