EP3671757A1 — System and method for determining a level of alertness

USPTO Abstract

A system is provided for determining a level of alertness of a subject, using a physiological sensor for providing physiological sensor signals which distinguish between a sleep state and an awake state of the subject. Sleep sessions are identified and their associated falling asleep and waking up times. A single representative midsleep time is obtained from multiple sleep sessions over a 24 hour period, and a circadian phase is estimated using the single representative midsleep time. A level of alertness is then obtained from the circadian phase. This system avoids the need for the use of a default circadian phase when determining a level of alertness. The system can more accurately estimate sleepiness for individuals that have irregular sleep patterns such as shift workers or people with sleep disorders. The single representative midsleep time is also able to take account of multiple sleep sessions, i.e. naps or periods of restless sleep.