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Kathryn A. Myers, MD, discusses the clinical examination for obstructive sleep apnea.
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Kathryn A. Myers, MD, discusses the clinical examination for obstructive sleep apnea.
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Segment:0 .
[ Music ] >> Hello and welcome to JAMAevidence, our monthly podcast focused on core issues in evidence-based medicine. I'm David Simel, Professor of Medicine at the Durham Veterans Affairs Medical Center and Duke University. I am the editor of the Rational Clinical Exam Series, and today we're discussing sleep apnea. Joining me to talk about this topic is Dr. Kathryn A. Myers from Western University at London, Ontario.
Dr. Myers, to begin with, can you please explain the terms "obstructive sleep apnea" and "obstructive sleep apnea hypopnea syndrome" for our listeners? >> Sure. Obstructive sleep apnea is characterized by the nighttime cessation of breathing, known as apnea, or the reduction of airflow without cessation, which is known as hypopnea, and this is caused by obstruction of the upper airway. Obstructive sleep apnea syndrome is associated with symptoms such as excessive daytime sleepiness in addition to a significant number of nightly apnea and hypopnea events.
The gold standard for diagnosis of obstructive sleep apnea is full attended nocturnal polysomnography. And during this type of overnight sleep study, the number of apnea and hypopnea events per hour is reported as the apnea hypopnea index. An index greater than or equal to 5 is the diagnostic threshold for sleep apnea. When the index is between 5 and 15, sleep apnea is classified as mild. 15 to 30 is moderate, and above 30 is severe obstructive sleep apnea.
Asymptomatic individuals with at least 15 apnea or hypopnea events per hour are also diagnosed with obstructive sleep apnea because of the known adverse health consequences of moderate and severe obstructive sleep apnea. >> Well, there was a lot of data in your description of that. And one of the things I'd like to know, when I'm thinking about a patient, is what is the baseline prevalence of obstructive sleep apnea in the general population?
But from your description, I'm not sure which is the most relevant prevalence number, so can you help me with that? >> Well, the prevalence of sleep apnea varies based on the population studied, the threshold apnea-hypopnea index used and the presence or absence of symptoms. An apnea-hypopnea index of greater than or equal to 5, the prevalence of obstructive sleep apnea in community-based studies, is 14%. When the threshold is set higher at 15, the prevalence is 6%.
And when you add symptoms, such as excessive daytime sleepiness, in addition to the AHI above 5, the prevalence is between 2 and 4% in community-based samples. >> Well, I see a lot about recommendations for patients to get sleep studies, but I also know that there are several ways to get sleep studies done, one of which is doing them in the sleep laboratory in a formal way, but the other is doing home sleep studies, which we're hearing more about.
Can you tell me about the differences between a home sleep study and one done in a sleep laboratory? >> Yeah. So the full attended polysomnography is considered a level one study, but these are expensive, and there's limited availability, so home screening technologies have become more prevalent over the last few years. These technologies don't have the same reproducibility as nocturnal polysomnography. They don't measure sleep time.
And for this reason, an apnea-hypopnea index cannot be calculated. Instead, these tests use the number of desaturation events per hour of total recording time, and this is called a respiratory event index. Home technologies do misclassify some patients, and a recent study showed a false negative rate of up to 17%. And there are a significant number of technical failures of the equipment in the home, so many individuals will still need to proceed to a full sleep study.
Nevertheless, for immobile or frail individuals who cannot attend a sleep laboratory, this may be a useful alternative. The technology of home devices continues to improve, and it's likely that these technologies will be used more often in the future to assist us in the diagnosis of sleep apnea. >> Well, Dr. Myers, when I walk through my clinic, and I see visitors and patients, I often find myself thinking, "That one has sleep apnea, and that one has sleep apnea." And what I think I'm observing is obesity or patients with big necks.
When I'm in the exam room, what symptoms and signs should really alert me to think about sleep apnea-hypopnea syndrome? >> Sure. Well, individuals with sleep apnea tend to be older, they tend to be men with higher body mass index than those without sleep apnea, and many of them have hypertension, which is associated with sleep apnea but can also result from it. On its own, hypertension is not that useful as a diagnostic indicator for sleep apnea.
One thing that's important to ask is about motor vehicle collisions, as they have been associated with sleep apnea, especially moderate to severe sleep apnea. But unfortunately, there's no single symptom or sign that can reliably diagnose sleep apnea. Many of the symptoms we commonly associate with sleep apnea, such as morning headache and snoring and reported apneas, so fairly limited utility in making the diagnosis. The most useful symptom for identifying patients with obstructive sleep apnea was nocturnal gasping and choking, but even this symptom in our study was associated with only a modest positive likelihood ratio of 3.3. Similarly, although physical findings such as pharyngeal narrowing and higher Mallampati class are associated with sleep apnea, in our review, these showed limited contribution to our ability to diagnose sleep apnea.
It's important to remember, though, that there are certain craniofacial features that are associated with obstructive sleep apnea. There is a condition of overjet and retrognathia, and both are considered malocclusions. The first, overjet, occurs when there's 3 millimeters or more of anterior-posterior distance between the upper and lower incisors. Retrognathia is when there is greater than half a centimeter of retro position of the inferior chin, which is also known as the gnathion, relative to the superior aspect of the nasal bone, which is also known as the nasion.
So you've got retro position of the chin. Both overjet and retrognathia are associated with obstructive sleep apnea. >> Well, Dr. Myers, you mentioned snoring, and snoring is just so disruptive that it can be a driver for the patient's bedpartner to encourage me to evaluate a patient. Should snoring alone prompt a sleep study? >> Well, snoring is certainly a frequent complaint, and as you have said, it's often reported to us by the bedpartner rather than the patient.
I think it's important for clinicians to characterize snoring a bit more than just yes or no, one snores. It can be characterized by its frequency, its nightly duration, and its intensity. And so snoring that occurs daily throughout the night and can be heard down the hall is more likely to be associated with sleep apnea than occasional light snoring. Two large community studies of unselected adults reported the prevalence of snoring at 35%, so it's pretty common, and certainly much higher than the prevalence of obstructive sleep apnea syndrome.
Snoring on its own, as a single finding, though, really has little value in diagnosing obstructive sleep apnea. This was a remarkably consistent finding across six studies that we analyzed with a summary likelihood ratio of just above 1. This suggests that snoring on its own without any other risk factors or features to suggest sleep apnea should not prompt a sleep study. On the other hand, the absence of snoring makes sleep apnea less likely, especially in association with a normal body mass index.
>> Well, thanks. I hope my wife is listening to this. Tell me about the challenges clinicians face when diagnosing obstructive sleep apnea. >> I think that the biggest challenge facing clinicians is the fact that there's a lack of individual symptoms and signs that help rule in and rule out sleep apnea. This means that clinicians have to consider composites of these findings as well as clinical prediction rules to assist them in the diagnosis, and there are a number of these. There's the Berlin Questionnaire, the STOP-Bang, the Names-2 [phonetic], and these composites of signs and symptoms really are better at making sleep apnea less likely, but they're not very good at helping to rule in the diagnosis of sleep apnea.
So the clinician has to go to another source to look at a clinical prediction rule, and the sleep apnea clinical score is one that does help with diagnosis of sleep apnea. And it was developed from a regression analysis based on four variables that are fairly easy for clinicians to elicit. There's neck circumference, measured at the superior aspect of the cricothyroid membrane; the presence or absence of hypertension; nocturnal gasping and choking and habitual snoring.
And they developed a score, and scores above 15 have a positive likelihood ratio for sleep apnea of about 5, which is better than any individual symptom or sign that we analyzed in our study. In the original study as well, a neck circumference above 50 centimeters, which sounds fairly large but was found in their original study, was associated with a score above 15, so about finding on its own confers modestly increased risk of sleep apnea. >> Well, you've shared a lot of information with us today.
Is there anything else you would like to tell our listeners about the clinical examination for obstructive sleep apnea? >> I think it's important when deciding whether or not a patient should have a sleep study to consider an individual's occupation. For individuals who have mission-critical occupations where inattention due to sleepiness can have serious consequences, I have a lower threshold for ordering a sleep study. I think it's important to remember that we know treatment of sleep apnea lowers the rate of motor vehicle collisions, and so considering that question on the history I think is important and one we often forget.
>> Well, great. I really appreciate you taking the time to talk to us today. More information about this topic is available in the Rational Clinical Exam and in our website, JAMAevidence, all one word, dot com, where you can listen to our entire roster of podcasts. I'm David Simel, and I'll be back with you soon for another edition of JAMAevidence. [ Music ]
Segment:0 .
[ Music ] >> Hello and welcome to JAMAevidence, our monthly podcast focused on core issues in evidence-based medicine. I'm David Simel, Professor of Medicine at the Durham Veterans Affairs Medical Center and Duke University. I am the editor of the Rational Clinical Exam Series, and today we're discussing sleep apnea. Joining me to talk about this topic is Dr. Kathryn A. Myers from Western University at London, Ontario.
Dr. Myers, to begin with, can you please explain the terms "obstructive sleep apnea" and "obstructive sleep apnea hypopnea syndrome" for our listeners? >> Sure. Obstructive sleep apnea is characterized by the nighttime cessation of breathing, known as apnea, or the reduction of airflow without cessation, which is known as hypopnea, and this is caused by obstruction of the upper airway. Obstructive sleep apnea syndrome is associated with symptoms such as excessive daytime sleepiness in addition to a significant number of nightly apnea and hypopnea events.
The gold standard for diagnosis of obstructive sleep apnea is full attended nocturnal polysomnography. And during this type of overnight sleep study, the number of apnea and hypopnea events per hour is reported as the apnea hypopnea index. An index greater than or equal to 5 is the diagnostic threshold for sleep apnea. When the index is between 5 and 15, sleep apnea is classified as mild. 15 to 30 is moderate, and above 30 is severe obstructive sleep apnea.
Asymptomatic individuals with at least 15 apnea or hypopnea events per hour are also diagnosed with obstructive sleep apnea because of the known adverse health consequences of moderate and severe obstructive sleep apnea. >> Well, there was a lot of data in your description of that. And one of the things I'd like to know, when I'm thinking about a patient, is what is the baseline prevalence of obstructive sleep apnea in the general population?
But from your description, I'm not sure which is the most relevant prevalence number, so can you help me with that? >> Well, the prevalence of sleep apnea varies based on the population studied, the threshold apnea-hypopnea index used and the presence or absence of symptoms. An apnea-hypopnea index of greater than or equal to 5, the prevalence of obstructive sleep apnea in community-based studies, is 14%. When the threshold is set higher at 15, the prevalence is 6%.
And when you add symptoms, such as excessive daytime sleepiness, in addition to the AHI above 5, the prevalence is between 2 and 4% in community-based samples. >> Well, I see a lot about recommendations for patients to get sleep studies, but I also know that there are several ways to get sleep studies done, one of which is doing them in the sleep laboratory in a formal way, but the other is doing home sleep studies, which we're hearing more about.
Can you tell me about the differences between a home sleep study and one done in a sleep laboratory? >> Yeah. So the full attended polysomnography is considered a level one study, but these are expensive, and there's limited availability, so home screening technologies have become more prevalent over the last few years. These technologies don't have the same reproducibility as nocturnal polysomnography. They don't measure sleep time.
And for this reason, an apnea-hypopnea index cannot be calculated. Instead, these tests use the number of desaturation events per hour of total recording time, and this is called a respiratory event index. Home technologies do misclassify some patients, and a recent study showed a false negative rate of up to 17%. And there are a significant number of technical failures of the equipment in the home, so many individuals will still need to proceed to a full sleep study.
Nevertheless, for immobile or frail individuals who cannot attend a sleep laboratory, this may be a useful alternative. The technology of home devices continues to improve, and it's likely that these technologies will be used more often in the future to assist us in the diagnosis of sleep apnea. >> Well, Dr. Myers, when I walk through my clinic, and I see visitors and patients, I often find myself thinking, "That one has sleep apnea, and that one has sleep apnea." And what I think I'm observing is obesity or patients with big necks.
When I'm in the exam room, what symptoms and signs should really alert me to think about sleep apnea-hypopnea syndrome? >> Sure. Well, individuals with sleep apnea tend to be older, they tend to be men with higher body mass index than those without sleep apnea, and many of them have hypertension, which is associated with sleep apnea but can also result from it. On its own, hypertension is not that useful as a diagnostic indicator for sleep apnea.
One thing that's important to ask is about motor vehicle collisions, as they have been associated with sleep apnea, especially moderate to severe sleep apnea. But unfortunately, there's no single symptom or sign that can reliably diagnose sleep apnea. Many of the symptoms we commonly associate with sleep apnea, such as morning headache and snoring and reported apneas, so fairly limited utility in making the diagnosis. The most useful symptom for identifying patients with obstructive sleep apnea was nocturnal gasping and choking, but even this symptom in our study was associated with only a modest positive likelihood ratio of 3.3. Similarly, although physical findings such as pharyngeal narrowing and higher Mallampati class are associated with sleep apnea, in our review, these showed limited contribution to our ability to diagnose sleep apnea.
It's important to remember, though, that there are certain craniofacial features that are associated with obstructive sleep apnea. There is a condition of overjet and retrognathia, and both are considered malocclusions. The first, overjet, occurs when there's 3 millimeters or more of anterior-posterior distance between the upper and lower incisors. Retrognathia is when there is greater than half a centimeter of retro position of the inferior chin, which is also known as the gnathion, relative to the superior aspect of the nasal bone, which is also known as the nasion.
So you've got retro position of the chin. Both overjet and retrognathia are associated with obstructive sleep apnea. >> Well, Dr. Myers, you mentioned snoring, and snoring is just so disruptive that it can be a driver for the patient's bedpartner to encourage me to evaluate a patient. Should snoring alone prompt a sleep study? >> Well, snoring is certainly a frequent complaint, and as you have said, it's often reported to us by the bedpartner rather than the patient.
I think it's important for clinicians to characterize snoring a bit more than just yes or no, one snores. It can be characterized by its frequency, its nightly duration, and its intensity. And so snoring that occurs daily throughout the night and can be heard down the hall is more likely to be associated with sleep apnea than occasional light snoring. Two large community studies of unselected adults reported the prevalence of snoring at 35%, so it's pretty common, and certainly much higher than the prevalence of obstructive sleep apnea syndrome.
Snoring on its own, as a single finding, though, really has little value in diagnosing obstructive sleep apnea. This was a remarkably consistent finding across six studies that we analyzed with a summary likelihood ratio of just above 1. This suggests that snoring on its own without any other risk factors or features to suggest sleep apnea should not prompt a sleep study. On the other hand, the absence of snoring makes sleep apnea less likely, especially in association with a normal body mass index.
>> Well, thanks. I hope my wife is listening to this. Tell me about the challenges clinicians face when diagnosing obstructive sleep apnea. >> I think that the biggest challenge facing clinicians is the fact that there's a lack of individual symptoms and signs that help rule in and rule out sleep apnea. This means that clinicians have to consider composites of these findings as well as clinical prediction rules to assist them in the diagnosis, and there are a number of these. There's the Berlin Questionnaire, the STOP-Bang, the Names-2 [phonetic], and these composites of signs and symptoms really are better at making sleep apnea less likely, but they're not very good at helping to rule in the diagnosis of sleep apnea.
So the clinician has to go to another source to look at a clinical prediction rule, and the sleep apnea clinical score is one that does help with diagnosis of sleep apnea. And it was developed from a regression analysis based on four variables that are fairly easy for clinicians to elicit. There's neck circumference, measured at the superior aspect of the cricothyroid membrane; the presence or absence of hypertension; nocturnal gasping and choking and habitual snoring.
And they developed a score, and scores above 15 have a positive likelihood ratio for sleep apnea of about 5, which is better than any individual symptom or sign that we analyzed in our study. In the original study as well, a neck circumference above 50 centimeters, which sounds fairly large but was found in their original study, was associated with a score above 15, so about finding on its own confers modestly increased risk of sleep apnea. >> Well, you've shared a lot of information with us today.
Is there anything else you would like to tell our listeners about the clinical examination for obstructive sleep apnea? >> I think it's important when deciding whether or not a patient should have a sleep study to consider an individual's occupation. For individuals who have mission-critical occupations where inattention due to sleepiness can have serious consequences, I have a lower threshold for ordering a sleep study. I think it's important to remember that we know treatment of sleep apnea lowers the rate of motor vehicle collisions, and so considering that question on the history I think is important and one we often forget.
>> Well, great. I really appreciate you taking the time to talk to us today. More information about this topic is available in the Rational Clinical Exam and in our website, JAMAevidence, all one word, dot com, where you can listen to our entire roster of podcasts. I'm David Simel, and I'll be back with you soon for another edition of JAMAevidence. [ Music ]
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