Under the influence: An evaluation of the impact fatigue has on cognitive function of firefighters working 24 and 48-hour shifts

Abstract

The purpose of this research was to understand the impact fatigue has on cognitive function of firefighters working 24 and 48-hour shifts and to observe the extent of recovery that occurs between shift rotations. Data collected via actigraph, daily journal, and psychomotor vigilance tests were combined using date/time stamps to evaluate cognitive performance at various times of the day. Variables included demographic data, biometric data, subjective ratings of fatigue and sleepiness, objective measures of cognitive performance (PVT response times and errors), workload, sleep quantity and quality, and whether the participant was on or off shift. During this study participants slept an average of 5.3 hours while on shift and an average of 5.9 hours while not on shift. Results indicate there is a significant difference in the quantity of sleep obtained on and off shift (average of 32 minutes), but there is not a significant difference in the mean values of the cognitive performance between on and off shift. The mean value of cognitive performance both on shift (M=460ms) and off shift (M=456ms) is near the cutoff for what is considered normal response time (500ms). Additionally, an average of 25% (Range 22-27%) of the participants had mean response times greater than 500ms at all times of the day, both on and off shift. There were no significant differences observed in the objective measures of cognitive performance between groups with different years of experience, nor between groups that worked 24- or 48-hour shifts. Significant correlations between subjective fatigue ratings and objective measures of cognitive performance were only observed at noon and were inconsistent at all other times of the day. They reported feeling less fatigued and sleepy at noon, even though the objective measures of cognitive performance indicate a steady decline from the beginning of the day to the end of the day. Together these results may indicate firefighters are chronically fatigued, experiencing cognitive performance only slightly better than someone who is impaired by alcohol consumption, they may not be able recognize this impairment, and their performance is not improving on days off. Implementation of a fatigue management plan is recommended.