A growing number of older Americans is falling into serious mortgage debt, with more than 3 million borrowers over the age of 50 at risk of losing their home to foreclosure.  That's according to a report from the AARP.

Since the housing crisis began, more than 1.5 million homeowners age 50 or older have already lost their homes to foreclosure.  That pushes the foreclosure rate among this group to 2.9 percent in 2011 from 0.3 percent in 2007, according to the AARP's Public Policy Institute. 

Another 3.5 million have found themselves underwater, owing more on their mortgage than their homes are worth.