Associations between heat exposure, vigilance, and balance performance in summer tree fruit harvesters

Background: We sought to evaluate potential mediators of the relationship between heat exposure and traumatic injuries in outdoor agricultural workers. Methods: Linear mixed models were used to estimate associations between maximum work-shift Wet Bulb Globe Temperature (WBGT(max)) and post-shift vigilance (reaction time) and postural sway (total path length) in a cross-sectional sample of 46 Washington State tree fruit harvesters in August -September 2015. Results: The mean (SD) WBGT(max) was 27.4 (3.2) degrees C in August and 21.2 (2.0) degrees C in September. The mean pre-work-shift participant urine specific gravity indicated minimal dehydration. Twenty-four percent of participants exhibited possible excessive sleepiness. There was no association between WBGT(max) and post-shift reaction time or total path length. Conclusions: Heat exposure was not associated with impaired vigilance or balance in this study, in which the overall mean (SD) WBGT(max) was 25.9 (4.2) degrees C. However, the study identified opportunities to ensure adequate pre-work-shift hydration and to optimize sleep and work-shift timing in order to reduce occupational injury and heat-related illness risk. (C) 2017 Elsevier Ltd. All rights reserved.