Can an employee who falls asleep at work be allowed to continue to work?

Snoeck cites Overton v. Reilly (7th Cir. 1992) 977 F.2d 1190, 1195 for the proposition that an employee whose "sleepiness is a function of his disability" must be permitted to work if "he can still perform the essential functions of his job." Reviewing a grant of summary judgment, the appellate court there concluded questions of fact existed as to whether a terminated employee, who had a mental disability, still could perform the essential functions of his job when there was evidence he got his work done despite falling asleep at his desk at times "when he had nothing to do[, ] and his medication made him drowsy." (Id. at pp. 1191, 1195.)