Sleep Apnea & Heart Rate

Sleep apnea and heart rate are closely connected. During a normal night of sleep, heart rate decreases and becomes more stable as the body rests and recovers. In people with sleep apnea, this normal pattern is disrupted by repeated breathing pauses (apneas) and reduced breathing (hypopneas).

Here is what happens during a sleep apnea event:

• Airway collapse: The airway narrows or closes during sleep, reducing or stopping airflow.
• Oxygen drop: Blood oxygen levels begin to decrease as breathing pauses continue.
• Stress response: The body's nervous system activates a 'fight or flight' response, releasing stress hormones that increase heart rate and blood pressure.
• Arousal: The brain partially awakens to restore breathing, often causing a brief heart rate spike before settling back.
• Cycle repeats: This cycle can occur dozens of times per hour in severe sleep apnea, repeatedly stressing the cardiovascular system.

Over time, these repeated stress cycles can contribute to cardiovascular problems, including high blood pressure, heart disease, and arrhythmias. Learn more about the health risks of untreated sleep apnea.

Resting heart rate during sleep is an important cardiovascular metric. For most adults, a normal resting heart rate during sleep ranges from 50 to 70 beats per minute, though individual variation is common. Heart rate typically reaches its lowest point during deep sleep and is more variable during REM sleep.

Many wearable devices track overnight resting heart rate and provide trends over time. In people with sleep apnea, resting heart rate during sleep may be elevated compared to normal, because the repeated breathing pauses and arousals prevent the heart from fully settling into a low, stable rhythm.

However, an elevated resting heart rate can also be caused by many other factors — including stress, caffeine, alcohol, medications, poor physical fitness, thyroid conditions, and other medical conditions. If your wearable consistently shows elevated overnight heart rate, it is worth discussing with a healthcare provider, especially if you have other symptoms.

In addition to resting heart rate, the pattern of heart rate throughout the night can provide useful information. A healthy overnight heart rate graph typically shows a gradual decline as you fall into deeper sleep, with some variation during REM sleep and brief increases during natural awakenings.

In people with sleep apnea, the overnight heart rate graph may show:

• Frequent spikes: Heart rate may spike repeatedly throughout the night, corresponding to breathing pauses and arousals.
• Elevated baseline: The overall heart rate may remain higher than expected, as the cardiovascular system is repeatedly activated.
• Reduced heart rate variability: The normal variation in heart rate that accompanies healthy sleep stages may be blunted.
• Irregular patterns: Heart rate may show erratic fluctuations rather than the smooth, gradual changes seen in healthy sleep.

These patterns are not definitive — they can also be caused by other conditions and lifestyle factors. But if you notice them consistently, particularly alongside sleep apnea symptoms, a professional sleep evaluation is warranted.

Oxygen saturation and heart rate are closely linked. When blood oxygen levels drop (a condition called hypoxia), the heart must work harder to deliver oxygen to the body's tissues. This causes heart rate to increase.

In sleep apnea, oxygen levels can drop repeatedly throughout the night — sometimes to concerning levels. Each oxygen drop triggers a heart rate increase as the cardiovascular system compensates. This is why some people with sleep apnea show a correlation between oxygen variation and heart rate spikes on their wearable devices.

Clinical sleep tests measure oxygen saturation continuously using a calibrated fingertip pulse oximeter, which is far more accurate than consumer wearable oxygen estimates. The clinical data allows a physician to see exactly how often and how severely oxygen levels drop, and how the heart responds. Learn more about sleep apnea and low oxygen.

Sleep apnea is associated with an increased risk of arrhythmias — irregular heart rhythms. The most common association is with atrial fibrillation (AFib), a rapid and irregular heartbeat originating in the upper chambers of the heart. Research has shown that people with sleep apnea are significantly more likely to develop AFib than those without.

The mechanism is related to the repeated stress on the heart. Oxygen drops, pressure changes in the chest, and activation of the nervous system during apnea events can affect the heart's electrical system, creating conditions that favor arrhythmias.

Some smartwatches offer ECG features that can detect certain arrhythmias, including AFib. While this is a useful screening tool, it is not a diagnostic device. If an irregular rhythm is detected, you should see a physician for a comprehensive evaluation. Learn more about the connection between sleep apnea and atrial fibrillation.

Heart rate monitoring during sleep can serve as an early warning system. While it cannot diagnose sleep apnea, it can highlight patterns that warrant further investigation. The combination of elevated heart rate, oxygen variation, and poor sleep quality on a wearable device — especially when accompanied by symptoms like snoring and daytime fatigue — is a strong signal to seek professional evaluation.

If sleep apnea is diagnosed, effective treatment can help normalize heart rate patterns and reduce cardiovascular stress. Treatment options include oral appliance therapy for patients who prefer a non-CPAP approach. The first step is a sleep evaluation to confirm whether sleep apnea is present.

It is also important to remember that heart health and sleep health are interconnected. If you have concerns about your heart rate patterns, discuss them with your healthcare provider. They can determine whether a sleep evaluation, cardiac evaluation, or both is appropriate.