Interesting article on NPR titled, “As Aging Brain’s Internal Clock Fades, A New Timekeeper May Kick In.” Here’s the operative paragraph:

We all have a set of so-called clock genes that keep us on a 24-hour cycle. In the morning they wind us up, and at night they help us wind down. A study out Monday in Proceedings of the National Academy of Sciences found that those genes might beat to a different rhythm in older folks.

These clocks are instrumental in providing us with the propensity to sleep. All this will be explained in my new book In Pursuit of Sleep to be published in early January 2016.