body temperature

“In order to fall asleep and stay asleep, you need your body temperature to be about one to three degrees lower than it was in that in the afternoon.”

“Alcohol actually lowers your body temperature, but your perception of that lower body temperature is disrupted. So part of the reason you can fall asleep When you drink alcohol is because it lowers your body temperature.”

“Second to light temperature is the most powerful stimulus for wakefulness. Actually, when you wake up in the morning, it's because your body temperature is rising.”