While looking up the various senses of "while" in the Oxford English Dictionary, I came across the following:
[B 2 c.] In modern colourless use: At the same time that, besides that, in addition to the fact that; often = and at the same time, and besides.
http://www.oed.com/view/Entry/228336
I'm not sure what is implied by "colourless use" here.