Obesity and Obstructive Sleep Apnea

Obesity, usually assessed through the body mass index (BMI), is a recognized cause of obstructive sleep apnea (OSA).  Obstructive sleep apnea syndrome (OSAS) is currently a clinically defined syndrome associating excessive tiredness (somnolence) and one or two of the following symptoms: severe snoring, nocturnal respiratory arrest, repeated nocturnal awakening, non-recuperative sleep, diurnal fatigue, and altered concentration.  Obstructive sleep apnea syndrome (OSAS)  is characterized by recurrent episodes of upper airway collapse and obstruction during sleep.

In obese patients, obstructive sleep apnea syndrome (OSAS) is attributed to a reduction in throat-size because of fat deposition around the throat. The effect of weight loss on the size of the upper airways of obese subjects is implied however not absolute. The reason for this is that up to 30% of patients with significant clinical sleep apnea entitled to CPAP treatment have a BMI lower than 30 kg/m2, the usual limit between overweight and obesity. This points out that there are other factors that cause obstructive sleep apnea other than fat deposits around the throat.

It remains nevertheless true that BMI and sleep apnea severity show a dose-response relationship; the prevalence of OSA among the severely obese has been reported to range from 50% to 90%, leading to the assumption that effective treatment of obesity could cure OSA. Studies have shown that a weight reduction of about 15% of baseline body weight may substantially increase the pharyngeal cross-sectional area and substantially improve the severity of OSAS in morbidly obese subjects with sleep apnea.

What is Sleep Apnea?

Sleep apnea is a breathing disorder in which the breathing of the asleep individual either stops for a period or becomes labored. Typically, it is termed sleep apnea if the breathing ceases for ten seconds and more or the breath intake is less than 25% of a normal breath. The condition is usually found in adults, it is not so common with children.

The pauses in breathing or shallow breaths can last from a few seconds to a few minutes. The resumption of normal breathing is often accompanied by a snort or a choking sound. Sleep apnea can remain undetected for a long time, even years. This is because the subject is usually unaware of the problem as he is sleeping. There are no conclusive blood tests to detect the condition. So, if you visit a doctor to remedy fatigue and sleepiness during daytime, the doctor is more likely to consider other potential causes.

Sleep apnea can be a causative factor in introducing or worsening conditions such as high blood pressure, congestive heart failure, and mood disorders.

Types of sleep apnea

The condition is characterized by three different types –

1. Central sleep apnea

2. Obstructive sleep apnea

3. Mixed sleep apnea

In central sleep apnea (CSA), the brain falters in sending neurological signals to the respiratory muscles so that these may execute inhalation and exhalation in a timely manner. The evenness of the respiration rate is affected by the inability of the brain's respiratory control centers to respond to the increasing carbon dioxide levels in the blood stream. CSA is often present in individuals, infants included, that have a prevalent heart condition or are on certain medication. The condition can manifest itself even when the subject is awake, but it takes on more serious dimensions if it occurs when the person is sleeping.

People suffering from coronary heart disease may experience angina pains or even a heart attack because of the low levels of oxygen in the blood. Poorly oxygenated blood can trigger sudden seizures even in individuals that do not suffer from epilepsy. Obstructive sleep apnea (OSA) is characterized by the breathing passage becoming obstructed, an unsuccessful attempt at breathing, a drop in oxygen levels, and resumption of breathing during which the subject may gasp for air.

The flow of air may be obstructed if the septum, which separates the two nostrils, is deviated to one or both sides. Poor muscle tone, particularly in obese individuals, can cause the soft tissue at the level of the throat to collapse. The condition is more common in men. Overweight individuals, smokers, aged persons, and diabetics are at increased risk from this condition. Symptoms include snoring, restlessness during sleep, and lethargy during the following day.

The sleeping phase is a period during which the heart can rest and beat at a steady rhythm; however in cases of OSA, the plummeting oxygen levels result in the heart having to pump harder. Blood vessels constrict in order to direct the flow of blood to the brain and vital organs. The constriction results in an increase in blood pressure. OSA is a known risk factor for heart disease and hypertension. It can worsen the already existing condition in patients. In several cases it has been noted that treating OSA can decrease blood pressure and gradually bring it back to normal.

In mixed apnea, the subject experiences episodes of both OSA and CSA. It is often witnessed in people that have a long-standing history of OSA.

Causes of sleep apnea?

The collapse of the soft tissue around the throat that leads to sleep apnea can be caused by a number of reasons; these include obesity, acid reflux, and disorders in the central nervous system.

There is general consensus in the medical fraternity that carrying around excessive weight can lead to obstructive sleep apnea. A very high percentage of those suffering from sleep apnea are obese. Abdominal and upper body obesity are considered significant risk factors. Also, there is evidence to suggest that sleep apnea patients often end up gaining weight which in turn worsens their condition. Both obesity and sleep apnea are linked to hypertension and an increased workload for the heart; it is important that obese individuals undergo treatment for weight reduction. This will not only help control the sleep apnea problem but also aid in treating high blood pressure and diabetes.

Obesity hypoventilation syndrome is a condition similar to sleep apnea; subjects fail to breathe rhythmically and deeply enough to ensure that the oxygen levels in the blood remain high. People with this condition also experience sleep apnea during the night. CPAP is considered an effective treatment for this syndrome.

Although the exact relationship between asthma and sleep apnea is not clearly established, there is evidence to suggest that a spasming airway can collapse during a bout of asthma.

A person with a smaller windpipe that is easier to obstruct is at greater risk of sleep apnea. Inflamed tonsils can also block the air passage and are a common cause of sleep apnea in children.

Lifestyle-related causes include smoking and alcohol consumption. Certain medications can relax the muscles in the air passage causing them to collapse when the subject is asleep.

Diagnosis of sleep apnea

Sleep apnea is diagnosed through a sleep study test known as polysomnography. It is a painless test in which sensors connected to the asleep patient record brain and muscle activity, eye movement, breathing pattern, heart rate, oxygenation levels of blood, and oxygen flow to and from the lungs. The test is useful in detecting mid-level to severe cases of sleep apnea. It cannot be relied upon for mild cases of OSA. In the absence of established fixed criteria, the clinician has to focus on an individual's history as deduced from signs and symptoms observed by the patient.

Oximetry is a screening methodology that monitors and records blood oxygen levels in sleeping subjects. Abnormal results can point to sleep apnea and the doctor may recommend polysomnography to confirm the diagnosis.

Treatment of sleep apnea

Sleep apnea can be treated non-surgically with the help of therapies or through surgeries to remove the excessive soft tissue that may be blocking the upper air passages.

Continuous positive airway pressure (CPAP) therapy uses a machine to deliver pressurized air via a mask on the nose. The air pressure is just enough to keep the air passages open and stop the soft tissue from collapsing. This therapy has gained wide acceptance; although it may take some time to adjust to the strapped-on mask. The pressure settings on the CPAP machine change with the subject's weight.

An alternative to CPAP is BiPAP, which stands for bi-level positive airway pressure. The air pressure adjusts automatically while the subject sleeps. The pressure increases during inhalation and falls when exhaling. Adaptive servo ventilation (ASV) is an even more advanced therapy in which the apparatus stores information on the subject's breathing pattern and uses it to ensure a normal breathing pattern without any pauses.

Weight loss and its positive effect on sleep apnea

Weight loss is a commonly recommend treatment for sleep apnea patients. Weight loss through dieting and lifestyle changes benefits subjects. If surgery is recommended then bariatric surgery should be considered as it leads to sustained weight loss. Post bariatric surgery patients have reported improvements in their sleep apnea condition. Preoperative and postoperative evaluation of patients leaves little doubt that this form of surgery is highly beneficial as it results in significant improvement and indeed in some cases completely curing sleep apnea. It is recommended that CPAP therapy be continued for about six months after the surgery. After 12 months, the situation can be reassessed to determine if CPAP therapy needs to be continued.

Obstructive sleep apnea is a sleep disorder with symptoms of loud snoring and long pauses in breathing. Often the person with obstructive sleep apnea is unaware of their condition until they’re told by a family member or friend.

Obstructive sleep apnea is linked to several serious conditions and experiences.

Needless to say, the decrease in general health risks in these patients as a result of bariatric surgery is obvious. The safest recommendation however would be that patients who undergo bariatric surgery should perhaps be advised to continue CPAP therapy until a new evaluation is performed at follow-up before deciding to stop treatment.