The Time in Bed (TIB) variable was obtained by
calculating the time from lights-out to the wake-up time. During
weekdays, the average time of lights-out was 23 h 52 (range between
22 h 22 and 01 h 05). The average wake-up time was
6 h 52 (range between 4 h 51 and 9 h 43).