Effect of Chronic Hyperthermia in Firefighters on Cognitive Function and Postural Stability

Purpose: The purpose of this pilot study is to measure the effect of chronic heat on postural balance characteristics and decision making by comparing firefighters with a long work experience to firefighters who have a much shorter work experience, in terms of years. Methods: Eight fulltime, male firefighters (33.92 years old ± 1.51) participated in this study. Firefighters perceived judgement of others’ fall risk was assessed while undergoing a functional magnetic resonance imaging (fMRI) as they viewed actors in various states of imbalance while walking or standing still. Firefighter’s postural balance was assessed with a wearable, inertial sensor system quantifying spatiotemporal parameters of gait as well as angular velocity, angular displacement, and angular acceleration for phase plane analysis along the medial-lateral (ML) and anterior-posterior (AP) planes. Participants performed static tests while on a force platform to assess these parameters during one-and two-feet balance tests with eyes open and closed. An instrumented timed up and go test (iTUG) was performed to assess dynamic parameters of gait and phase plane analysis. Firefighters perceived judgement of their own fall risk was determined during static and dynamic testing.Results: Firefighters were divided into two groups to compare firefighters with less than 8 years of work experience [Group 1: (3.00 years ± 2.83)] to firefighters with greater than 8 years [Group 2: (13.92 years ± 2.62)]. Between variance of double stance times during dual task was statistically significant (p = 0.013) between Group 1 (5.19e-04 ± (3.36e-04) and Group 2 (4.36e-3 ± (2.50e-03)). Firefighters who have worked more years (Group 2) have a larger variability between trials for the amount of time they have both feet on the ground during the double stance gait cycle. Significant associations (p-values ranging between 0.018 and 0.061) were found between gait dual task objective variables and gait PSPSI analysis, but not with respect to group. No significant correlations (p-values ranging between 0.165 and 0.980) were found between perceived judgement (as measured by PSPSI metric) of fall risk and history of firefighting. Significant associations (p-values ranging between 0.000173 and 0.100) were found between the two groups for static and dynamic postural balance. Postural sway analysis determined a significant increase in variance (p = 0.000173) along the AP plane for Group 1 firefighters (40.29 ± (1.32)) with less years of work experience in comparison with Group 2 (11.36 ± (7.83)). Variability may indicate central nervous system (CNS) impairments; however, a small sample size may be a contributing factor. Conclusions: Greater double stance variability during dynamic task for firefighters with more years worked may be due to underlying CNS impairments affecting postural stability. Nearly all firefighters portrayed similar concordance when comparing how they perceived fall risk of others revealing the number of years worked as a firefighter had no effect on their perception of fall risk. A consensus model was created from these curves to express a gold standard of perception to be used for future studies. Gait and postural sway results were inconclusive due to small sample size. Future studies are recommended.