I know one of the problems with Sleep Apnea sufferers was they don't get as much deep or REM sleep. When they stop breathing for a certain amount of time, a defense mechanism partially wakes the person up, and then resumes breathing. It doesn't wake them up completely, but certainly kicks them out of REM or deep sleep. Now repeat this several times a night, and you get a similar effect to sleep deprivation. The sufferers have very little energy, feel tired all the time, increased stress etc.
I've met somoene that had it, and he just said that you can sleep 8 hours + and still wake up tired, like you hardly slept at all.
I don't know much about the other stresses on the body.
I think with sleep apnea the duration of the apnea can be as much as 30 seconds to a minute at a time.
Almost all sufferers of Sleep Apnea are also Snorers, makes sense as people who snore have problems with their airway.
Again I don't know exact figures but I remember reading that a large percentage of Sleep Apnea sufferers are overweight, and generally not very fit/ poor health.
Now with Eric's description, if a person like this goes through an Apnea workout every night, no wonder they feel so tired ?
I get tired from Apnea training and I'm pretty fit