She replied, “There’s a constellation of symptoms, starting with unrestorative sleep no matter how long you sleep. Even if you try to sleep more on weekends, you still wake up feeling unrefreshed. The fractured sleep results in feeling like you’ve stayed up all night.”

Then she added a list of other clues. Perhaps most telling: You are sleepy during the day, especially when you’re sedentary. Take notice if you fall asleep within 10 minutes at a movie, play or concert or when watching TV. You get up four or more times a night to urinate (men, it may not be your prostate!). You wake up in the morning with a very dry mouth or a headache. You’re moody, irritable and have difficulty concentrating. Your reaction time and speed at performing tasks slows as if you are five years older than you really are.

Those who experience even a few of such symptoms would be wise to bring them to their doctors’ attention, Dr. Veasey said.

And if you’d rather not base your suspicions on symptoms alone, you might invite a close friend to share a room with you for a night or two and ask in the morning if the friend heard or was awakened by your snoring and noticed whether your noisy inspiration of air followed a seemingly prolonged stoppage of breathing. The snoring doesn’t have to be loud to be a symptom of sleep apnea, but it’s likely to be irregular and interspersed with quiet pauses.

A proper diagnosis can be a problem for the millions of Americans who lack easy access to a sleep lab, often located at major medical centers, or don’t have insurance coverage for a needed sleep study.

There is also the option of a home-based test, which costs a third to a half less than a sleep lab study. It uses a device without electrodes that records breathing efforts, airflow and blood oxygen levels during sleep.

Sleep apnea can be effectively treated with a nighttime device called CPAP, for continuous positive airway pressure, a machine that provides constant positive pressure when the sleeper breathes in and out. It uses a mask that must be properly applied to form a tight seal around the nose and mouth.