Wednesday, September 21, 2005

Sleep Apnea Updates

There are three: one from WebMD; the other two, from the WebMD professional companion site, Medscape (free reg. req.).  I used to post fairly often on medical topics that show that illness are often much more complex processes that they appear to be.  Today, I stick to more practical "clinical pearl" matters.  
Treatment for Sleep Apnea May Ease Depression
Symptoms of Depression Often Overlap With Obstructive Sleep Apnea; CPAP May Help

By Miranda Hitti
WebMD Medical News    
Reviewed By Brunilda  Nazario, MD
on Monday, September 12, 2005

Sept. 12, 2005 -- People with obstructive sleep apnea often show signs of depression, and treatment that prevents snoring and breathing disruptions may help, new research shows.

According to the national sleep foundation, obstructive sleep apnea is a disorder in which breathing is briefly and repeatedly interrupted during sleep. It occurs because muscles in the throat are not able to keep the airway open.

The treatment called CPAP (continuous positive airway pressure) is a device that helps people with obstructive sleep apnea breathe more easily during sleep.

At a Florida sleep center, 50 patients were recently asked to use CPAP for four to six weeks. The patients' depression symptoms improved during that time, according to a study in Chest.

The researchers' recommendations:

    * Screen people with depression symptoms for obstructive sleep apnea.
    * Screen people with obstructive sleep apnea for depression. [...]
Obstructive Sleep Apnea Associated With Early Signs of Atherosclerosis

By Will Boggs, MD

NEW YORK (Reuters Health) Sept 02 - Otherwise healthy middle-aged patients with obstructive sleep apnea (OSA) show early signs of atherosclerosis, according to a report from Brazil. "Our findings support the hypothesis of a direct link between obstructive sleep apnea and cardiovascular diseases," Dr. Luciano F. Drager told Reuters Health.

Dr. Drager and associates at the University of Sao Paolo measured early atherosclerosis indicators -- that is, pulse wave velocity (PWV), carotid diameter, and intima-media thickness (IMT) -- in 30 patients with untreated OSA and 12 matched healthy volunteers. None of the participants had previous evidence of cardiovascular disease.

All three indicators of early atherosclerosis showed a trend toward direct correlation with the severity of OSA, the investigators report in the September 1st issue of the American Journal of Respiratory and Critical Care Medicine. [...]

Long-Term Effects of Nasal Continuous Positive Airway Pressure Therapy on Cardiovascular Outcomes in Sleep Apnea Syndrome
Liam S. Doherty, MD; John L. Kiely, MD; Valerie Swan, RgN; Walter T. McNicholas, MD, FCCP

Background: Obstructive sleep apnea syndrome (OSAS) has been associated with increased morbidity and mortality, principally from cardiovascular disease, but the impact of nasal continuous positive airway pressure (CPAP) therapy is unclear.
Methods: We performed a long-term follow-up study of 168 patients with OSAS who had begun receiving CPAP therapy at least 5 years previously, most of whom had been prospectively followed up, having been the subject of an earlier report on cardiovascular risk factors in OSAS patients. The average follow-up period was 7.5 years. We compared the cardiovascular outcomes of those patients who were intolerant of CPAP (untreated group, 61 patients) with those continuing CPAP therapy (107 patients).
Results: CPAP-treated patients had a higher median apnea-hypopnea index score than the untreated group (48.3 [interquartile range (IQR), 33.6 to 66.4] vs 36.7 [IQR, 27.4 to 55], respectively; p = 0.02), but age, body mass index, and time since diagnosis were similar. Deaths from cardiovascular disease were more common in the untreated group than in the CPAP-treated group during follow-up (14.8% vs 1.9%, respectively; p = 0.009 [log rank test]), but no significant differences were found in the development of new cases of hypertension, cardiac disorder, or stroke. Total cardiovascular events ( ie , death and new cardiovascular disease combined) were more common in the untreated group than in the CPAP-treated group (31% vs 18%, respectively; p < 0.05).
Conclusions: The data support a protective effect of CPAP therapy against death from cardiovascular disease in patients with OSAS. [...]

The take-home points seem fairly straightforward.  

There is overlap in the symptoms presented by patients with OSA, and in those presented by patients with depression.  Often they coexist.  So from the doctor's perspective,  if you see one, you should look for the other.  From the patient's perspective, if you are treated for one and do not get as much improvement as you think you should get, ask about the other.   I would add that in a secondary or tertiary care setting, these correlations are going to be stronger than in a primary care setting.  

OSA is associated with accelerated atherosclerosis.  So it might be worth treating, even if the cardinal symptom of daytime sleepiness is not very bad.  Of course, you might not want to do that unless you have some evidence that the treatment actually does some good.  To expand on that point: If a study shows an association between factor A and effect B, and there are good theoretical reasons to believe that factor A plausibly could be a cause of effect B, then it is tempting to try to correct factor A in an effort to prevent effect B.  But, alas, that is not always the case.  

That is where the third study comes in.  Careful readers will see that the second and third studies presented here do not provide proof that it is worthwhile to treat OSA patients who have minimal symptoms.  But together, the two studies are highly suggestive.  Assessment and treatment of OSA can be costly, but the third study indicates that the potential benefits are large.  

Obstructive sleep apnea, at first glance, appears to be a fairly simple problem.  Something in the airway constricts under conditions of reduced pressure, caused by inspiration.  That blocks air flow.  Use a machine to increase the pressure, and the problem is solved.  It turns out, though, that the pathophysiology of  OSA is not so straightforward.   In fact, a more technical article at Medscape refers to it as follows: "Sleep apnea is a conundrum of causes and effects. New studies show that many causes become effects, and vice versa."  That "conundrum" is the kind of thing I used to blog about more often.  But today I am more inclined to stick to practical matters.

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