When we have medical problems, we all want to understand the ‘who’, ‘how’ and ‘why’ of the condition. Knowing may lead to changes or corrections that might fix and potentially remove the problem. Many professionals have invested their careers studying obstructive sleep apnea (OSA), trying to understand the ‘hows’ and ‘whys’ of OSA. It remains a subject that few professionals agree upon. Perhaps it’s best to review the broad landscape of OSA before we look at the details; reviewing the forest before the trees. Let’s look at the ‘who’ of OSA.
OSA is a common condition. How many people have it and what are their characteristics? We have a general outline for the answers to these questions and it is best to start with an understanding of those facts. First, how common is it?
Investigators have studied and reported answers to our questions, but the answers seem to change with each report. There are real reasons for the differing answers. Depending upon the how the information was obtained, the answers will vary. The source of the estimates can be from formal research designed to uncover the answer, population studies of many types, questionnaire reviews, insurance data reviews, or combinations of these and other techniques. The frequencies reported range from highs of 50% from Germany and 37% from Switzerland, to lows of 3% in Australia. When reviewing these reports, one is struck by the differences in how people were selected for inclusion in the studies; the variations in the definitions used to label someone as having OSA and by the increasing level of its reported occurrence as the years passed and the condition became more commonly known.
The differences in these reports are not hard to understand. Each has a specific method to gather potential individuals into the report. Enrollment into the study varies. In many reports, the individuals have to volunteer to provide private medical information. Even the report from closed medical populations in countries with government run medical systems cannot identify cases if the individuals do not participate. The wise blind man can only grasp what he can feel and the wise investigator can only see what he has chosen to look at.
Another factor to take into account is how the report defines ‘having OSA’. Are test results required? If so, what kind of test and what parameters are necessary to establish the diagnosis? What level of OSA does the study accept? Does it include what is generally considered to be mild OSA (5-15 apnea event per hour)? Does it require the higher level of moderate OSA (greater than 15 event per hour) or does it include both and how are they reported? Each report varies.
Many details chosen by investigators will determine the population they report and thus, the prevalence of the condition. Reviewing for this presentation, I went to the National Library of Medicine website to look for appropriate information. My search identified 10,388 articles with information about the prevalence of obstructive sleep apnea.
Prevalence is the frequency of occurrence of something (in this case obstructive sleep apnea) in a selected defined population.
The important fact is that this condition is very common. How common is it? No consensus exists. The table below is constructed from several studies over the last 30 years and gives you an idea of reported values and how they have increased over the years.
I believe it is safe to say that at least 20 to 25% of adults in the United States have mild or greater apnea. Why the increase in prevalence with passing years? It is unclear, but most likely it represents the increase in awareness of the problem.
But, we need to be aware of still more details about who experiences OSA
Age is an important factor when measuring the prevalence of OSA. Few reports have elderly individuals participating. However, the report from Germany on 4,420 individuals from 20-81 years provides some answers. Half of the population had at least mild OSA and 20% had moderate or severe OSA. When broken down by age, 80% of men 70 y/o and older had some degree of OSA. The Swiss study also demonstrated a significant increase with age. Older studies do not show such a high prevalence in the elderly, but the majority of them did not include elderly individuals in the populations studied. Time will tell, but obstructive sleep apnea is very common in the elderly.
There is evidence that some ethnic groups may have more Obstructive Sleep Apnea than others. Particularly individuals of Southeast Asian or Black heritage. It is proposed that the cranial and facial boney structure in those groups leads to smaller upper airways.
What about occurrences during our youth and young adulthood? OSA is known to occur in infancy, childhood and during the teenage years. The prevalence for those ages is considered to be between 1 and 5%. As for early adulthood, there is substantial information from multiple reports to indicate it occurs in 5% to 8% of 18-30 year olds.
In the summary above I have used numbers that include both sexes. There is a significant difference in the occurrence of OSA between the sexes. In the report from Switzerland, 50% of men and 24% of women in the report had OSA. For most reports a significant difference between men and women is noted during the premenopausal years. With aging and menopause, the occurrence of OSA in women increases.
Summary – The Prevalence of Obstructive Sleep Apnea
The frequency increases with age in both sexes. After the age of 70, the occurrence rate is dramatic reaching up to 80% of adults in one study.
It is more common in men than women. After menopause the occurrence in females increases significantly
References:
Prevalence and association analysis of obstructive sleep apnea with gender and age differences. Fietze et al. J Sleep Res 2019 Oct; 28(5):e12770
Estimation of the global prevalence and burden of obstructive sleep apnea: a literature-based analysis. Benjafield et al. Lancet Respir Med. 2019Aug; 7(8):687-698
Prevalence of sleep-disordered breathing in the general population: the HypnoLaus study. R Henzer et al. Lancet Respir Med. 2015 Apr; 3(4): 310-318
Screening for Obstructive Sleep Apnea in Adults US Preventive Services Task Force Recommendation Statement. JAMA January 24/31 2017; 317(4) 407-414
Diagnosis and management of childhood obstructive sleep apnea syndrome. Marcus CL, Brooks LJ, Draper KA, Gozal D, Halbower AC, Jones J, Schechter MS, Ward SD, Sheldon SH, Shiffman RN, Lehmann C, Spruyt K, American Academy of Pediatrics. Pediatrics. 2012;130(3):e714.
Obstructive Sleep Apnea is a very common malady. It is familiar to many and is frequently a subject of both social and medical conversations. Individuals not engaged in frequent work with Apnea conditions may be confused by its usage and rightly so. Discussions and writings about the subject can use the term with different meanings. When used by professionals, it can also be used in various ways. It has a physiologic technical meaning; it is used as a proper name of medical conditions; and, it has a common usage that is less specific.
The word – apnea – comes from the Latin and Greek languages. The Latin ‘a + pnea’ means without breath and the Greek ‘apnoia’ means without pain. The Webster dictionary defines apnea as ”Transient cessation of respiration”. Webster’s definition fits well with the current technical use of the word, but fails to show the scope of the word’s use that has increased over the past half-century with the recognition of the associated clinical conditions.
Webster’s definition fits well with the current technical use of the word, but fails to show the scope of the word’s use…
The word is used technically to label a cessation of breathing. Sleep testing, in facilities or at home, and physiologic monitoring of hospital patients can identify periods when no air is going in or out of the nose or mouth. No breaths can be measured. These events are called Apneas.
The word is used technically to label a cessation of breathing.
The addition of chest movement measurements during these apnea events further defines these periods of apnea. If the breathing efforts are persistent during an apnea episode, the event is labeled an Obstructive Apnea. If no breathing efforts are being made by the chest, the pump that moves air in and out, the apnea is caused by the lack of chest effort and is called a Central Apnea. It is called central because breathing effort by the chest is controlled, started and adjusted, by the Central Nervous System. If the breathing problem is associated with both partially reduced chest movement and total cessation of movement, it is labeled a Mixed Apnea. As we can see, the technical apnea breathing events are further defined as obstructive, central or mixed.
‘Apnea’ is used as part of the proper name of medical conditions
‘Apnea’ is used as part of the proper name of medical conditions. These conditions were described and first recognized approximately a half-century ago, but probably have been affecting mankind for our entire history. Obstructive Sleep Apnea is the first of these. When breathing is blocked or partially blocked for 10 seconds at least five times per hour, a diagnosis of the clinical syndrome of Obstructive Sleep Apnea is established.
Central Sleep Apnea is the clinical condition where the primary form of apneas measured is central. It is established when a certain percentage of the physiologic apneas recorded on testing are the central type. Central Sleep Apnea can be the result of multiple medical issues that range from cardiovascular problems to neurologic conditions. It can be rarely seen on its own and not associated with other medical problems.
A third commonly accepted diagnostic term is Complex Sleep Apnea. This diagnostic group represents individuals with obstructive sleep apnea treated with CPAP whose breathing events do not resolve when they are treated. Their Apnea Hypopnea Index remains high. However, on repeated testing with CPAP, the breathing events are now predominantly Central Apneas. The CPAP treatment caused a change from Obstructive Apnea events to Central Apnea events. This type of medical condition is called Complex Sleep Apnea.
The term Apnea Hypopnea Index (AHI) may be new to some, but it is very important that it is understood. The ‘Apnea’ referred to is the physiologic measured Apneas. ‘Hypopnea’ is a partial obstructive breathing event measured on testing. They have the same secondary effects as apnea events but without the total cessation of airflow. The AHI is a calculated number representing the total events (Apnea and Hypopneas) per hour.
The AHI is the measurement on a diagnostic sleep test that determines if an apnea condition of some type is present. With a patient on therapy, it is the number that is followed by the physician to determine how well the therapy is working. It is measured on most CPAP machines and can be reviewed by the patient on a day-by-day basis. The AHI on a diagnostic test is and has been the measurement to determine the severity of sleep apnea conditions for many years. The AHI is an example of the technical use of the word apnea.
…the common use of the term Apnea is far less specific…
Finally, the common use of the term Apnea is far less specific than the uses we have reviewed. Often, the word is used to encompass a broad range of the field. In writings and conversations, it will be used by an author as a single word to cover all, or one, of the apnea medical conditions – obstructive sleep apnea, central sleep apnea and complex sleep apnea. When discussing Obstructive Sleep Apnea conversationally, most will speak about apnea, meaning obstructive sleep apnea. The most simple descriptive of its common use is as a substitute for the clinical conditions associated with breathing problems during sleep.
What we have covered.
1. Apnea is technically an absence of breaths (no airflow at the nose and mouth).
2. Apnea, used technically, during sleep is further defined by its features to be obstructive, central or mixed.
*Obstructive apnea
*Central apnea
*Mixed apnea
3. Apnea is used in the formal name of medical conditions including:
*Obstructive Sleep Apnea
*Central Sleep Apnea
*Complex Sleep Apnea
4. Apnea, used in its technical manner, is a component of the Apnea Hypopnea Index measurement used to judge the severity of the problem.
5. Apnea’s common use is as a general term covering one or all of the clinical conditions
“Why am I using that this thing?” they asked me. This ‘thing’ they were referring to is also known as CPAP.
Many people find themselves having had a sleep test and they are not sure why. They have a CPAP machine (Constant Positive Airway Pressure machine). Yet, they tell me, “I don’t know why.” Yes, they’ve been told they have apnea (Obstructive Sleep Apnea or OSA), but why do they need to do this? It is a question that they should be able to answer. Why do we use CPAP? Why do we treat OSA?
Why do we treat OSA?
When a sleep evaluation or sleep testing was considered for you, your physician felt it might explain some of your sleep related symptoms or medical problems. It might have been for snoring that you were not even aware had been occurring. Maybe you were sleepier than you wanted to be or more sleepy than your family or friends thought you should be. It could have been for another non-related issue. Your doctor was concerned that your problem with glaucoma, asthma or hypertension may have been made worse by or possibly even caused by a sleep condition. The test was ordered. Obstructive Sleep Apnea was found and now you have a CPAP machine.
Obstructive Sleep Apnea may cause symptoms. Excessive sleepiness, poor quality nocturnal sleep and waking up with headaches are just a few of these symptoms. Your snoring could be waking your spouse. Certainly, you would prefer not to have the symptoms. You want to sleep better and to feel better during the day.
One of the major goals of therapy for OSA, including CPAP, is to improve or eliminate symptoms. When the obstructive apnea is corrected, many of its symptoms resolve or improve, sometimes dramatically. If you had symptoms when your apnea was diagnosed, one goal of therapy is to improve or correct those symptoms.
Most symptoms of OSA are not specific.
Most symptoms of OSA are not specific. A wide range of medical conditions, some common and others not so common, can cause these symptoms. It is unfortunate, but our sleepiness or headaches do not come with labels telling us what is causing them to occur. Often, sleep apnea treated with CPAP will totally correct the obstructive events, but the symptoms that led to the evaluation and testing do not go away.
Many patients at the time they are diagnosed with significant obstructive apnea will have few or no symptoms. These individuals have varying degrees of OSA severity on their sleep testing. Surprisingly, significant OSA can be seen with minimal symptoms or even no symptoms. While the number of obstructive events per hour will generally be related to the severity of the symptoms, is it not unusual to see patients with both moderate and severe apnea with few symptoms. Even without symptoms, our current knowledge strongly supports the need for their treatment.
Many patients at the time they are diagnosed with significant obstructive apnea will have few or no symptom.
Understanding the reason for treating individuals with few or no symptoms requires a little more information. Obstructive Sleep Apnea is the repeated interruption of someone’s breathing while asleep. The obstructions result in a blood oxygen drop and an arousal to light sleep or brief awaking. These arousals are not usually associated with full awakenings. Most individuals are not aware that the obstructions have occurred.
There are two types of obstructions. The first is a total blockage of the airway with a drop in blood oxygen level while breathing efforts from the chest continues. The technical term for complete obstruction is Apnea. The second is a partial blockage of the airway while the breathing continues. These partial blockages cause the same problems as seen with an apnea. The technical term for the partial obstruction is Hypopnea. The two types of obstruction are measured during a night or portion of a night of sleep testing. The numbers of each are added together. When divided by the duration of the sleep where the measurements were made, the results represent the number during an average hour of sleep. The resulting number is the Apnea-Hypopnea Index or AHI. The AHI is the average number of apneas and hypopneas in one hour of sleep.
The AHI is considered a measurement of the severity of Obstructive Sleep Apnea. Other factors enter into the measurement of severity. The most common would be the degree of oxygen drop that occurs with these obstructive events. It is generally accepted that an AHI of less than 5 is not considered to be diagnostic of OSA. An AHI of 5 to 15 events per hour is considered mild OSA. An AHI of 15 to 30 is moderate and above 30 is severe Obstructive Sleep Apnea.
The AHI is considered a measurement of the severity of Obstructive Sleep Apnea.
In the past 40 years, thousands of research studies on Obstructive Sleep Apnea have been performed. The vast majority utilize the severity scale noted above. Those studies strongly support the current concept of the role of apnea in causing and aggravating other medical conditions.
The higher a person’s AHI on their diagnostic sleep test, the more likely they will die from a stroke or heart attack. The risk is far higher than those who have no obstructive sleep apnea. And, they die younger. When the AHI is greater than 15 per hour the risk is significant. An increased risk is measurable at an AHI of five but it is relatively small. It is very small at an AHI of less than five. It is generally accepted the long-term treatment of patients with an AHI greater than 15 at the time of diagnosis will improve secondary medical conditions and prolong life.
The second goal of therapy is obvious. It is to reduce or eliminate as many apnea and hypopnea events as possible. A person with OSA cannot know what their AHI is on any given day, night, week or month. As noted above, the symptoms do not always reflect the success of OSA treatments. However, with modern CPAP machines, technology can measure those events (AHIs) while you use the machine. Reports are now available on most machines, on most machine manufacturer’s websites, or through your physician. You and your physician can know how well your therapy is controlling your AHI.
What have we covered.
1. Obstructive Sleep Apnea can occur with minimal or no symptoms.
2. Obstructive Sleep Apnea is treated for two reasons
3. Obstructive Sleep Apnea treatment may only improve one of the reasons it is being treated.
4. The Apnea Hypopnea Index (AHI) is the number of obstruction events per hour of sleep.The AHI while on therapy demonstrate how well the therapy is controlling the Obstructive Sleep Apnea.
Three questions follow naturally from this brief review. These topics will be addressed in future post.
1. Why do I still have symptoms on treatment for OSA?
2. If I have mild OSA when diagnosed, do I need treatment?
3. What is the definition of apnea?
Why is OSA treated? The two reasons are: to improve symptoms and control the obstructive events. When we treat OSA, the treatment may be successful treating both, or just one of the two. One or both may be the reason CPAP, or another treatment, was recommended for you.
I am reminded of a cartoon from the 1960’s. People can be seen bowing before an altar, an empty altar, with the name ”Nothing” on it. On the top of the altar, there is nothing. It is empty. In the rear looking towards the altar, one person whispers a question to a second person, “Is nothing sacred?”
Science is not sacred. Science is not a thing. Science is a process, a technique, and a method to study problems, questions, theories and their solutions in an organized manner. What then are scientists? They are people who use the method. They are individuals from almost any field of human endeavor doing research in their fields of interest. But, most of all they are humans.
“Is nothing sacred?”
We are washing our hands more these days. Coronavirus has seen to that, but it was not always so. There was a time in human history when, among doctors, it was not thought fashionable, necessary, or appropriate to wash hands. In fact, the presence of bloody debris on doctor’s clothing and hands was a sign of importance.
A physician in the 1840s, Dr. Ignaz Semmelweis, observed and studied a problem with infections in labor and delivery at Vienna General Hospital. Infection rates and mortality rates for women having their babies in the hospital were extremely high. His observations led him to believe that maybe the doctors themselves were transferring infections to patients in the hospital. He implemented what we would consider to be basic hygiene steps and instituted hand washing for the doctors between each patient’s evaluation and exam. The changes resulted in a dramatic improvement. Infection rates, in the area of the hospital where this was used, plummeted.
Unfortunately, this was not well received. The doctors working at his time in history would not accept his observations and facts. Dr. Semmelweis was shamed, belittled and driven from the profession. Many decades would pass and many others would confirm his work before the value of hand washing was accepted by the medical profession.
…shamed, belittled and driven from the profession.
Change is difficult to accept. Belief in the change has to occur before it can be accepted. A scientific study is a man-made creation. One fact is studied, but multiple measurements are made. The measurements are reviewed and conclusions are reached by men. Can other researchers duplicate the results? The process of science is a back-and-forth path. Even when a fact becomes established and proven to be verifiable, it may not be accepted into practice for many years. Likewise, established facts or practices that are proven wrong by new research will not be discarded untill many years or decades pass. In each case, the delay is often the result of other more human reasons.
Well-designed scientific studies in medicine and its related fields are large and very expensive endeavors that can last several years. They require years of commitment and dedication from the researchers. Reputations, careers, professional positions, titles, rewards and not the least, egos, become established, glorified, tarnished and destroyed based on scientific study results and positions taken regarding those results. Unsurprisingly, human behavior enters into acceptance. When the facts are not clear or not definitive, time is required for new studies to provide new information or knowledge about the subject. The factual debate may last years, decades, or even centuries. Unfortunately, strong personalities expressed through loud voices with bully pulpits will often sway the profession, government or public to positions that do not tell the entire or accurate story. It can be, as in Dr. Semmelweis’ case, decades before a truer picture is known.
Public awareness of papers by researchers in any field is usually limited to observing the results of those studies and the generally accepted facts of the time. The scientific review process is not generally in the public view. The back-and-forth, the arguments, the clashing of the egos, has been carried out without public awareness. Now the new coronavirus pandemic is unfolding before us. The airways and social media are full of studies, opinions and arguments regarding the appropriate approach to diagnosing, treating and preventing coronavirus infections. The chaos you hear is real because no one knows what the elephant looks like. Like the blind men describing an elephant, each has his hands on some limited part of the animal’s anatomy, but the full picture will not be known for some time.
The chaos you hear is real…
One thing should be kept in mind. Medicine and its practice remains a learned art that applies experience, knowledge and technology to help humans manage their sufferings. Scientific facts have improved those skills and the techniques used to treat and assist those in need. Remember, while today’s reported scientific facts may indicate future practices (Semmelweis and hand washing), it may represent one person’s need for recognition and praise ultimately signifying nothing.
This scientific noise about the coronavirus will settle with time and a truer picture of what it means will become clearer. For the time being, the noise is being amplified by our politicians and media that have little experience in things medical and have their own needs for recognition. Do not expect that to change soon.
Are you at increased risk of a serious coronavirus infection if you have obstructive sleep apnea? No one knows, although one day that information will be available. What do you do when placed in a situation with an unknown that can affect you drastically? What we always do; look for information and compare it with our previous similar experiences. Leaving our home for a day’s activity when the clouds are dark and rain is in the forecast, it is only smart to take along the umbrella or raincoat. The same is true for the coronavirus. We need to consider:
What do the experts tell us?
What is our experience with other infections?
Experts
The experts tell us coronavirus is a contagious respiratory infectious agent. It may cause life-threatening illness and it also may infect people without causing illness. The number infected is not known and the percent of life threatening illnesses is not established, but it is gradually appearing that it is a smaller percentage than was initially predicted.
What causes some to be very ill and even die? The picture is becoming clearer with time. The elderly, the chronically ill, the immunosuppressed and others with poor health are more likely to be severely ill. The death rate for those individuals is much higher than for the population in general. In some areas, over half of those who die with the illness are from these groups.
Are there others? Yes there are. We have heard the ‘news’ reports about them. Why in otherwise healthy individuals can the infection cause severe illnesses? Experts can only speculate on the subject. The possibilities include exposure to a heavy dose of the virus. A heavy dose is more likely to make someone severely ill than a lighter dose. The healthy person may have unrecognized underlying medical conditions. They may have an unrecognized deficiency in their ability to fight off this specific type of viral infection. For most of these unfortunate individuals, no one will be able to explain why.
We do know that heart disease, hypertension, diabetes and obesity are frequently cited as problems associated with dying from an infection with the coronavirus.
Experience
What does our experience tell us? A common experience most of us will have is with influenza. In fact, as time passes, coronavirus has begun to act like a severe influenza. Coronavirus is more contagious than influenza, but it is beginning to appear to have a similar mortality. There is no immunization available at present to prevent the illness and it is certainly best to avoid catching it.
Older individuals are familiar with other infectious agents. Some will remember polio, SARS, H1N1 (swine flu) and the early concerns about HIV. With knowledge and experience, we have learned to live with some of these problems, to treat some and to watch as others pass from importance. So it will be with the coronavirus.
Obstructive sleep apnea and coronavirus
What about you as an obstructive sleep apnea patient? You should listen to experts and rely on experience. As a specialist in sleep medicine, I would advise you that obstructive sleep apnea is an underlying medical condition that places you at increased risk of a more severe infection if you contract the coronavirus. In addition, many individuals with obstructive sleep apnea also have hypertension, diabetes and weight problems. Hypertension, diabetes and weight problems are known risk factors for severe coronavirus infections.
We know that patients with untreated sleep apnea have more respiratory infections. They develop problems with many chronic illnesses. These problems are related to the severity of their apnea. The number of obstructive breathing events per hour (the apnea hypoxia index) without treatment is a measure of the underlying severity. The more events recorded the more severe your apnea. It is a fact that patients successfully treated with CPAP have less respiratory infections and fewer complications from chronic illnesses.
I suspect these facts will prove to be the same for the coronavirus. Untreated significant apnea will prove to be a risk factor for developing severe coronavirus infection . However, successfully treated patients should have substantially less risk.
In summary
Having obstructive sleep apnea increases the risk of a severe coronavirus infection.
The risk will increase with the severity of the apnea.
Treatment of apnea will reduce the risk.
If you have apnea, consider yourself to be at increased risk for a coronavirus infection.
