Effects of Short Outdoor Walks on Indoor Cognitive Performance and Potential Countermeasures

During summer, office workers and students in Japan frequently transition between air-conditioned indoor spaces and hot outdoor environments. However, the impact of short outdoor walks on subsequent indoor cognitive performance remains unclear. This study examines how exposure to a heat-stressful outdoor environment affects cognitive performance in an air-conditioned setting.

A total of 96 participants completed a mathematical addition test before and after a 15-minute walk in an outdoor environment where the Universal Thermal Climate Index (UTCI) exceeded 44°C. The results showed a 3.6% decline in cognitive performance, measured as the percentage of correct answers relative to problems solved, following heat exposure. This decline was more pronounced in participants who had slept less than five hours, particularly among men. Sleep-deprived men exhibited the most significant cognitive impairment after heat exposure, highlighting the combined impact of insufficient sleep and heat stress.

To explore potential mitigation strategies, a follow-up field experiment with 46 participants assessed the effectiveness of shade from street trees and UV parasols. Cognitive performance remained stable after walking under street trees but declined by 1.3% in direct sunlight and 1.2% under UV parasols. These findings suggest that street trees effectively mitigate heat-induced cognitive decline, whereas UV parasols offer limited protection. Additionally, participants who had sufficient sleep experienced a smaller decline in cognitive performance, underscoring the importance of adequate sleep as a complementary protective measure.

This study provides key insights into environmental and behavioral strategies for maintaining cognitive performance in extreme urban heat, offering valuable guidance for urban planning and personal heat adaptation.