0136 Firefighter Sleep Behavior and Psychomotor Vigilance Compared to Biomathematical Predictions of Performance

Abstract

Abstract Introduction Firefighters work a demanding 24-hour job in which fatigue may compromise safety. Biomathematical fatigue modeling software applications, like the Sleep, Activity, Fatigue, and Task Effectiveness Fatigue Avoidance Scheduling Tool (SAFTE-FAST) could be adapted to serve as a fatigue mitigation tool for firefighting operations. SAFTE-FAST predicts task effectiveness using objective work and sleep data. Model predictions of effectiveness (Predicted Effectiveness) have not been previously compared against actual Psychomotor Vigilance Task (PVT) speed (Actual Effectiveness) in a firefighter population. Methods Total sleep time across the 24-hour day (TST24) was monitored continuously throughout a 2-week study period in firefighters working 24-hour shifts using a sleep-tracking actigraphy device (Zulu Watch, Institutes for Behavior Resources). Speed on an 8-minute PVT was assessed daily on on-shift and off-shift days. Mean speeds >2 standard deviations above the grand distribution were excluded. SAFTE-FAST calculated Predicted Effectiveness (PVT Speed [1/Reaction Time] expressed as a % of individual optimum performance) from objective sleep and work data. Actual Effectiveness was computed as a percentage of the median of an individual’s top 10% fastest PVT Speeds. Paired samples t-test explored differences between on-shift and off-shift PVT Speed and TST24. Linear regression explored correlation of Predicted Effectiveness to Actual Effectiveness across 5% Effectiveness bins. Results Two hundred twenty (N=220) firefighters provided sleep, work, and PVT data for 1-2 weeks (Mean: 8; Range: 1-15 days) between 9/2020 to 8/2021. On-shift days accounted for 37% of study days (M: 3; R: 0-10 on-shift days). PVT Speed and TST24 were not significantly different between on-shift (Speed: 2.43±0.47; TST24: 404±163 minutes) and off-shift days (Speed: 2.44±0.48; TST24: 396±156 min; all p>0.1). Linear regression across 5% SAFTE prediction bins revealed significant correlations between SAFTE Predicted Effectiveness and PVT Actual Effectiveness (R2=0.861, p<.001). Conclusion Firefighters averaged less than 7 hours of sleep per 24-hour period whether on or off-shift. Average PVT speed was similar to performance from chronically-sleep-deprived or alcohol-impaired individuals. SAFTE-FAST Predicted Effectiveness and PVT Actual Effectiveness were distributed similarly across 5% bins. While preliminary, these findings suggest that firefighters may suffer from chronic sleep debt and impaired psychomotor vigilance that can be predicted using biomathematical modelling. Support (If Any) N/A