Your summer lunchtime strolls may decrease your productivity

In a study published this month in Building and Environment, researchers from the University of Tsukuba discovered that just 15 minutes of walking outside on a hot day impaired cognitive performance, and this was most striking in men who don't get enough sleep.

Those who work or study in urban heat islands, such as Japan's large cities, typically have access to air conditioning during the summer months, which mitigates the detrimental effects of heat on learning and productivity. Nonetheless, brief exposure to hot environments during commuting or breaks is unavoidable, and it is unknown whether such exposure affects cognition. "Previous experiments have tested these effects using specialised climate chambers. In terms of radiation and wind, however, the outdoor thermal environment differs significantly from the indoor thermal environment, according to senior author Professor Hiroyuki Kusaka. "Radiation and wind exert important influences on thermal perception. Therefore, in order to evaluate the effects of outdoor heat stress on cognitive performance, outdoor experiments should be conducted."

During the Japanese summer, researchers simulated a scenario where workers or students leave an air-conditioned indoor environment to walk or take a break in a hot outdoor urban environment. 96 students completed a simple arithmetic test in a room with air conditioning before remaining indoors, walking outside, or resting outside for 15 minutes. They then returned indoors to complete a second arithmetic test, and any performance changes were measured. Walking in a hot outdoor environment impaired cognitive performance; however, exposure to the heat was not the only factor that contributed to this impairment. It was rather the combination of walking and being outdoors in the summer heat that had an effect on cognitive performance. Furthermore, this effect was more pronounced in sleep-deprived individuals, specifically men who had slept less than 5 hours.

"Japanese office workers and students, especially men, need to be aware of this situation as they work and study," says Kusaka. As the effects of climate change come to the fore, the team hopes that their findings will aid in the development of strategies to enhance the productivity and learning of workers and students in Japan, and possibly beyond.

Journal Reference: Yuki Asano, Yusuke Nakamura, Asuka Suzuki-Parker, Shohei Aiba, Hiroyuki Kusaka. Effect of walking in heat-stressful outdoor environments in an urban setting on cognitive performance indoors. Building and Environment, 2022; 213: 108893 DOI: 10.1016/j.buildenv.2022.108893