- amount of time spent awake
- genetic factors
- our age
- our circadian rhythm which starts the process of sleep
It is true, a newborn does just one of three things- they eat, they poop and they sleep. In fact, new born babies spend more than half of their time asleep. Over the first 5 years of life, the amount of sleep one requires goes down, and then again in the teenage years and finally when an individual turns age 50.
There are two types of people- the ones who like to stay up and then the ones who like to go to bed early. The “night owls” have a natural inclination to stay up late and function better in the latter part of the day. As opposed to the “early birds” who wake up early, go to bed early and function best in the beginning part of the day. Most people tend to fall in the middle of these two extremes. The differences are genetically caused – specifically by circadian genes.
Source: Sleep Your Questions Answered, April 2007 by Renata L. Riha, MD