I just called the FAA regarding Sleep Apnea which I have. I am furloughed and thought I'd jump threw the hoops before I get recalled. Last Summer I did a sleep study and confirmed I do have sleep apnea. I was issued a CPAP and the Sleep and Lung clinic monitored me threw a wireless device on the CPAP machine itself. My numbers are back in the normal range. I have to supply the FAA with all the paperwork of the Dr's findings from the sleep study plus the records of them monitoring me. They also said that when I got to my doctor for my 1st class physical, present these items to him and he can get an over the phone temporary approval to issue me the 1st class.
If you are a person that gets sleepy during the day, which I'm not, then there is that 'Daytime wakeful sleepiness' test but not everyone has to do it. All depends on the results of the sleep study and there after.
Hope this helps.