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

It has been associated with higher blood pressure, body mass index, and increased calcification of the coronary artery.

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.

• Every single cell of the body has clock genes, bits of DNA that flip on and off throughout the day.
• 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.

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.