Sleep misalignment and circadian rhythm impairment in long-haul bus drivers under a two-up operations system

Objectives: The objective of the study was to describe working and sleep conditions and to assess how sleep opportunities are associated with obtained sleep and alertness, in a sample of long-haul bus drivers working with a two-up operations system. Methods: Measures of subjective sleep and sleepiness, actigraphy, circadian temperature rhythm, and psychomotor vigilance tasks were obtained from a sample of 122 drivers from Argentina. Variables were compared between high and low fatigue risk groups, which were formed using a median split of a fatigue risk score. The score was calculated based on drivers' total working hours, maximum shift duration, minimum short break duration, maximum night work per seven days, and long break frequencies. Results: Considering a standardized one-day period, sleep in the bus accounted for 1.9 +/- 0.1 h of total sleep (57 1% efficiency), sleep at destination for 1.6 +/- 0.2 h of total sleep (90 +/- 1% efficiency), and sleep al home for 3.8+0.2 h of total sleep (89 +/- 1% nap efficiency and 90 1% anchor sleep efficiency). In drivers exposed to high-risk working schedules, the circadian temperature rhythm was weaker (lower % of variance explained by the model) (22.0 +/- 1.7% vs. 27.6+2.0%, p <0.05) and without a significant acrophase. Conclusions: Drivers obtained a total amount of weekly sleep similar to the recommended levels for adults, but distributed at different locations and at different times during the day. High-risk working schedules were associated with disruption of circadian temperature rhythms. These results point out to the need of the implementation of shift-work scheduling strategies to minimize sleep misalignment and circadian desynchronization in long-haul bus drivers. (C) 2020 National Sleep Foundation. Published by Elsevier Inc. All rights reserved.