Low Heart Rate Alerts from Your Apple Watch During Sleep

The Apple Watch detected a low heart rate during sleep?

I have been receiving notifications from my smartwatch about low heart rates upon waking up these past couple of days, specifically around 4 AM, with sleep heart rates ranging from 39 to 42 beats per minute for over 10 minutes.
My usual sleep heart rate averages between 40 and 52.
I received a low heart rate notification once before in December 2023, but I hadn't received any since then until recently, when it occurred for two consecutive days.
I'm concerned that there might be an issue with my heart.

Since August of last year, I have been exercising at the gym, doing aerobic workouts on the treadmill 2 to 3 times a week for about half an hour each session, with an average exercise heart rate of around 140 beats per minute.
I'm unsure if the decrease in my sleep heart rate is due to my exercise routine or if it indicates a heart problem.
My regular health check-up reports show slightly elevated total cholesterol and triglycerides, with an A1c of 5.7, but everything else appears normal.
Receiving these notifications has made me quite anxious about my heart health.
I would appreciate any advice from a physician.
Thank you.

Lin, 20~29 year old female. Ask Date: 2024/05/03

Dr. He Dongjin reply Cardiology

Hello, during sleep, the heart rate decreases as the body rests.
This is normal, so there is no need to worry.
Changhua Hospital cares about you.

Reply Date: 2024/05/03

More Info

Receiving low heart rate alerts from your Apple Watch during sleep can understandably cause concern, especially if you notice that your heart rate drops to levels like 39-42 beats per minute (bpm) for extended periods. However, it's essential to understand the context of these readings and what they might mean for your health.

Firstly, it's important to recognize that a low heart rate, or bradycardia, can be a normal physiological response during sleep. When you sleep, your body enters a state of rest and recovery, which often leads to a decrease in heart rate. For many individuals, especially those who are physically active or athletic, a resting heart rate in the range of 40-60 bpm can be typical and not necessarily indicative of a problem. In fact, athletes often have lower resting heart rates due to their enhanced cardiovascular efficiency.

In your case, since you have been engaging in regular aerobic exercise at the gym, it is possible that your heart has adapted to this increased level of fitness, resulting in a lower heart rate during sleep. The average sleep heart rate you mentioned (40-52 bpm) aligns with what might be expected for someone who exercises regularly. However, the alerts you received at 4 AM indicating a heart rate as low as 39 bpm for over 10 minutes could be concerning if they are accompanied by symptoms such as dizziness, fainting, or fatigue.

Your recent health check-up results, which show slightly elevated total cholesterol and triglycerides but normal A1c levels, suggest that while there are some areas to monitor, there are no immediate red flags regarding your heart health. It's also worth noting that the Apple Watch, while a useful tool for monitoring heart rate, is not a medical device and may not always provide accurate readings. Factors such as wrist position, watch fit, and even skin temperature can affect heart rate measurements.

If you continue to receive low heart rate alerts and are experiencing any concerning symptoms, it would be prudent to consult a healthcare professional. They may recommend further evaluation, such as an electrocardiogram (ECG) or a Holter monitor, to assess your heart's rhythm over a more extended period. This can help determine if there are any underlying issues that need to be addressed.

In summary, while low heart rate alerts can be alarming, they are not always indicative of a heart problem, especially in the context of regular exercise. However, if you have concerns or experience symptoms, seeking medical advice is the best course of action. Regular monitoring of your heart health, maintaining a balanced diet, and continuing your exercise routine can all contribute positively to your overall cardiovascular health.

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