If you find yourself falling asleep or feeling excessively tired and drowsy during the day, you may have a sleeping disorder. These symptoms alone won’t tell you which disorder you have, though. Daytime sleepiness is a shared symptom of both sleep apnea and narcolepsy, for example. Read on for more details about how narcolepsy and sleep apnea differ, and what tests can help determine which one you might have.
What is sleep apnea?
Sleep apnea is a condition that causes periods of apnea, or the temporary cessation of breathing, while you are asleep. The two main forms of sleep apnea are obstructive sleep apnea and central sleep apnea.
With obstructive sleep apnea, breathing stoppage occurs when relaxed tissues physically block your airways. According to the American Sleep Association, obstructive sleep apnea is common in people who are overweight or obese. Excess weight around the neck and throat places increased pressure around the airways, which can block airflow.
Withcentral sleep apnea, breathing stoppage results from disrupted brain signalling that impairs the normal function of the muscles involved with breathing.
What is narcolepsy?
Narcolepsy is a sleep disorder that interferes with your brain’s ability to control normal sleep and wake cycles. According to the National Institute of Neurological Disorders and Stroke, narcolepsy can cause people to fall asleep during activities like talking, eating, or driving.
“Narcolepsy, which has different subtypes, is a central disorder of hypersomnolence. It is a condition produced by alterations in the neurochemistry of the sleep-wake circuit of the brain,” Ian Katznelson, MD, Neurology and Sleep Specialist at Northwestern Medicine Lake Forest Hospital, tells WebMD Connect to Care.
Cataplexy, or sudden muscle weakness while you're awake that makes you unable to move, is also a characteristic symptom of narcolepsy. Cataplexy due to narcolepsy may make it seem that you are having a seizure, but patients are fully conscious when these spells of muscle weakness occur.
How do doctors determine which condition you have?
The first step in the diagnosis of a sleeping disorder is an examination with your doctor, who will review your symptoms and medical history while ruling out other neurological problems. Cataplexy, for instance, is narcolepsy’s most unique symptom which occurs in virtually no other disorders.
A multiple sleep latency test can be used to help diagnose narcolepsy. This test measures how quickly you fall asleep and how fast you enter the deep stage of sleep called rapid eye movement (REM) sleep. According to the National Institute of Neurological Disorders and Stroke, people with narcolepsy enter REM sleep abnormally early—typically within 15 minutes of falling asleep.
Polysomnography, or a sleep study, is the current standard for diagnosing sleep disorders like sleep apnea. This in-lab diagnostic testing measures your blood oxygen levels, breathing, and brain and muscle activity during sleep to determine if your airflow is being blocked. There are also simplified versions of this test available via telemedicine for at-home sleep apnea testing.
“Though they are different entities, it is not uncommon for sleep apnea and narcolepsy to occur together, making the management of such patients potentially quite challenging,” Katznelson adds.
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