Fast Heart Rate While Sleeping: Is It Sleep Apnea?

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Smart watches and sleep tracking rings have made it easier than ever to monitor what happens while we sleep. So seeing an unusually high heart rate on your morning sleep report can understandably be worrying. You may also find yourself waking up with a racing heart, feeling your heart beating faster than usual or even experiencing occasional nighttime palpitations.

A fast heart rate while sleeping can have many possible causes, such as stress, anxiety, alcohol and illness. Even eating a large meal close to bedtime can affect your sleeping heart rate. 

However, if your heart rate regularly changes throughout the night or you often wake up with your heart racing, it is important that you speak to your doctor. One possible cause is obstructive sleep apnea, OSA, a common yet serious sleep disorder that can have a negative impact on your breathing and cardiovascular health.

What is a Normal Sleeping Heart Rate?

To understand when your heart rate is too fast, you first need to know what a healthy resting baseline looks like.

During the day, a normal adult resting heart rate typically sits between 60 and 100 beats per minute (bpm). When you fall asleep, your body enters a state of deep relaxation. Your metabolism slows down, your blood pressure drops, and your parasympathetic nervous system takes over.

For most healthy adults, heart rate drops by 10% to 20% during sleep. It is completely normal for a sleeping heart rate to dip into the 50s, or even the 40s if you are physically fit and healthy. A heart rate is generally considered "fast" during sleep if it consistently stays above 90 to 100 bpm, or if you see a "rollercoaster" pattern of sudden, dramatic spikes, jumping from a low baseline up to 100+ bpm, multiple times throughout the night.

Rather than focusing on one particular number, it is often more useful to look at your usual pattern. If your sleeping heart rate is consistently high it is important to speak to your doctor. It is also important to remember that smart watches and fitness trackers are not medical diagnostic devices. Their readings are useful for spotting changes or patterns however, they cannot determine whether you have sleep apnea or another medical condition. 

How Sleep Apnea Causes a Racing Heart

OSA occurs when the muscles in the back of your throat relax too much during sleep, causing your airway to collapse. This physical blockage prevents oxygen from reaching your lungs, forcing you to stop breathing for 10 to 30 seconds (or longer) multiple times per hour.

This repeated suffocation places immense physical stress on your cardiovascular system. Here is the biological chain reaction that makes your heart race:

  1. Oxygen levels decrease (Hypoxia): As your airway closes, the oxygen levels in your blood begin to drop rapidly.
  2. The brain responds: Your nervous system reacts to the change in breathing and oxygen levels, releasing stress hormones such as adrenaline and epinephrine.
  3. Heart rate increases: The release of stress hormones can cause your heart rate and blood pressure to rise as your body works to restore normal breathing. 
  4. The cycle repeats: Once you start breathing and normally again, your heart rate may settle before another breathing disturbance occurs.

This can create repeated changes in heart rate throughout the night. Someone with untreated sleep apnea may therefore experience noticeable fluctuations rather than simply having a consistently high heart rate. 

Other Common Causes of a High Nighttime Heart Rate

While sleep apnea is a leading physical cause of a racing heart at night, it is not the only possibility. Other common triggers include:

  • Stress and Anxiety: Chronic stress, panic attacks, or intense nightmares can trigger a "fight or flight" response during REM sleep, causing your heart rate to increase.
  • Alcohol Consumption: Alcohol acts as a sedative initially, but causes a rebound effect as it wears off in the middle of the night, triggering adrenaline spikes and a rapid heart rate.
  • Late, Heavy Meals: Eating a large meal right before bed forces your digestive system to work harder while you sleep, which requires increased blood flow and a faster heart rate.
  • Fever or Illness: When your body is fighting an infection, your heart pumps faster to circulate white blood cells around the body.

If your heart rate is repeatedly higher than usual without an obvious explanation, your doctor can help determine whether investigation is required.

The Cardiovascular Risks of Untreated Sleep Apnea

Occasional changes in heart rate are not necessarily a cause for concern. However, untreated sleep apnea can put repeated strain on your cardiovascular system. Changes in breathing, oxygen levels, heart rate and blood pressure can occur repeatedly throughout the night and over time this can increase the risk of several cardiovascular diseases, including:

  • Resistant Hypertension (High Blood Pressure): The release of stress hormones during episodes of apnea, can result in elevated blood pressure levels throughout the night. 
  • Arrhythmias (like AFib): The added stress on the heart's electrical system increases the risk of atrial fibrillation, an irregular heartbeat that can cause blood clots.
  • Heart Attack and Stroke: The oxidative stress caused by low oxygen levels can damage the lining of your blood vessels, result in plaque buildup and dramatically increase your risk of a stroke or heart attack.

When to See a Doctor

You should not try to diagnose yourself using a fitness tracker alone. However, you should consult a doctor or a sleep specialist immediately if your fast sleeping heart rate is accompanied by:

  • Loud, chronic snoring reported by a bed partner.
  • Waking up gasping, choking, or short of breath.
  • Chronic daytime exhaustion, even after a full night's sleep.
  • Morning headaches or a severely dry mouth.
  • Chest pain, pressure, or a persistent fluttering sensation in your chest.

If sleep apnea seems likely, your healthcare provider may recommend a sleep assessment or sleep study. Depending on your circumstances, this may be performed at home or in a sleep clinic. A sleep study monitors your breathing and takes other measurements while you sleep, to help provide a positive diagnosis or rule out a sleep disorder.

If you are diagnosed with OSA, treatment options such as CPAP therapy can help your air keep your airway open while you sleep. By treating the underlying breathing problem, CPAP can help maintain a healthy resting heart rate and reduce the pressure on your cardiovascular system.

Ready to get to the bottom of your nighttime symptoms? Learn more about comprehensive sleep testing and treatment options at sleepquest.com.