Audience member Carol tells Dr. Oz that no matter what time she goes to sleep, she always wakes up at 4am, which is contributing to her lack of sleep each night.

Dr. Oz responds by informing Carol that there are two types of insomnia; the insomnia where one can’t get to sleep, and the other insomnia where one wakes-up early no matter what time they went to sleep originally.

Dr. Oz further explains that the people who wake-up early have very strong circadian rhythms (referred to as a body clock, is an endogenously driven, roughly 24-hour cycle in biochemical, physiological, or behavioral processes), and they have a lot of hormonal shifts occurring those early hours. 

The issue of people not being able to get to sleep on-time is usually related to sleep hygiene issues, which as Dr. Oz explains, is related to the room not being cold enough, or from ambient noises.  Dr. Oz stresses  that the worse your sleep issues are, the colder your room needs to be.  If there are ambient noises bothering the sleeper, then those need to be eliminated as well.