Wearing a mask reduces cognitive performance at neutral temperatures: Evidence from climate chamber experiments on heat acclimatized subjects in China

While wearing a mask may reduce the risk of contracting respiratory infectious diseases, it may have some negative side-effects. Few studies have systematically explored whether current indoor comfort temperature standards still apply to the special situation of wearing a mask indoors. To address this issue, we conducted climate chamber experiments. The experimental settings included three temperature conditions (24 °C, 26 °C and 30 °C), and two mask conditions (wearing and not wearing a surgical mask). The relative humidity was maintained at 60 % in all 6 conditions. During the 170-minute mask-wearing period, the cognitive performance, physiological parameters and subjective assessments of 12 males and 12 females were compared in a repeated-measures experiment to explore the effects of temperature and mask-wearing. The results show that at a neutral temperature of 26 °C (but not at 24 °C or 30 °C), wearing a surgical mask significantly reduced speed in the multiplication test and accuracy in the Stroop test during some test periods, with increased cardiac variability and end-tidal carbon dioxide concentration suggesting that the mechanism for the effect was that wearing a mask had undesirable respiratory and cardiovascular consequences that caused our subjects to exert less effort. Wearing a mask did not affect the perceived air quality or the overall or local thermal sensation. The present results suggest that a slightly cool or slightly warm environment may have masked the impact of wearing a surgical mask, but more studies are necessary to confirm this observation.