I usually get about 7 hours of sleep per night.
I have sleep apnea and understand the importance of 'real' sleep. I've read many articles on sleep. I've even found some articles that state that the body can actually 'bank' sleep. I like to take naps on the weekends because I never know how much true sleep I will get at night. Without my CPAP machine I stop breathing for more than 30 seconds at a time, an average of 29 times per hour.
When a person that has sleep apnea has that happen they can actually be on the edge of slipping into a therapeutic sleep state and all of sudden stop breathing. The brain then wakes the body up to say "Hey, you're not breathing." The apnea sufferer doesn't even know that their body has woken up. They just drift off again and just hit that edge and stop breathing again. This cycle can continue on all night and the sleep apnea sufferer can wake up even after 10 hours of sleep feeling completely exhausted.
My CPAP machine (Darth Vader mask as I refer to it so I don't think I look so dorky while wearing it in my sleep) has really helped. It provides a positive air flow to keep my airway open an night and I get a more relaxing sleep. Sometimes it feels uncomfortable to wear but the overall benefits are worth it. The best feature is that my CPAP machine has a built in humidifier so I never wake up with that 'dry' throat or sinuses anymore.
My wife now gets better sleep as well because she doesn't have to listen to me snore all night.