Is it safe to sleep with apple airpods or any wireless Bluetooth headset?

I listen to books on audible to help me fall asleep. I set the Audible app sleep timer to shut off in 30 minutes. By then I am usually asleep. However the airpods remain in my ear until I wake about 5 hours later. I am wondering if this is safe. Are the airpods Bluetooth active even if not receiving a signal from Audible? Thanks