Some who suffer from apnea know when they are waking up, some do not. It can even vary in the same person from night to night.

If something wakes you up more than once or twice (apnea or otherwise) you may find it becomes much harder to go back to sleep after that. Being awakened like that makes it difficult for the brain to relax. You kind of go into "something is wrong here" hyper vigilance mode. It's a remnant survival thing from back when we were sleeping in trees.

When this happens to me, I usually get up and go to another room and read quietly for 15-20 minutes then return to bed and try again. Meditation can help some folks. I haven't tried it myself but it kind of makes sense to me that it would help.

You often get a little shot of adrenaline when you wake up, especially if it's from apnea (which is essentially suffocation). That adrenaline takes a real toll on your heart and body. Which is one more reason why it's so important to treat it.

Not all apnea patients are overweight. Obesity can cause apnea for sure, but other things can, too. I asked my sleep doctor about this and he said while the majority of his patients are overweight, so are the majority of Americans. He said he had "more than a few" skinny patients with apnea, too.

The muscles that keep the airway open during sleep can lose tone (get weaker) with age. There are exercises and therapies that can sometimes strengthen them. That's the fundamental reason apnea occurs. Being overweight makes it worse because the fat tissue puts even more pressure on the airway, encouraging it to collapse.

Sleeping pills, alcohol, and the like are discouraged for apnea patients because it can make the apnea even worse. These drugs cause the airway muscles to relax even more.