Sleep Disorders

Obstructive Sleep Apnea (OSA) and Sleep-Disordered Breathing (SDB)

Sleep-disordered breathing (SDB) is a general term for breathing problems that happen during sleep. The various kinds of SDB share two kinds of breathing "events": apneas and hypopneas.

  • apnea: a stop in breathing that lasts ten seconds or longer; a medical term from the greek a-, without, + pnea, breathing = without breathing.
  • hypopnea: a 50% or greater decrease in breathing that lasts ten seconds or longer; a medical term from the greek hypo-, under, + pnea, breathing = under-breathing.

SDB includes three types of sleep apnea-obstructive, central, and mixed-as well as less common disorders like Cheyne-Stokes respiration.

Obstructive sleep apnea (OSA) is the most common type of SDB, affecting approximately 20 million adults. OSA has serious health risks. The good news is that OSA can be easily treated.

Who Has OSA?

Until very recently, doctors thought OSA affected overweight, middle-aged men, but they now know that OSA affects men, women, and children of all body types. One of the reasons this took time to discover is that the symptoms in a young, healthy woman may differ from those of an overweight middle-aged man.

How Common Is OSA?

Estimates for the number of Americans with OSA vary depending on how researchers define it for the study. For instance, one study may count someone with 10 apneas per hour as having OSA while another may consider 15 apneas per hour the minimum for OSA diagnosis. Conservative estimates put the number of adult Americans with OSA between 15 and 20 million.

What Causes OSA?

OSA occurs because of upper airway obstructions (a blocked throat) that can cause snoring and brief interruptions of breathing. Obstructive apneas and hypopneas occur during sleep for two primary reasons: lack of muscle tone and gravity. Excess tissue in the upper airway and physical abnormalities worsen OSA. During sleep, especially in REM sleep, our bodies relax, the muscle tissues like the tongue and soft palate lose their slight rigidity, and the airway collapses.

Normal breathing Obstructive apnea
1. Healthy, open upper airway 2. Obstructed upper airway (yellow arrows indicate attempt to inhale)

 

When these tissues obstruct (block) the upper airway completely, they prevent breathing. They actually begin to suffocate the sleeper. The sleeper wakes up enough to regain control of the upper airway, breathe again, and then fall back to sleep. This happens from dozens to hundreds of times per night for people with OSA, but they usually don't remember waking up.

Each obstruction deprives the body of oxygen and does not allow it to get rid of carbon dioxide that it would normally exhale. When the body sets off "alarms" that it needs more oxygen, the brain wakes the sleeper, breathing resumes, and the individual falls back to sleep until the next obstruction occurs. These obstructions increase heart rate, raise blood pressure, and eventually blunt the body's automatic response system, allowing increasingly more severe apneas and hypopneas to get worse.

These brief wake-ups, called sleep arousals, can cause severe sleep deprivation. Sleep deprivation and its effects are what bring most people with OSA to see their physician. Excessive daytime sleepiness, poor concentration, poor memory, and even depression are common for people with OSA.

Symptoms of OSA

Hypertension and decreased blood oxygen levels are common symptoms for people with sleep apnea, but these are not easily detected. Here are the symptoms that are easiest to identify without diagnostic testing.

  • Excessive sleepiness (use the Epworth Sleepiness Scale to evaluate your sleepiness)
  • Snoring (people with OSA usually snore but not always)
  • Witnessed apneas or irregular breathing during sleep (gasping, long pauses, etc-a spouse or partner may notice these)
  • Difficulty concentrating
  • Memory problems
  • Morning headaches
  • Sexual dysfunction (impotence)
  • Nocturia (getting up to urinate frequently in the night)

Risk Factors for OSA

Physicians have identified a number of factors that may increase a person's risk of having OSA:

  • Obesity
  • Snoring
  • Family history of OSA or snoring
  • Small upper airway (large tongue, large uvula, recessed chin, excess tissue in the throat and/or soft palate).

Heavier people have a greater risk of sleep apnea. In addition, the heavier a person becomes the more severe OSA becomes, so most physicians recommend exercise and a healthy diet for people with OSA.

Researchers have discovered that REM sleep deprivation increases people's appetites and decreases their energy levels. Consequently, researchers believe that OSA might initiate a downward spiral for some people because as they lose sleep, they eat more, gain weight, and increase the severity of their OSA.

Obstructive Sleep Apnea & Your Weight

Obesity is one of the most significant risk factors for obstructive sleep apnea (OSA). While researchers estimate that only 2-4% of the US population suffers from OSA, that number jumps to 20-40% of the obese population. The fact that OSA can cause health problems should be a primary concern for anyone who may have the disease, but overweight people with OSA should understand how this disease makes weight loss more difficult.

Sleepiness & Overeating
Excessive daytime sleepiness, a primary OSA symptom, can contribute to overeating and sedentary behavior. Some people, as a matter of habit, will eat to "wake up" when they feel drowsy during the day. Of course, overeating leads to more weight gain and in turn more severe OSA. Over time, the relationship between excessive daytime sleepiness, overeating, weight gain, and increased sleepiness can become a vicious cycle.

Weight Gain Worsens OSA
The excess adipose tissue (connective tissue consisting mostly of fat cells), which is characteristic of obesity, can contribute to OSA by altering the shape and size of the upper airway. Increased fat deposits narrow the upper airway and increase the likelihood of upper airway obstructions. Sustained weight loss and OSA therapy should be the primary aim for overweight OSA sufferers. For some individuals, OSA therapy contributes to weight loss, as increases in their daytime energy help them become more active. And weight loss helps decrease OSA. In fact, a 10% weight loss can reduce the symptoms of OSA by up to 26%.

Morbid Obesity & OSA
A morbidly obese individual is defined as being more than 100 pounds over their ideal body weight or having a body-mass index [BMI] of 40 or greater. OSA incidence among the morbidly obese is significantly higher than in the general population, 77% compared to 2-4%.

If you are morbidly obese, have OSA, and are thinking about a surgical weight loss procedure, you should learn more about the importance of OSA therapy.

While obesity increases one's risk of developing OSA, OSA affects people of all weights. Also, the correlation between weight and OSA is not as strong among the elderly and in children.

OSA and Surgical Weight Loss Procedures
OSA affects as many as 77% of bariatric surgery candidates. It can have a significant impact on both their pre- and post-operative care. The combination of OSA and bariatric surgery increases the risk of respiratory complications in obese patients.

Surgical Complications of OSA
It is very important for bariatric surgery candidates to be diagnosed and treated for any sleep disorders before weight loss surgery. General anesthesia exacerbates the obstructive symptoms in patients with OSA. Many patients have suffered severe, life-threatening, and sometimes fatal apneas after general anesthesia. Special care and monitoring should be utilized for OSA patients undergoing anesthesia. Continuous positive airway pressure (CPAP) is the most common and effective method for treating OSA, and it is vital for many patients undergoing weight loss surgery. CPAP prevents airway collapses (apneas), thereby preventing the negative effects of OSA.

CPAP Therapy after Bariatric Surgery
As the patient loses weight post-operatively, CPAP therapy must adapt to their changing needs. Pressure requirements will usually change, as insufficient pressure or too much pressure may make therapy uncomfortable, causing the patient to discontinue its use. It is therefore important to choose a technology that responds to these changing needs. Although weight loss induced by bariatric surgery will eliminate OSA in some people, it isn't a guaranteed "cure" for OSA. Because of this, continued OSA monitoring and treatment following surgery is always necessary.

Hypoventilation & Morbid Obesity
OSA is not the only worry for morbidly obese patients. Obesity-related hypoventilation is a condition whereby, due to excessive weight, the muscles of the chest wall and diaphragm don't have the strength to move the thorax and abdomen. Consequently, patients can't adequately ventilate themselves while asleep or while awake. They retain carbon dioxide and suffer extensive sleep disruption.