I own an Apple watch series 2 and I've recorded my heart rate during sleep for a week now. Twice during this period my heart rate during sleep shot up to around 110 for 1.5 to 2 hours and that seems very suspicious to me. Since I don't have any sleep problems (that i know of) I was wondering whether this was an inaccuracy of the heart rate sensor. So I wanted to know whether there is some consistent way to trick the sensor into recording double the actual heart rate (e.g. by pressing the watch against the wrist or something).

2 Answers 2


If you are concerned, you need to see a doctor.

That being said, dreaming and nightmares during normal REM sleep increase your blood pressure and heart rate. REM sleep lasts, on average, for about 20% of your total sleep time.

To calibrate your watch, you could always purchase a relatively inexpensive heart rate monitor to see if both devices sense the increase, and how accurate they are in comparison.


I have not heard of cases where the Apple Watch consistently records the double actual hearts for hours on end. If I were you, I would use a different type of device to measure your heart rate to ensure that you are actually seeing bad readings and not some kind of health problem.

Apple has a support page with tips on how to get the most accurate heart rate measurements:


In my own experience the most important is ensuring a good fit on the wrist. If you can easily get the watch too "loose" when moving around in bed, consider using a different kind of strap.

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