Diagnosing sleep disorders is, at best, an imprecise process—first, because scientists are still learning about the physiology of sleep and, second, because patients are unable to provide clues about problems that occur while they’re sleeping. However, there are two standard tests that help doctors identify sleep disorders: polysomnography and the Multiple Sleep Latency Test. Your doctor may also want you to undergo tests that analyze your biochemical characteristics, such as a blood test called a radioimmunoassay (RIA), which measures levels of melatonin. If your physician suspects you have obstructive sleep apnea, you may take a breathing test, during which technicians use an oximeter to measure your breathing patterns, blood oxygen levels, and respiration rates as you sleep.
• Polysomnography—This test monitors bodily functions, including electrical activity of the brain, eye movement, muscle activity, heart rate, air flow, and blood oxygen levels, during sleep. This test is often used to diagnose sleep apnea, narcolepsy, restless legs syndrome (RLS), and periodic limb movements in sleep (PLMS), but may be employed to test for other sleep disorders.
• Multiple Sleep Latency Test (MSLT)—The test measures how long it takes a person to fall asleep at any point during the day as drowsiness occurs. Generally, people without sleep disorders fall asleep in ten to 20 minutes; those who fall asleep in less than five minutes are categorized as experiencing sleep deprivation and a sleep disorder of some type. This test is typically used to diagnose sleep-onset insomnia, sleep apnea, and narcolepsy.
