Intra-Tour Variation of Firefighter Sleep Duration and Sleep-Wake Cycle within the 24/48 and 48/96 Shift Schedules

The purpose of this paper is to investigate intra-tour variation in total sleep time (TST) and sleep-wake cycle among US firefighters working the 24 hours on and 48 hours off shift schedule (24/48) and the 48 hours on and 96 hours off shift schedule (48/96).

Twenty-four firefighters were recruited for this sleep study and were evaluated over 18 days during a 24/48 shift schedule and again 6 months after firefighters transitioned to a 48/96 shift schedule. The primary outcome variables included TST, measured by actigraphy, and sleep-wake cycle (in-bed time and sleep offset) using the Emergency Services Sleep Diary.

Firefighters experienced intra-tour variations in TST and sleep offset. The least TST occurred at home prior to starting shift on the 24/48 and 48/96 schedules (5.80 hours and 5.66 hours, respectively). The second least TST occurred the night preceding shift end (5.84 hours and 5.81 hours, respectively). In contrast to in-bed time, sleep offset varied throughout the schedule and was found to correlate with TST. In addition, shift start/end time appears to be responsible for advanced sleep offset.

Results indicate that firefighters' sleep is complex and should not be reduced to singular averages. In both schedules, firefighters arrived at work with insufficient sleep, received insufficient sleep while on shift, and would commute home with insufficient sleep. These findings can inform future firefighter sleep research by accounting for intra-tour variations.