Steps vs. The Elderly

I am currently reading White Flight/Black Flight by Rachael Woldoff of West Virginia University.  The book discusses a neighborhood at the edge of a northern city (Philadelphia, I suspect) which was overwhelmingly Jewish as late as 1990, and became black in the 1990s.  One area of interest to new urbanists is its discussion of white "stayers" - elderly people who are not at all displeased with integration.  What drives them out is not crime or social disorder, but steps.  As they get older, they have more difficulty walking, and in particular using steps - which, as I have learned from watching my own parts, are much more treacherous for the elderly than level surfaces.  Because this is a neighborhood of rowhouses with lots of steps, a person who loses the ability to navigate steps usually has to leave the neighborhood and move to a retirement home.  

What does this have to do with urbanism?  I've seen some commentary (usually in the context of defending height limits) that treat walk-up apartments as the ideal urban form.  In an aging society, this ideal is simply not realistic.  Walk-ups are certainly fine for young people on the way up (pun intended) but they simply cannot be the dominant urban form unless we are prepared to have communities denuded of seniors.