Once you have been given a tentative diagnosis of sleep apnea or a similar sleep/breathing disorder, an all-night sleep test should be arranged. Proper testing for sleep disorders is important because several sleep disorders have superficial similarities and might be confused with sleep apnea or be incorrectly diagnosed if testing is not done properly. An incorrect diagnosis, leading to incorrect treatment, can be a serious error. For example, medications that are often prescribed for narcolepsy or insomnia can actually worsen sleep apnea, so a correct diagnosis is very important.

Narcolepsy is a sleep disorder in which people have irresistible “sleep attacks” at inappropriate times, somewhat as in sleep apnea. However, narcolepsy is a distinct neurologic disorder with its own characteristic symptoms (cataplexy, sleep paralysis, and hypnagogic hallucinations) not found in sleep apnea.

Insomnia is sometimes confused with sleep apnea. Insomnia has numerous causes, and only a few people who have insomnia also have sleep apnea.

Two other sleep disorders sometimes occur alone or along with sleep apnea. These are periodic limb movement in sleep (PLMS, also called periodic leg movement disorder, PLMD, or nocturnal myoclonus) and restless leg syndrome (RLS). Again, appropriate testing by an experienced sleep disorders specialist will avoid confusing one sleep disorder with another.

An overnight sleep test will:

1. Confirm whether you actually have sleep apnea or another form of sleep-disordered breathing
2. Determine the type of sleep/breathing disorder, which must be known in order to select the appropriate treatment
3. Rule out other sleep disorders