My apple watch showed me a 38-39 bpm alert almost every morning. and today before sleep i got alert again, that i have a heart rate lower than 40 longer than 10 minutes. should i worry? i dont have any other symptoms. thanks

Bradycardia: Heart rates in many young healthy people drop into the 40's or even lower during sleep. Of concern would be persistent rates in the 40's while up and about and inability of the heart rate to accelerate during exercise or symptoms of lightheadedness and fatigue. Nevertheless, a resting baseline EKG is advisable to rule out abnormal bradycardia or sinus node dysfunction. Discuss with your MD.