obstructive sleep apnea/hypopnea syndrome
"I have Sleep Apnea and use CPAP but unfortunately the CPAP doesn't completely resolve the exhaustion.  I take 200mg Provigil once a day and it has given me my life back.  I was in danger of losing my job because the exhaustion caused me not to be able to focus or produce.  Once on the Provigil, my boss says he has been blown away by my performance.  No side effects whatsoever."