Went to the Lecture in DC in March, the speaker was Dr. David M. Rapoport, founder and director of the New York University Sleep Disorders Center and Director of the NYU Sleep Medicine Program. The Lecture was entitled "Catching Our Breath: Reflections on Diagnosis and Treatment of Obstructive Sleep Apnea."

There were a number of very interesting subjects in this lecture, as the lecture was approximately 1.5 hours, I won't try to cover all the subjects, but cover some of the main points.

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Obstructive Sleep Disorder Breathing is the spectrum from complete obstruction to mild obstruction. It is an intermittant functional obstruction, meaning that most apneacs when they are awake do not have a problem with breathing and only comes out during sleep and it is not entirely anatomic. OSDB is defined by repetitive events combined with consequences, such as daytime sleepiness.

The sleep cycle in an apneac, is basically sleep induces a lack of muscle tone in the upper airway, the lack of muscle tone results in an obstruction, the obstruction results in a variety of things including chemical stimuli the asphyxia or choking that occurs and the response which is the arousal itself that restores the muscle tone and now allows you to go back to sleep. The AHI or RDI is the number of cycles that you go through in an hour.

But, in fact, the consequenses are not straight forward results of AHI/RDI. Part of it is individual susceptability.

The traditional way to measure this is with a sleep study (PSG). In severe form, OSDB is very easy to recognize.

In the 1970s it was thought that OSA was an extremely RARE disease. It was thought that failure of the right side of the heart was a primary indicator of OSA.

The landmark study by Terry Young in 1993 funded by the NIH showed that in a non-patient population, there were an astronomical number of people had what we were calling the cutpoint for the disease, 5 events per hour. 24% of men, and 9% of women. If you went with a more restrictive number of events 15, and they had to have sleepiness, you have 4% of men and 2% of women. They also showed that there was only a slow increase in the severity.

The other important study is the Sleep Health Study of 1999 (also by the NIH). There were about 6500 patients included in this study. In this study they found that 1/5 of the population studied had 30 events per hour, 2/5 had over 15 per hour and the overall average was 11 per hour.

So we moved from thinking it was fairly rare, to realizing that it is fairly common.

Statistic 50% of men snore, while only 30% of women do.

How we detect the sleep disordered breathing has a huge impact on what you see. Is there an event, and does it matter? It is not clear that finding an obstruction matters unless there are consequences.

How you measure it is going to determine what you see. Some detectors are very sensitive, some detectors are less sensitive. And are there consequences.

If you take events that are reasonably similar in different people, some produce desaturation, others produce arousals, some produce both, and there are no real solid relationship between these things.

In a study that used a sensor that measures temperature only, versus a sensor that measures pressure, 60% of events were missed by one or the other sensor.

One of the big problems with the literature that is published today is this very fact.

You can NOT compare between labs unless you know they are doing the same thing. But if you see more than 5 obstructive apneas per hour that is probably normal, but if you are less than 5 that doesn't guarantee that you are normal as there might be a lot of other events. You might have up to 20 partial blockages and still be normal. Nobody really knows. The bottom line is that over 20 events of any kind is probably abnormal. Below 10 by my count is probably normal. Other people that use less sensitive sensors say you have to be less than 1 or 2. In the gray zone there are some people and we don't know. I can show you 2 people with the same count, 1 with symptoms and 1 without. There is something else missing. We still don't know what to measure. Another possibility is that the number of stress events is only a risk factor. How you respond to it will determine if you have disease. It is highly likely that some degree of the latter will be the case about apnea.

What are some of the consequences of sleep disruption.

It was shown that that it slows reaction time.
It causes perseveration.
Lapses in Data Collection.
Decision making is impaired.
Memory is affected.

This is very hard to measure but there is pretty good consensus and most of us feel that this intuitively that this makes sense.

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It can be shown that if you count the number of events against the sleep/heart/health data that people report that they are more sleepy.

Sleep Disordered Breathing Events cause very dramatic changes in the sympathetic nervous system. At the moment of arrousal it has been measured that blood pressure increases, and only lasts a few seconds. What if this happened over and over? A experiment in Canada by Elliot Phillipson were he gave dogs severe sleep apnea through artificial means and what he showed was their blood pressure went up during sleeping. The question was asked what if it is just arrousals? The same thing happened. However, the ones with the apnea that were looked at during the day had elevated pressure where the ones with just the arrousals did not.

How do we put this all together into a chronic story? Well if you say Sleep Disorder Breathing has the 2 major effects of lowering your oxygen and waking you up, stimulates you into stress, that stress and several other things causes transient blood pressure rises, those transient things if repeated enough may cause chronic blood pressure rises, chronic blood pressure we know is bad for you and causes cardiovascular morbidity that is a nice way to tie it all together. Probably not this simple, and it needs to be proven, because many simple things we assumed have turned out not to be true.

So what data do we have? If you have a higher level of apnea, you have about one and a half times chance of having hypertension compared to people with lower level of apnea. Looks like associated not cause. There is very early data showing that treating it changes it.

There is a fascinating paper that came out a few weeks ago in the New England Journal that talks about the time that people die. There is a well known observation that people have a tendancy to die in the 6am - 12noon period. The sleep apnea patients died 6 hours earlier in the 12midnight - 6am period. There is a difference in the pattern, this is not conclusive but it is very suggestive that even if sleep apnea doesn't cause anything, that it picks out people that are susceptable, much as any other stress might, and therefore might be worth addressing even in those people that don't have symptoms.

Let me sumarize what I have said so far.

Sleep apnea has consequences. Those consequences include:

excessive sleepiness, but not in everyone
decrease quality of life
impaired memory
hypertension, possible heart attacks, and possible strokes
and death seems to be increased in severe sleep apnea
increased risk of diabetes
another fascinating but also early report suggests that it also might cause increased appetite.

What are the treatments?

If you are overweight it helps to lose the weight, and it doesn't always work, but it works in enough people that it is worth pursuing.

Correcting abnormal anatomy is great when we find it, but quite often we don't find it.

Upper airway congestion, you treat it.

The mainstay today though is CPAP. It works incredibly well. The problem is that patients don't necessarily use it.

There are surgeries out there, and they only work in a fraction of patients and only have a success rate of 25% and it tends to only work in people in the milder end of the spectrum.

Dental devices, that pull the jaw forward, again, logical, seems like a great idea, should have worked better than it did, does work in enough patients that we are still doing it, but doesn't work quite predictably enough to be a mainstay treatment, certainly not of severe disease.

Take home messages for 2005:

Sleep Apnea is a extremely common disease rivals diabetes and hypertension

Consequences do exist, and probably exist even for moderate sleep disorder breathing

Diagnostic tools are cumbersome, and they are really not as helpful as tradition suggests. We need new tools, and more importantly we need to prove the new approaches which are not just tools, but the way they are used, that those new approaches actually are valid and they produce useful results that will help patients and help doctors make decisions about patients.

Treatment IS effective! It is Primitive, but it does work.

Patients have taught us more than we acknowledge. Many of the improvements in CPAP have come the same way, they tell you what works.