According to demographic info about print and digital comic fans gathered from Facebook, digital comic fans are older and skew much more male than print fans, according to GraphicPolicy.  The difference in age was over a decade (30s for digital vs. 20s for print), according to the report.  Men were over 81% of digital fans and only around 63% of print comic fans.
The info on digital comics consumers’ age would seem to support what we’ve been hearing anecdotally, that there are many returning lapsed comics fans among digital consumers.  It also makes sense that if the digital consumers are indeed returning fans that weren’t buying comics recently, that digital sales are not cannibalizing print to any great degree, another observation we’ve been hearing anecdotally (and which the robust sales of DC’s New 52 would also seem to support). 
The gender difference may be due to the types of comics that have moved to digital first; with fewer independent and manga titles, there may be less to attract female consumers in digital than there is in print.