Evaluation of dynamics of forehead skin temperature under induced drowsiness

Drowsiness is one of the leading causes of traffic accidents. A technique for fast and easy measurement of the level of drowsiness is desirable. The objective of the present paper is to evaluate the dynamics of forehead skin temperature (FHT) under induced drowsiness. With a precursory change associated with drowsiness from the FHT, which is a noninvasive measurement, drowsiness can be detected at an early stage and, possibly, traffic accidents can be prevented. In this study, the measured FHTs were categorized into five drowsiness levels according to facial expressions (Level 1 is awake and Level 5 is extremely drowsy). In an experiment, the thermoregulation process of drowsiness was represented by a decrease in the total peripheral resistance, elevation of the nasal skin temperature, and decline in the tympanum temperature. The experimental results showed a significant decrease in FHT for drowsiness Levels 3–5 compared to the rest state (Mann–Whitney U‐test, p < 0.01). Because FHT did not increase in accordance with the process for nasal skin temperature, FHT could represent both skin and core temperatures. The results suggest that FHT can be an indicator for predicting drowsiness. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.