Sleep Apnea and Hypopnea - Sleep Issues

What are Sleep Apnea and Hypopnea?


Most of us would like to have a good night’s sleep night after night. However, there are many of us who do not sleep well. Sometimes the cause is noise or light. Perhaps we are too warm. Or pressure points and an achy back keep us tossing and turning. About a third of us wake up to catch another breath because of sleep apnea and hypopnea.

Sleep apnea is stopping breathing while sleeping (apnea means no breath). Closely related is hypopnea (not enough breath). When someone stops breathing or breathes too shallowly, their blood oxygen level falls (hypoxemia). Normally, the medulla oblongata in the brain stem sends a signal to start breathing, or to move to remove an obstruction. This is why a drowning person may try to fight off a rescuer. They are reflexively desperately trying to breathe.


How are sleep apnea and hypopnea measured?

The two most commonly used ways of describing and measuring obstructive sleep apnea are the Apnea-Hypopnea Index (AHI) and blood oxygen saturation. These are the basis of categorizing the severity of sleep apnea in a patient.


AHI is the average number of episodes of apnea or hypopnea in an hour as counted in a clinical sleep evaluation (polysomnography). If this number is less than 5, it is considered either minimal or no severity. Mild is 5 or more but less than 15. From 15 to just less than 30 is moderate. 30 or more is severe.


Among other things monitored is desaturation (the reduction of oxygen in the blood). Normally the saturation of oxygen is the mid-to-high 90s (96-98%). Classification of desaturation severity is not generally uniform, but in the low 90s (85-90%) is usually considered mild, from 89% down to 80% moderate, and below 80% severe.


Another measurement used is the RDI (Respiratory Disturbance Index). This is based not only on AHI and desaturation, but includes other factors. Therefore the numbers will differ, mostly on the higher side.


What are the effects of sleep apnea and hypopnea?

Deep sleep depends on the body being totally relaxed. When the brains stem says, “Get that next breath,” the person either shifts into light sleep or rouses partly awakened. The interruption of deep sleep often leaves a person groggy. If they get up, they may walk like a drunk.


This also has consequences through the day. Interrupted sleep often results in excessive daytime sleepiness (hypersomnolence)–dangerous when driving–as well as inattention and irritability. It may also contribute to unwise eating behavior, which has its own consequences, such as obesity and diabetes.


Lack of proper rest due to sleep apnea contributes to several health problems. Since sleep cycles are used by the body to rebuild stressed and damaged tissues, such as building muscle mass after exercise and healing cuts, burns, etc., sleep deprivation can slow down healing and building strength.

Circulatory disease

Some of the observable effects include circulatory disease. It also affects long-term and short-term memory negatively. And a study by the Pritzker School of Medicine at the University of Chicago showed that sleep deprivation contributes to hormonal imbalance.


One obvious effect of obstructive sleep apnea is snoring . This can have a negative impact on family relations.

Obstructive Sleep Apnea, an In-Depth Patient Education Report by the University of Maryland Medical Center, describes several other effects of OSA.


Who has sleep apnea and hypopnea?

According to a research report published in the New England Journal of Medicine (Young, Palta, Dempsey 1993), men were 2.0 to 3.7 times as likely as women to have sleep-disordered breathing in the 30-39 age group. The ratio differs by age group, narrowing for older adults. Other studies differ in the actual numbers, but they still show that men are significantly more likely than women to have Obstructive Sleep Apnea.

According to a report by the Alaska Sleep Education Center, while women are half as likely as men to have obstructed sleep apnea, eight times as many men as women are diagnosed with this disorder. The Center concludes that sleep apnea in women is often under-diagnosed, with their symptoms misdiagnosed as something else.


What causes sleep apnea and hypopnea?

There are three kinds of sleep apnea, classified by the cause:

    • Obstructive Sleep Apnea
    • Central Sleep Apnea
    • Mixed Type Sleep Apnea

Obstructive Sleep Apnea (OSA)

OSA is caused by some kind of obstruction of the airway. This is usually temporary, since the person will rouse and move in a way that relieves the obstruction. Some of the more commons types of obstruction are nasal (in the nose), pharyngeal (in the throat), and hypophar (the base of the tongue).


If breathing is obstructed in the nose, breathing is usually transferred to the mouth.


Pharyngeal OSA is frequently caused by the swelling or excess relaxation of certain tissues. Notable are the tonsils, the adenoids and the uvula. In obese persons, fatty tissues in the sides and front of the neck can impinge on the throat, closing it when the subject falls asleep.

Over-relaxation of muscles

When mouth and throat tissues are overly relaxed, where they fall is determined by the position of the body, head and neck. If they fall so they block the airway, the result is apnea or hypopnea.  This is more common in the supine position (lying flat on the back), and least common in the prone position (lying on the stomach). It is also less likely when the head is sufficiently elevated.

Central Sleep Apnea (CSA)

The medulla oblongata is where primitive functions are regulated. This includes heart rate, digestion, bladder and bowel control, and breathing. In a condition called Cheyne-Stokes Respiration, the respiratory control center (RCC) in the medulla fails to sends the signals for inhalation and/or exhalation.

Developmental and genetic factors

One cause of CSA is developmental or genetic, where the RCC does not operate normally because of a genetic defect or abnormal development. Sometimes this can be controlled by medication.

Disease factor

Disease is another possible cause of CSA, especially spinal meningitis (Schmidt, Cohrs, Heinemann, Goerdt, Djukic, Heimann, Wallesch, Nau).

Incidental factors

Another cause is incidental, the effect of alcohol, prescription or over-the-counter medications, or illicit drugs. Environmental toxins can also be a cause, and chemical flame retardants are suspected by some critics.

Mixed Type Sleep Apnea (MSA)

MSA is a combination of OSA and CSA in the same episode. It usually begins with obstruction, but the RCC does not signal the body to rouse and move to remove or bypass the obstruction. One example would be not switching to mouth breathing when nasal passages are obstructed. If hypoxia continues for too long, the RCC itself may be negatively affected, not responding quickly enough to prevent permanent damage.


What are other contributing factors?

Besides actual causes, other contributing factors can facilitate or trigger episodes of apnea and hypopnea during sleep.  Some are permanent or long-lasting, such as asthma and non-seasonal allergies. Short-term cautions include, among other things, seasonal allergies, air-borne particles (e.g. smoke and dust), and illnesses (e.g. colds and sinus infections).

Alcohol and Drugs

Alcohol and some medicines also play a role in triggering OSA episodes or making them worse. They relax the muscles in the throat beyond the normal relaxation of rest and sleep. They also have a role in CSA, since they can affect the central nervous system, including the medulla oblongata. In this case, it takes a greater degree of hypoxia to trigger a breath-taking response.


Among behavioral factors is the subject’s sleeping position. Generally, OSA episodes are more likely with back sleeping than with side sleeping.  For those sleeping on their backs, the elevation of the head makes sleep apnea more or less likely.


Possible material factors may include beds and mattresses, since they influence a patient’s sleeping position. When the body relaxes, including mouth and throat muscles, the position of the head and neck determines which way they collapse if they are overly relaxed. When lying flat on one’s back, collapsed tissues are more likely to block the airway, cutting off breath. This is why some OSA sufferers sleep in recliners rather than in bed.


How is Sleep Apnea Treated?

There are several means of treating sleep apnea and hypopnea. The treatment depends on the particular cause and the severity of the disorder. A treatment is more effective when addressing the specific cause of the apnea and the triggers of the episodes.


The most common treatment for obstructive sleep apnea is Continuous Positive Airway Pressure (CPAP). The patient is equipped with a mask or nostril tubes which provide a flow of air at a mild pressure to force more air past obstructions and down into the lungs. Depending on the patient and the physician’s prescription, other things may be added to the air, such as oxygen or humidity. The pressure must be low enough to not block exhalation.

Dental Appliance

For some OSA patients, a dental appliance can hold the tongue and/or soft palate in place while they sleep, keeping the airway open. Usually the appliance pulls the jaw forward, which also pulls the tongue forward to keep it from blocking the pharynx.


For some patients, surgery is used to remove or restructure nose, mouth and throat tissues to prevent obstruction. This may involve tonsils, adenoids, the soft palate, the tongue, the uvula, sinuses, and the nasal septum, as well as other tissues which get in the way of breathing.

Behavioral Modification

Behavioral modification is a form of treatment in which the patient can change contributing factors without special procedures or devices. A few of these are side sleeping, elevating the upper body for sleep, losing weight, regular exercise to increase muscle tone, and avoiding certain foods, beverages or activities leading up to bedtime.

Side Sleeping

Side sleeping helps in two ways. First, it keeps tissues of the mouth, soft palate, and throat–especially the tongue–from falling into the airway (British Snoring & Sleep Apnoea Association). Also, the lung can expand more fully then when sleeping on one’s back (Joosten, Edwards, Wellman, Turton, Skuza, Berger, Hamilton).

Stomach Sleeping

Another solution, sleeping on one’s stomach, has its own problems. First, this position is hard on the lower back for many persons. Then, the sleeper has to position the head so as to not suffocate. This usually means turning the head to one side, which may cause problems with the neck. A body pillow can help by holding the body higher so that, with support for the forehead, the person can sleep face down with the nose and mouth free. Several body pillows are on the market, such as the Body Pillow By Snuggle-Pedic, which is top-rated on Amazon.


How do memory foam mattresses help with sleep apnea and hypopnea?

How does a mattress influence someone’s sleeping position? If a mattress is too firm, it is uncomfortable for side sleeping. Too much pressure is put on the hips, shoulders and knees. And an unsuitable pillow can distort the neck. At the same time, the lumbar sags to one side, leaving the sleeper with a back ache. So the sleeper with OSA sleeps on their back, and has episodes of apnea and hypopnea.  How can this be helped?


Softness is not enough

The subject can get a softer mattress, but it might not provide adequate support. Just being soft is not good enough. Better is a mattress which conforms its support so that the whole body is supported, resulting in good spinal posture with no pressure points. Three kinds of mattresses meet this requirement, memory foam (visco-elastic), latex and pocket coils. All three conform to the sleeper’s body.

Effectiveness of memory foam

Of these three, a memory foam mattress conforms most closely, especially when the top layer is memory foam. Research by Leilnahari, Fatouraee, Khodalotfi, Sadeghein, and Kashani confirmed that visco-elastic foam yielded the best spinal support. A mattress which properly supports the spine during side sleeping is more likely to help lungs to open fully.

Underlying support

Spinal support also depends on firmer underlying support. The original Tempur-Pedic design was a layer of memory foam atop a very firm polyurethane foam base layer. However, as Dr. Rick Swartzburg found out, it was still too firm to be suitable for side-sleeping. He designed the Tri-Pedic with two memory foam layers of different densities. A top layer of memory foam can also be combined with a middle layer of latex, as in the Soft-Pedic.

Pillows, too

A good pillow can keep the head comfortable and the neck in line with the spine for both side-sleepers and back-sleepers. A study published in the Journal of Physical Therapy Science concluded that contoured pillows best supported the neck: “Pillows with uniform heights are not suitable for a supine or side-lying position. In the case of both positions, users should be allowed to select pillows in shapes that can support the neck” (Her, Ko, Woo, Choi). Among the best are shredded memory foam pillows. A top-rated one is the Snuggle-Pedic. Closely following shredded memory foam are shredded latex pillows.


Even with a good memory foam mattress suitable for sleeping on one’s side, some OSA subjects may still prefer sleeping on their backs. For them, wedges can elevate the upper body to a position where sleep apnea episodes are not triggered, which also stops snoring. But if the wedge does not work, it cannot be readily adjusted. Adjustable beds can be adjusted until they reach the no-snore/no-apnea position.


The sleep disorders sleep apnea and hypopnea are real problems which can adversely affect one’s health, daily activities and relationships. They can be diagnosed and treated, especially by a sleep specialist or a physician trained in the area of sleep disorders.


Where can I find out more?

Here are several online resources about sleep apnea: