[Sleep deprivation and its effect on the ability to maintain wakefulness: implications on functioning and driving]

During the last century, western society suffers from an increasing steep debt. A large number of accidents occur due to drowsy drivers. People are not aware of the influence of fatigue/drowsiness on their functioning and driving capacity.

Our goal is to identify and characterize measurable physioLogicaL information capable of monitoring simple and reliable performance of driver vigilance.

Eight healthy volunteers without sleep disorders were included in the study. They participated in two missions, on and off every two hours during 34-36 hours, in order to create an accumulative sleep debt. The tasks included the Maintenance of wakefulness test (MWT) and the driving simulator test. White tested, they remained connected to EEG, EMG, EOG, ECG and audio-video registration. These first results are related to 60 MWT tests.

The first falling asleep events (FA) appeared around the early afternoon hours, in agreement to the physiological tendency to fall asleep, according to the biological clock. The night was characterized by FAs with a very short sleep Latency time at around 4 AM. On the second day of the experiment, the averaged sleep latency was larger than in the night before, despite the accumulation of sleep debt. The fluctuations of RRI increased after the first micro sleep.

The autonomic nervous regulation displays an increase in the overall sympathetic activity as an indicator of increased stress. There is a correlation between parameters associated with instantaneous autonomic changes of heart rhythm (RRI) and the FA/almost-FA events observed on EEG. These attributes may provide a useful tool for monitoring drowsy drivers and preventing accidents.