Sleep apnea is diagnosed with a sleep study that examines breathing patterns during sleep. There are two basic kinds of sleep studies in widespread use: studies done in an individual’s own bed at home and those done in a sleep laboratory.
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What Is a Home Sleep Study?
Individuals with a high likelihood of having sleep apnea can be tested at home, especially if he does not have significant medical conditions involving the heart or lungs. The patient puts the testing equipment on himself before going to sleep. This equipment monitors breathing patterns, oxygen levels and heart rhythms.
What Are Laboratory Sleep Studies?
An in-laboratory sleep study (also called polysomnogram) is a more-detailed test that evaluates breathing patterns, oxygen levels and heart rhythms more closely and also monitors brain-wave activity (modified electroencephalogram), eye movements (electrooculogram) and leg movements. A polysomnogram is a test for sleep apnea and some other sleep disorders, such as periodic limb movement disorder.
What Are the Pros and Cons of a Home Sleep Study?
Home sleep studies are generally cheaper than in-laboratory studies. They can be more comfortable because an individual has to wear fewer monitors and is able to sleep in their own bed. The drawbacks include the fact that they provide less information, are not able to evaluate sleep disorders other than sleep apnea and are not ideal for individuals with major medical conditions affecting the heart or lungs. After a home sleep study, an in-laboratory study may need to be performed if the home sleep study does not diagnose sleep apnea, but the physician believes the patient is at high risk of having sleep apnea.
Also, if a patient has sleep apnea during the first half of an in-laboratory sleep study, they can start treatment (positive airway pressure therapy) that same night. This takes advantage of the fact that a patient is already in the sleep laboratory to determine the optimal settings to use at home.
What About Other Sleep Tests?
Measurement of oxygen levels in the bloodstream, called oximetry, is not a sufficient test for sleep apnea by itself because many patients with obstructive and central sleep apnea can have normal oxygen levels. Multiple sleep latency testing is a daytime nap test, and it evaluates the degree of sleepiness and can be essential in the diagnosis of narcolepsy, a different type of sleep disorder. Actigraphy involves wearing a wristwatch-style device that measures cycles of wakefulness versus sleep that can be relevant for the evaluation of disorders of daily (circadian) rhythms.
What About Blood Tests for Sleep Apnea?
There are no blood tests for sleep apnea, specifically, but blood tests can be part of the evaluation of patients with symptoms of sleep apnea or other sleep disorders. For example, hypothyroidism often leads to low energy levels, fatigue and sleepiness that can mimic sleep apnea symptoms. Therefore, individuals with these symptoms should have a blood test to assess levels of thyroid-stimulating hormone.
Also, restless legs syndrome is a disorder of leg discomfort, particularly in the evenings. It can contribute to difficulty falling asleep or remaining asleep during the night, and it can start or become worse in the setting of low iron stores in the body. Therefore, a patient with symptoms of restless legs syndrome should have a blood test to assess ferritin levels.