The schedule of a motorcoach driver can be erratic, and getting enough sleep a challenge.

And even on nights (or days) when drivers do get a full cycle of sleep, they may still wake up feeling fatigued.

An inconsistent sleep schedule and possibly even a sleep disorder could be affecting a driver more than he or she realizes.

According to Dr. Carol Ash, medical director of the Sleep for Life program in Hillsborough, N.J., these problems can affect driving in a couple different ways.

First is the issue of sleep debt, which is a consistently inadequate amount of sleep. "Sleep debt is dangerous," says Dr. Ash. "It impairs focus, concentration and judgment."

If you've gone 18 consecutive hours without sleeping, the affect on your brain is the same as if you were legally drunk.

"Once sleep debt reaches a certain severity," she says, "micro-sleeps --tiny periods of sleep -- intrude into wakefulness."

Obviously, a driver isn't safe behind the wheel if these micro-sleeps are forcing him or her to unknowingly doze off.

The second concern is that an irregular sleep schedule can mess up an individual's circadian rhythm, the normal rhythm of your body. Humans are wired to sleep when it's dark and be awake when it's light. So, if your circadian rhythm is disturbed, you're going to feel grumpy, groggy and gloomy even if you are getting five or six hours of sleep.

Aside from your irregular schedule is the matter of sleep disorders.

According to the National Sleep Foundation, 28 percent of commercial drivers suffer from moderate to severe sleep apnea. Apnea occurs when an individuals airway closes off during sleep and prevents a person from taking in the oxygen needed while asleep. It can lead to a heart attack, a stroke, diabetes and more.

How can an individual determine whether he or she might suffer from sleep apnea?

According to Dr. Ash, some common signs are: snoring; waking with a headache and dry mouth; acid reflux; frequent nighttime urination, and a neck size of more than 17 inches in men or 15 inches in women. If you suffer from these symptoms, check with your doctor.

"Sometimes obstructive sleep apnea is more prevalent in obese people and can be treated by weight loss," states Ash, "but this is a condition that affects people of all body types. The gold standard of care is a Continuous Positive Airway Pressure unit, a medical device that gently blows air into the airway to keep it open during sleep."

Whether an individual is sleep deprived, suffering from apnea or both, if a person finds she or he is getting drowsy while driving, there is only one option: Sleep. Caffeine, loud music or cool air from an outside window aren't real remedies.

Dr. Ash says that if you can't pull over and sleep for a full cycle, aim for a 20-minute nap. Anything longer will actually put you into a deeper sleep phase, causing you to wake up feeling groggy.

Try to determine how many hours of sleep you require and do your best to get it. Not an easy task, of course. And see your doctor if you suspect you have a sleep disorder.