This type of sleep apnea happens when the muscles in the back of the throat relax. These muscles support the soft palate, the triangular piece of tissue hanging from the soft palate called the uvula, the tonsils, the side walls of the throat and the tongue.When the muscles relax, your airway narrows or closes as you breathe in. You can't get enough air, which can lower the oxygen level in your blood. Your brain senses that you can't breathe, and briefly wakes you so that you can reopen your airway. This awakening is usually so brief that you don't remember it.You might snort, choke or gasp. This pattern can repeat itself 5 to 30 times or more each hour, all night. This makes it hard to reach the deep, restful phases of sleep.

Factors that increase the risk of this form of sleep apnea include:

• Excess weight. Obesity greatly increases the risk of OSA. Fat deposits around your upper airway can obstruct your breathing.

• Neck circumference. People with thicker necks might have narrower airways.
  
• Being male. Men are 2 to 3 times more likely to have sleep apnea than are women.
• Being male. Men are 2 to 3 times more likely to have sleep apnea than are women.
• Being older. Sleep apnea occurs significantly more often in older adults.
• Smoking. Smokers are three times more likely to have obstructive sleep apnea than are people who've never smoked. Smoking can increase the amount of inflammation and fluid retention in the upper airway.
• Family history. Having family members with sleep apnea might increase your risk.
• Use of alcohol, sedatives or tranquilizers. These substances relax the muscles in your throat, which can worsen obstructive sleep apnea.
• Nasal congestion. If you have trouble breathing through your nose — whether from an anatomical problem or allergies — you're more likely to develop obstructive sleep apnea.
• Medical conditions. Congestive heart failure, high blood pressure and type 2 diabetes are some of the conditions that may increase the risk of obstructive sleep apnea. Polycystic ovary syndrome, hormonal disorders, prior stroke and chronic lung diseases such as asthma also can increase risk.

Central sleep apnea

This less common form of sleep apnea occurs when your brain fails to send signals to your breathing muscles. This means that you make no effort to breathe for a short period. You might awaken with shortness of breath or have a difficult time getting to sleep or staying asleep.

Risk Factors

• Being older. Middle-aged and older people have a higher risk of central sleep apnea.

• Being male. Central sleep apnea is more common in men than it is in women.
  
• Heart disorders. Having congestive heart failure increases the risk.
• Being male. Men are 2 to 3 times more likely to have sleep apnea than are women.
• Using narcotic pain medicines. Opioid medicines, especially long-acting ones such as methadone, increase the risk of central sleep apnea.
• Stroke. Having had a stroke increases the risk of central sleep apnea.

Complications

• Fatigue. The repeated awakening associated with sleep apnea makes typical, restorative sleep impossible. People with central sleep apnea often have severe fatigue, daytime drowsiness and irritability. You might have difficulty concentrating and find yourself falling asleep at work, while watching television or even while driving.

• Cardiovascular problems. Sudden drops in blood oxygen levels that occur during central sleep apnea can adversely affect heart health.If there's underlying heart disease, these repeated multiple episodes of low blood oxygen — known as hypoxia or hypoxemia — worsen prognosis and increase the risk of irregular heart rhythms.