Adjust Apple Watch settings for 'low heart rate'

My resting heart rate when awake and walking heart rates are pretty low but okay. When I sleep, however, the rate often goes to 38-40 and I get a notification that awakens me. (4 times last night). The default for the watch is a heart rate below 40 is a 'low heart rate'. Is there a way to change this setting? I would sleep better is I could change the setting to 'below 38'.