Effect of walking in heat-stressful outdoor environments in an urban setting on cognitive performance indoors

Office workers and students in Japan routinely move between air-conditioned indoor environments and heat stressful outdoor environments in summer. It is possible that a short walk in the outdoor environment affects workers' and students' cognitive performance. However, it is unclear. This study aimed to investigate the effect of walking in a heat-stressful outdoor environment on indoor cognitive performance. In the experiments, a total of 96 participants took a mathematical addition test in an air-conditioned room before and after walking in an actual outdoor environment. Results of the experiments showed that walking outdoors under heat-stressful conditions (UTCI >= 44 degrees C) for 15 min decreased the cognitive performance (percentage of correct answers to numbers of problems solved) by 3.6% compared with that before walking. An analysis focusing on the sleep duration showed a negative relationship between sleep duration and the decrease in cognitive performance. This tendency became particularly clear among the participants whose sleep duration was less than 5 h. The reduction of cognitive performance was more pronounced in male participants than in female participants. Sleep-deprived men who walk in a heat-stressful outdoor environment are more likely to exhibit poor cognitive performance when they return to an air-conditioned room. Japanese office workers and students, especially men, need to be aware of this as they work and study.