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Sleep Disorders

Absence of Slow Wave Sleep

02/24/2009

Question:

I am a 34 year old average weight female with no major health problems. However, I experience an extreme lack of energy, painful and tender muscles, lack of focus and feeling of being in a fog during the day. My PCP referred me to a sleep doctor and I had a sleep study done. It came back perfectly normal, with the exception that my "sleep architecture indicates an absence of slow wave sleep." The study indicates 0 min of slow wave sleep. I have been assured that this is nothing to worry about, that I am indeed getting slow wave sleep but it just isn`t deep enough to technically qualify as such on the report due to my "advanced" age of 34.

Is it true that as we age that we are not expected to get deep enough sleep to show up on a sleep study? If that is the case why don`t they have different methods of qualifying sleep as we get older? If my sleep study was truly normal, why was this called out in the summary?

Thanks so much!

Answer:

Slow wave sleep (SWS) is commonly referred to as “deep sleep” and also know as “delta wave sleep.” In one respect, it can be considered one of many measures of the quality of sleep. You are correct in stating that SWS decreases with aging, however, this occurs later in life than the thirties (usually in the 50-60 age group and older). In the elderly, wave forms similar to slow waves are found, but they are too low in amplitude (height of the wave forms) to be counted as slow waves using the existing criteria. There is some debate about the meaning of the waves and whether or not we should use different scoring criteria in the elderly. Again, this unlikely to be the case in your age group.

The explanation for not having SWS on your sleep study is probably not your age. Sleep in the sleep lab, as surprising as they may sound, is frequently not an accurate reflection of the individual’s sleep at home. In the sleep lab, the person is connected to numerous wires and is sleeping in a foreign environment. It is common for the sleep architecture to be disrupted during sleep testing.

Sleep studies are mostly performed to rule in or out known intrinsic sleep disorders that can cause daytime symptoms such as sleepiness. There are many indications for a sleep study, but some of the more common disorders include the sleep apnea syndromes and periodic limb movement of sleep. Evaluation of the sleep architecture is only one part of the general clinical sleep study. Abnormalities in sleep architecture are often attributed to the sleep lab environment if there is no underlying intrinsic sleep disorder.

However, in some instances, thorough evaluation by a sleep physician can suggest other explanation for reduced SWS. Medications, particularly sleep aids and antidepressants, may be associated with reduced SWS. In addition, conditions such as depression and fibromyalgia may also be associated with consistent sleep architecture changes.

I recommend you discuss your sleep study results with your sleep physician. After reviewing your history and your sleep study, they should be able to provide with you a more specific answer to your question.

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Response by:

Rami N Khayat, MD Rami N Khayat, MD
Clinical Assistant Professor of Pulmonary, Allergy, Critical Care & Sleep
College of Medicine
The Ohio State University