She said she was an undergrad while he was in medical school. Meaning they have to be at least 5 years apart. In season 3, House refers to her as "nearing" 40, meaning she's at the very least 37.

Also, he went to Hopkins before that, thought they don't say for how long, so that adds to his age as well.

I 'm going to do a timeline and post it on my LJ. Just for kicks and giggles.