The answer to the question – what is sleep apnea – is not cut-and-dry. The reason is the term sleep apnea can mean an event or a disorder. To define sleep apnea as an event it is first necessary to explain the meaning of the term apnea. Apnea is the cessation of breathing. Therefore, sleep apnea as an event is the cessation of breathing during sleep.
On the other hand, sleep apnea as a disorder or syndrome is a chronic pattern of breathing interruptions along with other physical and chemical abnormalities in the body which occur during sleep. The disturbed breathing can be apnea, hypopnea, or a combination of the two. In contrast to the disorders though, sleep apnea syndromes can be associated with more complex abnormal breathing patterns.
What causes sleep apnea?
There is an abundance of literature about the cause of sleep apnea. It doesn’t really explain the cause though, which is unknown. Instead, it focuses on the pathophysiology of the events. Nevertheless, knowing what happens when breathing ceases helps to recognize and understand the two types of sleep apnea disorders as well as the different sleep apnea syndromes. The 2 types of disorders are obstructive sleep apnea (OSA) and central sleep apnea (CSA).
In obstructive sleep apnea (OSA) there is excessive loss of tone or relaxation of the muscles of the throat. There is normally some relaxation of those muscles during sleep. But the excessive degree to which it occurs with OSA causes the structures in the mouth and throat to collapse into the airway totally or partially cutting off the flow of air. The obstruction can be behind the palate, behind the tongue, or below the pharynx. Tonsillar tissue might contribute to the obstruction in children and young adults.
Central sleep apnea (CSA) though, is not a problem of upper airway obstruction. Rather, the alteration in breathing is one of absent or reduced effort. The pathophysiology is a disturbance of the signals within the CNS that control the breathing muscles. But the cause is not known.
Central sleep apnea syndrome (CSAS) is a pattern of altered and abnormal breathing resulting from various diseases. Depending on the disease causing it, breathing abnormalities might be apnea and hypopnea typical of CSA or those abnormalities in conjunction with Cheynne Stokes respiration. Some of the more common conditions and diseases recognized as causing CSAS are the following.
- High altitude breathing
- Structural disease or injury to the brain
- Congestive heart failure
- Kidney failure
- Neuromuscular disorders such as Lou Gehrig’s disease
- Other nervous system diseases such as Parkinson disease and Alzheimer’s disease
- Opiate narcotics and other medications that suppress the central nervous system
Sleep apnea risks versus causes
Despite the fact that the cause of obstructive sleep apnea is unknown, there are various risk factors which increase the chances of developing or having it. The most firmly established one is obesity – defined by a body mass index of greater than 30 kg/m³. Despite the strong link, it is worth noting that obesity is not the sole determinant in the development of OSA. The reasons are not every obese person has OSA and it does develop in individuals who are not obese.
Other risk factors for developing OSA are the following:
- A neck circumference greater than 17 inches in man and greater than 16 inches in women
- A smaller than normal upper airway
- And upper airway formed in the shape of an ellipse rather than a true circle
- An enlarged tongue
- Prominent tonsils
- Various structural abnormalities of the head and face.
OSA is most common in the pediatric population and in individuals who are middle-aged. The prevalence of the disease in adults increases with age until around age 65 where it plateaus. The condition is 3 to 5 times more prevalent in men than in women. Structural abnormalities of the face or head which are risk factors include an undersized jawbone, malpositioning of the jawbone, and a deviated nasal septum.
Sleep apnea statistics
Obstructive sleep apnea is considerably more common in the general population than most would think. An estimated 17% of the general adult population has OSA – a percentage which experts in the field estimate will continue to rise with the obesity epidemic. According to current figures almost one in 15 adults has at least moderate sleep apnea, 85% of which are undiagnosed based on recent estimates.
Primary central sleep apnea is much less common. Based on statistical studies, it is present in less than 1% of the general population and less than 10% of people who undergo a sleep apnea test. The frequency of some of the central sleep apnea syndromes is much higher though. For example, one study showed that central sleep apnea symptoms are present in 30% of patients in a stable methadone maintenance program.
Effects of sleep apnea on health and lifespan
What are the effects of sleep apnea on my health? Can you die from sleep apnea? These are legitimate questions that many ask. The answer to both questions in a nutshell is there is significant morbidity and mortality associated with untreated sleep apnea. This need not be the case though. The difference maker is treatment. The treatment that makes the difference is continuous airway pressure (CPAP).
The increased morbidity is in the frequency and adverse outcomes of certain diseases. Those diseases are primarily type 2 diabetes mellitus and cardiovascular disease. The cardiovascular diseases include hypertension, coronary artery disease, congestive heart failure, arrhythmias and stroke. There are also some other conditions for which outcomes are worse in individuals with sleep apnea. They are gout, mood disorders, and brain disorders which cause deficits in mental processes.
In its seventh report the Joint National Committee on Prevention Detection, Evaluation, and Treatment of High Blood Pressure listed sleep apnea first on its list of causes of hypertension. Research has shown that high blood pressure tends to develop in 45% of individuals within four years of the diagnosis of OSA. Also, 80% of people with high blood pressure which is difficult to control have OSA. Studies have shown that treatment with CPAP lowers blood pressure and improves control, even in individuals with difficult to control hypertension.
There is a growing body of data which links sleep apnea with type 2 diabetes mellitus and its forerunners, insulin resistance and impaired glucose tolerance. There is not absolute proof of a cause-and-effect relationship. But some research indicates there might be. Other research has shown that CPAP therapy immediately improves insulin sensitivity and lowers blood glucose and hemoglobin A-1 C levels.
According to research the risk of developing cardiovascular disease is greater in individuals with sleep apnea. That risk is independent of other risk factors such as smoking, high blood pressure, age and obesity. Studies have also shown an increased risk of fatal and nonfatal cardiovascular disease events. One such study revealed a risk which was three times greater in patients with untreated OSA compared to treated patients and patients without the disease whose risks were equal.
Various studies have shown greater recurrence of atrial fibrillation in untreated patients with OSA who had undergone previous successful cardioversion. In one study the recurrence rate was higher than 80% for patients who were not treated. That figure compared with 50% of patients who received treatment and patients who did not have OSA. Other studies have also shown a correlation between the risk for various types of arrhythmias and the severity of OSA.
The Sleep Health Heart Study showed that patients with OSA have a 3-4 fold increased risk of heart failure, even when adjusted for other risk factors. Nonetheless, CPAP treatment improves function of the left ventricle in sleep apnea patients with heart failure.
Untreated OSA is also associated with an increased risk for ischemic stroke. CPAP treatment also reduces that risk to a major degree.
The increased mortality of untreated sleep apnea is four-pronged. First of all, death is greater because of the increased incidence of cardiovascular and other diseases along with their increase in adverse outcomes. Secondly, individuals with OSA have a greater occurrence of sudden cardiac death at nighttime. Thirdly, there is an increased overall death rate associated with sleep apnea which is independent of other risk factors. It is most evident in men. Fourthly, people with OSA are more likely to be involved in motor vehicle accidents, some of which are fatal.
Pathophysiology of sleep apnea morbidity
Research has discovered many disturbances in the physiology of patients with untreated OSA, which presumably are responsible for much of the increased morbidity of the disease. The main ones are fluctuations in oxygen levels, altered sleep, and changes in the function of the autonomic nervous system. Some relevant pathways possibly linking OSA with increased morbidity are as follows.
- Intermittent hypoxia activates the sympathetic nervous system which causes constriction of the pulmonary arteries. The result is elevated pressure within those vessels which places an increased load on the right ventricle of the heart.
- Rises in blood pressure and heart rate following apneic events are associated with fluctuating parasympathetic and sympathetic nervous system activity.
- Intermittent hypoxia followed by excessive oxygenation resulting from overshoot breathing is an ideal condition for the formation of free radicals which can damage heart cells.
- Research has linked OSA with an increase in the number of mediators and indicators of inflammation.
- Research has also drawn a correlation between OSA, an increase in the amount of substances in blood that prevent clots, and an increase in the number of those that cause clots to form.
Signs and symptoms of sleep apnea
Recognizing the common signs and symptoms of sleep apnea is oftentimes the first step for an accurate and timely diagnosis. Some symptoms are noticeable only at nighttime. Others are noticeable during the day. Some are specific for OSA but many overlap with OSA, CSA and CSAS. Snoring and some the other manifestations listed below can be either signs or symptoms. They are symptoms if recognized by the person experiencing them. They are signs when someone else witnesses them.
Signs of sleep apnea
Common signs of sleep apnea are as follows:
- Witnessed apnea (50%-60%)
- Disruption of a bed partner’s sleep
- Personality changes
Sleep apnea symptoms
Common nighttime symptoms are the following:
- Restlessness (90%)
- Snoring (78%)
- Dry mouth (74%)
- Drooling (36%)
- Excessive nighttime urination (28%)
- Choking or shortness of breath (18%-31%)
- Profuse sweating (25%)
- Gastroesophageal reflux symptoms (25%)
Common daytime symptoms are:
- Excessive daytime sleepiness
- Morning headaches (50%)
- Poor concentration
- Decreased sex drive
- Nasal stuffiness
- Decreased sex drive (35%)
- Decreased attention span
How a sleep apnea diagnosis is made?
The sine qua non for making a sleep apnea diagnosis is a sleep apnea test. Polysomnography is the name of the test. A list of the required equipment for the test is the following:
- Electromyography (EMG) to measure electrical activity in the chin as a determinant of the onset of sleep and to measure leg movements during sleep
- Electroencephalography (EEG) to measure electrical activity of the brain
- Electrooculogram (EOG) to record eye movements which are important determinants of the different sleep stages, particularly REM sleep.
- Pulse oximetry to measure oxygen saturation
- Electrocardiogram (EKG) to record heart rate and rhythm
- A nasal airflow sensor to measure airflow
- Snore microphone to record snoring
- Chest and abdominal belts to measure breathing
Not only can this sleep apnea test distinguish between the sleep apnea disorders and syndromes. It will sometimes show that individuals with OSA also have some central events and vice versa. Findings specific for the disorder or syndrome diagnosed will predominate though. This overlap in pathophysiology observed during testing can explain why some people with CSA might snore, although to a much lesser degree than those with OSA.
The apnea hypopnea index (AHI) is a metric for diagnosing and grading the severity of obstructive sleep apnea. It is the total number of episodes of apnea and hypopnea divided by the total sleep time in hours. Obstructive events during testing must last at least 10 seconds and occur at a frequency of at least 15/h, with one exception, in order for a diagnosis to be made or confirmed. The exception is a diagnosis can be made based on 5 events per hour if one of the following is true:
- The test recipient reports daytime sleepiness, daytime dozing off, unrefreshing sleep, fatigue, or insomnia
- The test recipient reports waking up with breath-holding, gasping, or choking
- An observer reports loud snoring or breathing interruptions on the part of the test recipient.
The grading scale for the severity of OSA based on the AHI is as follows:
|Severity||AHI||O2 Sat||EKG Findings|
|Mild||5-15 vents per hour||> 85%||Mild fast or slow heart rate|
|Moderate||15-30 events per hour||75-85%||Faster or slower heart rate, asystole < 3 seconds|
|Severe||30 or greater events per hour||< 75%||Asystole > 3 seconds, ventricular tachycardia|
The third and fourth columns of the above table show the correlation between severity of OSA based on AHI and other measures of severity. Those markers are the degree of drops in oxygen and the severity of abnormalities of heart rate and rhythm which occur during apneic events.
The home sleep apnea test
For a number of reasons many individuals that need to be tested desire an alternative to the gold standard sleep apnea test. The home sleep apnea test is that option, but it is more limited than standard polysomnography. It monitors only airflow, effort and oxygenation. Its use is for adults with a high likelihood of having moderate to severe OSA. It is not for screening of individuals without any signs or symptoms of OSA, nor is it for individuals with coexisting sleep disorders such as CSA, CSAS, or insomnia. It is also not for the testing of patients with moderate to severe heart failure, other cardiac disease, moderate to severe pulmonary disease, or disease of the nervous system with symptoms.
A mnemonic that healthcare professionals used to predict the probability of OSA and to decide the appropriateness of home testing is STOP-BANG. Below is an illustration of it.
|Snore||Has anyone ever told you that you snore?|
|Tired||Are you frequently tired during the day?|
|Obstruction||Do you know or has anyone witnessed that you stop breathing while you are asleep?|
|Pressure||Do you have high blood pressure or are you taking medication to control your blood pressure?|
|Body mass index||Is the patient’s body mass index greater than 35 kg/mm³?|
|Age||Is the patient 50 years are older?|
|Neck||Is the patient’s neck circumference greater than 17 inches if a male or greater than 16 inches if a female?|
|Gender||Is the patient a male?|
Three or more positive responses predict a high probability of OSA prior to testing.
Sleep apnea treatment options
Continuous airway pressure (CPAP)
CPAP is continuous delivery of pressurized air to the upper airway to prevent its collapse during sleep. A sleep apnea machine generates the air and delivers it through a tube connected to a device which covers an opening to the airway. It is the treatment of choice for OSA and is successful in 95% of patients who use it properly. One of the problems with proper use is consistency.
CPAP side effects and options
CPAP side effects are oftentimes the cause of poor adherence with its use. They include CPAP mask discomfort, stuffy nose, pressure intolerance, air swallowing, skin irritation from wearing the mask, and machine noise.
Because of CPAP mask discomfort different designs of masks are available. One covers the nose only. Another covers the mouth and nose. For individuals with claustrophobia a nasal pillow mask which does not cover the face is an option. Nasal prongs are also available.
Bilevel positive airway pressure (BiPAP) is an option for individuals with pressure intolerance and air swallowing associated with CPAP. The lower pressure load during exhalation is what helps.
If stuffy nose is a side effect the use of a sleep apnea machine which provides heated humidification might be a solution. Other options include nasally applied saline, gel or corticosteroids.
If skin irritation from wearing the sleep apnea mask is a side effect a mask without silicone or a barrier between the silicone seal and the face with a material such as moleskin is an option.
CPAP or BiPAP machine noise is not that much of a problem these days with the newer model machines, but if it is a problem, a white noise device or earplugs are options.
Weight loss as sleep apnea treatment
Weight changes have a definite effect on the severity of OSA. According to research data, a 10% weight loss correlates with a 26% decrease in the AHI. Conversely, a 10% gain in weight is associated with a 32% increase in the AHI. Some studies have suggested that bariatric surgery of varying types can cure OSA in 75% to 85% of the cases. Another study comparing patients achieving weight loss through diet with those losing weight following surgery showed no difference in the AHI between the 2 groups, even though the patients that underwent surgery lost more weight.
Medications and sleep apnea treatment
There is a single medication for treating CSA but none for OSA. The role of medications in the case of OSA is rather one of avoidance. Medications to avoid are alcohol, narcotics and tranquilizers because they cause too much relaxation of the muscles of the upper airway.
Sleep hygiene is a form of supplementary treatment which is often beneficial. It is behavior that promotes sleep. It includes not watching television in bed, waking up at the same time in the morning, and avoiding drinking caffeine within 4-6 hours of going to bed.
Positional therapy should also be a routine behavior. It involves avoiding lying on the back during sleep because doing so seems to aggravate OSA. Gravity and airway anatomy seem to play roles.
Other sleep apnea treatment options
The sleep apnea mouthpiece is an oral device used to keep the airway open and prevent snoring while sleeping. There are basically 2 types. One forces the lower jaw forward and slightly downward. The other holds the tongue in place to help keep the airway open. There is scientific evidence that both types reduce snoring and improve sleep. But evidence is lacking with respect to whether or not they improve long-term cardiovascular morbidity.
Other forms of sleep apnea treatment are reserved for sufferers who either cannot use CPAP or don’t benefit from using it. They include various surgical procedures of the mouth and throat cavities, tracheostomy and removal of the tonsils and adenoids (of children).
Some newer forms of treatment are in the early stages of use. They include the nasal expiratory positive airway pressure device, oral pressure therapy, and stimulation of the 12th cranial nerve. Although they all improve some aspects of OSA according to research, none is as effective in improving OSA severity as CPAP.
Except in rare cases, supplemental oxygen is usually not effective for treatment of OSA, particularly in terms of improving outcomes of cardiovascular diseases. Therefore, it is not first line treatment.
Patient engagement in sleep apnea treatment
Meaningful patient involvement in the management of OSA is not just wearing a sleep apnea mask at nighttime and keeping doctor appointments. It should include monitoring and recording changes in the signs and symptoms of the sleep disorder and its comorbidities. Examples include keeping a record of blood glucose readings, weight changes, blood pressure readings and any changes in the frequency of snoring and apneic events witnessed by others.
When physicians have knowledge of the type of information just described it helps them provide better care and make necessary changes in the management of the disease. One such change might be reassessment of the need for CPAP.
Finally, proof of benefit from the use of CPAP is a current Medicare requirement for reimbursement. The benefit must be between the 31st and 91st day after treatment has begun. In light of Health care Reform and other changes in the health care field, it is very likely that proof of benefit from services for a variety of conditions will be an industry requirement for reimbursement in the near future. If so, the type of documentation patient engagement produces should help doctors and patients rise up to the challenge.