In 2008, Mayo Clinic opened a Center for Sleep Medicine which treats various sleep disorders, including breathing disorders, restless legs syndrome, insomnia, parasomnias (nightmares, night terrors, sleep walking etc.), and circadian rhythm disturbances.

When you doze off, brain waves slow down.
There is occasional muscle twitching.
Breathing and heart rate slows down.
Body temperature drops slightly.

Deep sleep sets in.
Then the REM cycle kicks in.
Rapid Eye Movement. Brainwaves speed up and heart rate increases. You dream. Dreaming occurs. Breathing is rapid and shallow. You dream.

Six out of ten Americans have problems with sleep. Can't fall asleep or stay asleep. It may be due to high stress, poor sleeping environment, physical discomfort, or anxiety. And chronic sleep deprivation may lead to impaired cognitive function, ADHD, dizziness, headaches, nausea, and severe yawning.

Yawning. Yawning. Mayo says, don't use sleep aids unless really necessary -- they may cause bizarre behavior, such as nocturnal eating disorders.

For better sleep, the Mayo Clinic recommends:

Going to bed and waking up at the same time every day. Make your bedroom dark, quiet, cool. Get a comfortable mattress, and don't sleep with children or animals. Have a relaxing routine before bed - such as reading. Or sex. Go to bed when you're tired and turn out the lights.

(Reading. Sex. Reading about Sex. Reading during Sex. Sex.)