Wednesday, July 28, 2004

Medical Reasoning:
Insight into the Mind of the Physician

Courtesy of Downstate Medical Center
The author, all wired up and preparing for, he hoped, some rest.
The New York Times today has an article about sleep apnea.  It actually is an article written by a journalist, detailing the problem he had with hypersomnia, and his experience getting a clinic polysomnogram (sleep study.) 

Published: July 27, 2004

I haven't slept well for years.  If I set an alarm for 6:30 a.m., my eyes open at 5, and I try to doze to the radio. I drink four cups of coffee a day. I don't think I have ever fallen asleep at the wheel, but I often pull over nodding off.

Cripes, man, if you have to pull over because you are drowsy, you need to see a sleep specialist, like Right Now!

I used to work nights, which first threw my rhythm off. But I liked having days with my daughters and not being a creature of habit, perhaps because my father, who slept nine hours a night, was someone you could set a clock by.

Lately, though, it had gotten ridiculous. So when the new sleep lab at Downstate Medical Center in Brooklyn offered to let me bring my pillow over for a test snooze, I jumped. [...]

In the remainder of the article, he discusses the seriousness of the problem of obstructive sleep apnea, and tells what he went through to get the diagnosis.  He promises to tell about the treatment in a future article.  In my opinion, he should have emphasized the dangerousness of driving while drowsy, but then, he's not a public health specialist. 

I've written about sleep disorders here before, at the Corpus Callosum, often to illustrate points about physiology or medical theory.  Use the search function in the sidebar if your are interested.  Today, I'll use the opportunity to show a connection between sleep disorders and post-stroke mortality, and make a point about interpretation of medical literature. 

From Medscape News (free registration required):

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LONDON (Reuters) Jul 27 - The occurrence of sleep apnea, especially obstructive sleep apnea, in stroke patients is associated with an increased risk of stroke-related mortality, Spanish researchers report in the European Respiratory Journal.

"It's the first time the link between apnea and stroke has been shown to affect mortality," said Dr Olga Parra at Barcelona University Hospital.

Dr. Parra and her colleagues monitored the breathing of 161 stroke patients shortly after they were admitted to hospital and calculated an apnea index for each one.

During the 30-month study, 22 patients died. The higher the patient's apnea score, the greater the risk of dying from stroke, the researchers found.

"This Spanish study represents a milestone in our understanding of the potential role of sleep apnea in stroke patients," Dr. Ludger Grote, of the Sahlgrenska Hospital in Sweden, writes in a commentary in the journal.

"Its results could have considerable implications for the future management of stroke," he adds.

Dr. Parra and her team have now launched a study in several centers in Spain to see if treating sleep apnea with continuous positive airway pressure ventilation could cut the death rate from stroke. The results of that study are expected in about five years.

Eur Respir J 2004.

The authors show a correlation between the severity of sleep apnea, and the risk of death after a stroke.  We know already that untreated sleep apnea increases the risk of death, from a variety of causes.  One might be tempted to conclude, then, that treatment of the sleep apnea would decrease the risk of death after stroke, in patients with sleep apnea.  However, the authors go on to say that they are doing a study to see if treating the apnea can reduce the mortality risk.  Why bother to do a study, especially if it is going to take five years to do the study? Is it not obvious what the result will be?

Remember: Observations are gold; hypotheses, silver; and conclusions, bronze.  Nothing in human physiology is even simple.  As tempting as it may be to jump to the conclusion that the study is not necessary, because the outcome is obvious, it is not wise to jump to that conclusion when lives are at stake. 

A good example of this is seen in the standard practice of treating strep throat with penicillin.  In most cases, strep throat goes away on its own, and the treatment only shortens the duration of illness by a short time.  However, we know that untreated strep throat carries an increased risk of rheumatic fever.  We also know that many antibiotics can kill the strep.  Therefore, it is tempting to conclude that you could use any antibiotic that is known to kill the bacteria, and that would reduce the risk of rheumatic fever.

The thing is, most of the studies done on the use of antibiotics to reduce the risk, used penicillin as the treatment.  Yes, you could use something else, and it probably would work.  But, it has not been observed directly that it would in fact reduce the risk.  Since the observation always outweighs the hypothesis or conclusion, it is most wise to stick with what is known by direct observation. 

It happens fairly often in a doctor's office that a patient will come in with a printout from some web site (such as this one, I know) and propose some kind of treatment based upon what he or she has concluded from the article.  If the doctor has the time (hah!), she or he might explain the reason why the treatment is not the best course of action: it has not been shown directly to produce the desired outcome.  Sometimes, the theory is all you have to go on, in which case it may be reasonable to proceed.  Usually, though, it is not wise to do so.  There all all kinds of risks involved in basing treatment decisions on untested ideas.

(Note: The Rest of the Story/Corpus Callosum has moved. Visit the new site here.)
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