Until I read your question, I was not familiar with "shift work disorder." A bit of quick research informs me that "shift work sleep disorder" is a sleep disorder that affects those who often work at night or frequently rotate shifts, such that their schedules run counter to the body's natural Circadian rhythm, resulting in their having difficulty adjusting to their sleep and work schedules. It resutls quite often in either insomnia or excessive sleepiness.
There may perhaps be other attorneys on this site who are more familiar with this disorder, but to me it is difficult to classify it as a disability. I suppose that even if this were a possible disability, that an employer would experience hardship if it had to accommodate employees who spend their time sleeping on the job, which would potentially impair your ability to use the Americans with Disabilities Act as a protector.
You should consult with a local attorney, but if he or she doesn't show up for your appointment, I guess that he or she may suffer from showing up on time for an appointment disorder.
Good luck to you.
Michael S. Haber is a New York attorney. As such, his responses to posted inquiries, such as the one above, are limited to his understanding of law in the jurisdiction in which he practices and not to any other jurisdiction. In addition, no response to any posted inquiry should be deemed to constitute legal advice, nor to constitute the existence of an attorney/client or other contractual or fiduciary relationship, inasmuch as legal advice can only be provided in circumstances in which the attorney is able to ask questions of the person seeking legal advice and to thus gather appropriate information.