Why does turning on bluetooth add a delay to my USB audio device?

I am currently running a 2012 MacBook Pro 2.6Ghz Quad core with 16GB RAM and Mountain Lion.

I have a 27" Samsung monitor running at 1080p on my display port out and a USB mixing desk feeding monitors on one of the USB Ports.

When I turn on bluetooth to use an external mouse and keyboard, this adds a delay of about a second to the output to the USB audio device, this means that in Logic the timeline goes out of sync with the audio. Turning off bluetooth and rebooting the computer gets rid of the delay.

Can anyone suggest why this should happen? Is there a way of solving this issue without using a wired mouse and keyboard (which would also require me to use a usb hub because there is only one spare USB port.)

Its very annoying, as I have bought the bluetooth mouse and keyboard especially for the purpose of using the big screen for music production.

Thanks for any help you can provide.