I'm 99% sure that it does not.
First, the power levels are generally low, and it's spread spectrum / freq hopping, so the behaivior would be similar to Bluetooth.
If your Bluetooth and WiFi get along, then 802.15.4 should be fine.
I have some 802.15.4 demo kits running at home (next to my Cisco APs) and I'm not seeing any significant interference (of coursr, my wireless density is pretty low as well ... not a real test).
Good Luck
Scott