Around 30 to 50 percent of people sleep between the hours of 11 pm and 7 am. Another 40 percents are either slightly morning people or slightly evening people.To understand why some people are early birds while others are night owls, we have to take into consideration the body's circadian system.

Your Body is a Clock

The body is an orchestra of organs, each providing an essential function. In this metaphor, the circadian rhythm is the conductor. The conductor makes every neurotransmitter, every hormone, and every chemical in the body cycle with the daily rhythm.This makes us our sleep habits unique and tailored.

Early Bird or Night Owls

Being a morning (or evening) person is inborn, genetic, and very hard to change.

Sleep Habits

It has been associated with higher blood pressure, body mass index, and increased calcification of the coronary artery. <ul><li>In lab experiments, people who slept only five hours a night for one week became less sensitive to insulin, which makes it harder to maintain blood sugar levels. </li><li>In an overnight sleep study of 1,024 individuals, poor sleep was associated with the misregulation of the hunger hormones leptin and ghrelin.</li></ul>

Less Sleep is dangerous

When our personal clock is out of sync with the one of our society, our health suffers.

Social Jet Lag

<ul><li>Every single cell of the body has clock genes, bits of DNA that flip on and off throughout the day. </li><li>Like the body as a whole, the cell's metabolism is scheduled for efficiency. Clock genes regulate the expression of between 5 and 20 percent of all the other genes in the cell.</li></ul>

Tick Tock

If Cassidy Sokolis ever needs to wake up before 11 am, she scatters three alarm clocks throughout her bedroom. Even then, she still often sleeps through the clamor. "It's really frustrating," Sokolis, a 21-year-old junior at Northern Arizona University, tells me. "People have mocked me for it, saying how lazy I am, that I'm not trying hard enough.