Sleep Apnea

Sleep apnea is a condition that causes you to stop breathing while you’re sleeping. The word “apnea” comes from the Greek word for “breathless.” Sleep apnea happens because you stop breathing in your sleep. This happens either because of blockage of your airway (obstructive sleep apnea) or because your brain doesn’t correctly control your breathing (central apnea).

The resulting lack of oxygen activates a survival reflex that wakes you up just enough to resume breathing. While that reflex keeps you alive, it also interrupts your sleep cycle. That prevents restful sleep and can have other effects, including putting stress on your heart that can have potentially deadly consequences.

Who does sleep apnea affect?

Sleep apnea can happen to anyone, ranging from infants and children to older adults. Obstructive sleep apnea is more common in certain circumstances and groups of people:

• Before age 50, it’s more common in people assigned male at birth (AMAB). After age 50, it affects people assigned female at birth (AFAB) at the same rate.
• People are more likely to develop it as they get older.
• Having excess weight or obesity strongly increases the risk of developing it.
• It’s more common in people who are Black, Hispanic or of Asian descent.

Central sleep apnea is most common in certain groups of people:

• People who take opioid pain medications.
• Adults over 60 years old.
• People with heart conditions such as atrial fibrillation or congestive heart failure.
• For some people using CPAP or who have obstructive sleep apnea, this can trigger the development of central events known as treatment-emergent central sleep apnea.
• When people live at high altitudes, this can cause central apneas to occur.

How common is sleep apnea?

Sleep apnea is uncommon but widespread. Experts estimate it affects about 5% to 10% of people worldwide.

How does sleep apnea affect my body?

To understand how sleep apnea works, it helps to know a little bit about the human sleep cycle. Sleep happens in multiple stages:

• Stage 1: Light sleep. This is a short stage that begins right after you fall asleep. It accounts for about 5% of your total sleep time.
• Stage 2: Deeper sleep. This stage is deeper and makes up about 45% to 50% of all the time you spend sleeping (this number goes up as you get older).
• Stage 3: Slow wave sleep. This is the deepest sleep stage, making up about 25% of the time you spend sleeping (this number goes down with age). It’s very hard to wake someone up in stage 3 sleep, and waking up directly from it usually causes “sleep inertia,” a state of “mental fog” and slowed thinking. Parasomnias like sleepwalking and sleeptalking happen in this stage.
• REM sleep: REM stands for “rapid eye movement.” This stage is when you dream. When a person is in REM sleep, you can see their eyes moving beneath their eyelids.

When you fall asleep, you typically enter Stage 1, and then move into and cycle between Stages 2 and 3. After cycling between those stages, you’ll ultimately go into REM sleep and start dreaming. After the first REM cycle, you start a new cycle and go back into Stage 1 or 2. One cycle normally takes about 90 to 110 minutes before another begins. Most people go through four or five cycles per night (assuming they get a full eight hours of sleep).

How sleep apnea disrupts your sleep cycle

Your brain constantly monitors your body’s status and adjusts your heart rate, blood pressure, breathing, etc. Your blood oxygen levels can drop when you stop breathing because of either apnea or hypopnea.

• Apnea: This is when you stop breathing while asleep or have almost no airflow. It combines the Greek roots “a,” which means “not” and “pnea,” which refers to breathing. Combined, it means “breathless.”
• Hypopnea: This combines Greek word roots “hypo” and “pnea.” The root “hypo” means “low” or “under.” Combining these root words means “under-breathing” or “low breathing,” which means you aren’t breathing enough to maintain oxygen levels in your blood.

Your brain reacts to blood oxygen drops — from either apnea or hypopnea — by triggering a failsafe-like reflex, waking you up enough for you to breathe again. Once you resume breathing, your brain automatically tries to resume your sleep cycle.

The more severe your sleep apnea is, the more often you’ll these interruptions happen. The apnea/hypopnea index (AHI) is the average hourly number of apnea or hypopnea events — times when a person stops breathing. The AHI is the main factor determining the severity of sleep apnea. The severity is as follows:

• Mild sleep apnea: This level means a person has an AHI between 5 and 15. That means they have between 5 and 15 apnea or hypopnea events per hour. However, healthcare providers also consider symptoms at this level. If you don’t have other symptoms, they may not consider it severe enough to treat.
• Moderate sleep apnea: People with moderate sleep apnea have between 15 and 29 events per hour. That means a person who sleeps eight hours stops breathing and/or wakes up between 120 and 239 times.
• Severe sleep apnea: People with severe sleep apnea wake up 30 or more times in an hour. That means they stop breathing and/or wake up 240 times or more during a full eight hours of sleep.

Obstructive events, which are very short-lived, can affect any stage of sleep. They’re most common in Stage 1, Stage 2 and REM sleep. That’s why it’s common for people to not remember apnea events, which means they may not know they have a problem until the symptoms are noticeable. Central events are most common in Stages 1 and 2 of sleep but can occur during any stage.