Sleep apnea is a common and serious disorder in which breathing repeatedly stops for 10 seconds or more during sleep. The disorder results in less oxygen in the blood and can briefly awaken sleepers throughout the night.
The two main types of sleep apnea are obstructive sleep apnea and central sleep apnea.
Obstructive sleep apnea, or OSA, happens when there’s a problem with the mechanics of your breathing. Central sleep apnea, or CSA, happens, not because of a mechanical problem, but because your brain doesn’t signal your muscles in the right way. That causes you to stop breathing briefly or to breathe so lightly that you don’t get enough oxygen.
Causes of Obstructive Sleep Apnea
In adults, the most common cause of obstructive sleep apnea is excess weight and obesity, which is associated with the soft tissue of the mouth and throat. During sleep, when throat and tongue muscles are more relaxed, this soft tissue can cause the airway to become blocked.
More than half of people with obstructive sleep apnea are either overweight (body mass index, or BMI, of 25-29.9) or obese (BMI of 30.0 or above).
A 10% weight gain raises your risk of OSA by six times, though the effect goes down after age 60.
Another marker of obesity is the size of your neck. Men with a neck circumference above 17 inches (43 centimeters) and women with a neck circumference above 15 inches (38 centimeters) have a much higher risk for OSA.
Other possible causes or risk factors for OSA include:
- A narrow throat
- A round head
- Excess growth due to hormones (acromegaly)
- Deviated septum (problem with nose structure)
- Medical conditions that congest upper airways
- Alcohol or drug abuse
In children, causes of obstructive sleep apnea often include enlarged tonsils or adenoids and dental conditions such as a large overbite. Less common causes include a tumor or growth in the airway, and birth defects such as Down syndrome and Pierre-Robin syndrome. Down syndrome causes enlargement of the tongue, adenoids, and tonsils, and there is less muscle tone in the upper airway. Those who have Pierre-Robin syndrome have a small lower jaw, and the tongue tends to ball up and fall to the back of the throat. Although childhood obesity may cause obstructive sleep apnea, it's much less commonly linked to the condition than adult obesity.
Regardless of age, untreated obstructive sleep apnea can lead to serious complications, including cardiovascular disease, accidents, and premature death. So it's important that anyone with signs and symptoms of obstructive sleep apnea -- especially loud snoring and repeated nighttime awakenings followed by excessive daytime sleepiness -- get the right kind of medical evaluation.
Causes of Central Sleep Apnea
In many cases, doctors cannot figure out the root cause of CSA. Doctors call this primary, or “idiopathic,” CSA.
But some CSA is linked to another illness, a medication, or your environment:
- Stroke, heart failure, or kidney failure can cause CSA with a distinctive Cheyne-Stokes breathing pattern. Doctors call this CSB-CSA.
- Heart conditions, kidney problems, and other illnesses can also cause non-CSB CSA.
- High-altitude CSA typically happens during sleep when you’re very high up (above 15,000 feet). It usually goes away when you return to lower altitudes.
- Some medications and drugs, especially opiates like hydrocodone or fentanyl, can cause CSA. Your doctor may be able to help you adjust your medication. Talk to a doctor or therapist if you think you may be misusing medications, especially opiates.
In children, the reason for CSA is typically unclear (idiopathic).
Still, there are a number of things that can interfere with the brain signals that normally help your child breathe. And these could lead to CSA:
- Premature birth
- Smoking during pregnancy
- Brain tumors
- Cerebral palsy
- Head injury
- Problems at the base of the skull, or brain stem
Sleep Apnea Demographics
About 4%-9% of middle-aged adults are thought to have obstructive sleep apnea, although the condition is often undiagnosed and untreated. Among people over age 65, it's estimated that at least 10% have the condition. Aging affects the brain's ability to keep upper airway throat muscles stiff during sleep, increasing the chance that the airway will narrow or collapse.
Obstructive sleep apnea is up to four times as common in men as in women, but women are more likely to have sleep apnea during pregnancy and after menopause. In older adults, the gender gap narrows after women reach menopause.
Postmenopausal women who receive hormone replacement therapy are significantly less likely than those who don't to have obstructive sleep apnea, suggesting that progesterone and/or estrogen may be protective. But hormone replacement therapy is not considered to be an appropriate therapy for the condition, because it can affect health in other ways.
Other things associated with obstructive sleep apnea include:
- Family history. About 25%-40% of people with obstructive sleep apnea have family members with the condition, which may reflect an inherited tendency toward body problems.
- Ethnicity. Sleep apnea also is more common in African Americans, Hispanics, and Pacific Islanders than in whites.
Sleep Apnea Complications
Increasing evidence links sleep apnea to conditions such as high blood pressure (hypertension), stroke, heart attack, diabetes, gastroesophageal reflux disease, nocturnal angina, heart failure, hypothyroidism, and an abnormal heart rhythm. About half of sleep apnea patients have hypertension, and untreated sleep apnea increases the risk of heart-related illness and death.
In addition, sleep apnea is linked to excessive daytime sleepiness, which increases the risk for motor vehicle accidents and depression.
Some complications may be related to the release of stress hormones, which may be triggered by frequent decreases in blood oxygen levels and reduced sleep quality. Stress hormones can increase heart rate and also can lead to the development or worsening of heart failure.
Medical treatment -- which includes control of risk factors, use of continuous positive airway pressure (CPAP) or oral appliances, and surgery -- may improve signs and symptoms of obstructive sleep apnea and its complications. In the case of central sleep apnea, doctors will also address any medical condition that might be a cause.