"Human beings are the only species that deliberately deprive themselves of sleep for no apparent gain," Walker says. "Many people walk through their lives in an underslept state, not realizing it."

I think one of the myths out there is that we simply need less sleep as we age, and that's not true, in fact. We need just as much sleep in our 60s, 70s [and] 80s, as we do when we're in our 40s. It's simply that the brain is not capable of generating that sleep, which it still needs, and the body still needs. So, total amount of sleep actually decreases.