Evaluation of cognitive performance in high temperature with heart rate: A pilot study

Real-time monitoring and evaluation of cognitive performance based on physiological indicators is a potentially new measure to ensure high air temperature safety. Heart rate might be an appropriate physiological indicator, yet it still needs several direct shreds of evidence. This study analyzed the relation between heart rate and cognitive performance at high air temperatures, based on the experimental data obtained from three phases of climate-controlled experiments. The climate-controlled experiments include five temperature levels of 26, 30, 33, 37, and 39 °C, and two relative humidity levels of 50% and 70%. During the experiments, eight cognitive tests were conducted to assess the basial cognitive performance, heart rate was continuously monitored, and the ratings of alertness and thermal sensation, comfort, and acceptability were documented. A total of 104 healthy subjects took part in the three phases of experiments, and 1478 valid samples were obtained. By analyzing the experimental data comprehensively, the results show that when the heart rate went up to 90bpm, the speed and accuracy of Stroop and d2 test would decline significantly(p < 0.05). The accuracy of Visual learning, Addition, Multiplication, and Typing only dropped significantly when the heart rate reach a level of 100bpm(p < 0.05). There was an inverted U-shaped relation between the relative accuracy of cognitive tests and heart rate. Based on the quadratic regression equation with a downward opening, the Heart Rate-Cognitive performance (HR-CP) model was built up. The R2 value of all regression equations is close to or greater than 0.8. These results suggest that heart rate might be a potential physiological indicator to evaluate the effects of high air temperature on cognitive performance.