Sleep apnea, insomnia, and other abnormal sleep behaviors may result in excessive daytime sleepiness and an inability to maintain the alertness necessary for safety while operating machinery, driving or flying. 
Cognitive function and neuromuscular coordination may both be affected by a sleep disorder and/or the treatment modalities used.
Persons with a sleep disorder may have more than the usual difficulty in adjusting to the circadian rhythm disruption, which occurs with travel across time zones.
This would present an additional hazard to a flier who may deploy several time zones away and would still be expected to perform flying duties.
In some vocations, sleep studies are required in order to receive certain types of medical certification. The Sleep Medicine Center offers 24 hour testing for employees who are involved in high-risk vocations and need medical certification. Call our office for more information on studies for medical certification at 314-362-4342.