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Monday, November 24, 2014
Sleep Study Results. I`m confused.
I`m a 46 yr old female. Had a PSG done with the use of Lorazepam. I`m confused. I`m told I do not have OBSA/CSA but yet had 22.7 arousals and 3.4 awakenings per hr of sleep. Apnea/hypopnea index normal at 0.9 events per hr. Oxygen mean saturation 99%. No perodic limb movement disorder, restless legs, etc...My question is what is causing these arousals. Medication at time of test - 10mg citalopram.
You must have done a lot of research regarding your sleep situation and test results. I am glad you decided to write to us with your question. What is listed below is probably not going to be a surprise to you, but may provide some reassurance.
Possible reasons for arousals from sleep include:
Sleep Apnea: The Apnea-Hypopnea Index (AHI), the primary parameter that is evaluated for the diagnosis of sleep apnea, can be quite variable from night to night. A single night sleep study may not determine the AHI accurately in up to 15% of sleep studies. And some people, with significant disease, may have their sleep apnea underestimated and thus missed during one night and yet have significant sleep apnea on a second night in the lab. When someone has significant symptoms, but no sleep apnea on one test, we sometimes ask them to repeat the test, to be sure that there is no sleep apnea. This is important because sleep apnea is the most common cause of arousals from sleep.
Upper Airway Resistance Syndrome: The resistance of the upper airways can be high enough to cause arousals from sleep. This resistance may not show up as apneas (no air flow) or hypopneas (limited air flow), by usual detection methods in the sleep lab. This kind of situation, known as Upper Airway Resistance Syndrome (UARS), needs special tests to detect it. These tests are not common and they involve the use of an esophageal probe, which is a thin wire that the patient needs to swallow and keep in place during the test. You can imagine why this type of test is not in wide use. However, if UARS is clinically suspected, a patient may benefit from the same treatment options that are available for sleep apnea.
Medications and Substances: There are many medications and substances that can cause a high number of arousals from sleep. The most common are caffeine, nicotine, and alcohol. In those cases, a simple trial of stopping these substances may prove helpful (once over the acute withdrawal phase) in restoring sleep continuity. Although citalopram and lorazepam do not cause arousals during sleep, they do however change the structure of sleep. Citalopram decreases Rapid Eye Movement sleep and lorazepam increases slow wave sleep. Both situations may result in an under-estimation of the severity of sleep apnea if one has it.
Periodic Limb Movement Disorder: You mention that this was not evident from your sleep study.
Medical conditions: There are multiple chronic medical conditions that can cause disturbances during sleep. Some of these include chronic pain syndromes, anxiety, heart burn (or gastroesophageal reflux = GERD) and asthma.
But what does it mean to have 22.7 arousals and 3.4 awakenings per hour of sleep? In the sleep lab, probably not much! It really depends of the person’s symptoms. When you are in the sleep lab, as you know, you are connected to about 20 wires and are asked to sleep in an unusual bed, and away from familiar surroundings. In those situations, frequent arousals are common and are part of the so-called “first night effect” of sleeping in the sleep lab. If you don’t have any symptoms to indicate that your sleep is interrupted or not restorative on regular basis, then I suggest that you not worry about the test results. Otherwise, you need to have a Sleep Specialist discuss your medical history with you, do a thorough examination, and obtain appropriate tests to rule out any problems with your sleep continuity.
The American Academy of Sleep Medicine has information online about Sleep Centers across the country so you can locate one near you. Please don’t hesitate to let us know of any progress in your story.
Best of luck. May you have restful sleep.
Ziad Shaman, MD
Assistant Professor of Medicine
School of Medicine
Case Western Reserve University