High temperature impairs cognitive performance during a moderate intensity activity

Abstract

High temperatures are one of the main causes of work safety accidents associated with cognitive impairment. However, the effects of elevated ambient temperature on cognitive performance during moderate-intensity activities are unclear. In this study, subjects (N = 32) were exposed to four different air temperatures, i.e., 26, 30, 33, and 37 °C, and a relative humidity of 70% in a climate chamber. During the experiment, the subjects were required to complete neurobehavioral cognitive tests while walking on a treadmill with an estimated metabolic rate of 165 W/m2. During the 90-min experiment, the tympanic temperature, weight loss, heart rate, and percentage of adjacent inter-beat cardiac intervals differing by > 50 ms (pNN50) were measured. Subjective responses were collected using questionnaires.The accuracy of subjects’ responses to the semantic interference and visual perception tests were significantly decreased at 37 °C after 45 min of exercise. Additionally, over the exposure period at 37 °C, the accuracy of various cognitive tests also decreased, while the speed increased. The changes in the cognitive test results at 37 °C were associated with the elevation of the tympanic temperature, heart rate, dehydration rate, and decline of the pNN50. Similarly, the elevated thermal discomfort and intensity of neurobehavioral symptoms were related to these changes.In conclusion, exposure to a temperature of 37 °C for 45 min has a negative impact on the accuracy of personnel with moderate-activity intensity. Therefore, 45 min is recommended as a safe time for continuous work with moderate intensity at 37 °C.