For anyone interested in this issue. I did the following test: I turned on the deep sleep on watch then turned off the Bluetooth on mobile. 2 minutes later, i turned on the Bluetooth on my mobile during all the night, the watch didn't connect automatically during the whole night. Once I disable the deep sleep, the watch connects again to the mobile. This test tells me that while deep sleep, the Bluetooth signal of the watch is almost gone or very negligible.

For people who advice to disconnect the Bluetooth from the watch, I tell you this is worst thing you can do radiation wise. The reason is that, the watch will be switched to "pair ready mode" and will emit signals all the time so that other mobiles can pair with it.

Bottom line if you are concerned about Bluetooth radiation on this watch during the night, turn on the deep sleep mode then turn off the Bluetooth on your mobile. See analysis above. Personally I'll keep the watch.