How old is old? According to a study by Michelle Barnhart of Oregon State University, whether someone is "old" depends not on age, but on ability to do things, like shopping, for example:
New research finds that for most Americans, old age is not heralded in by a particular birthday, but rather by how a person acts.
In particular, people who still shop for themselves or take care of their own household chores are less likely to be perceived as old, new research shows. [...]
"When people in their 80s or 90s exhibited characteristics that society tends to associate with people who are not old, such as being aware, active, safe or independent, they were viewed and treated as not old," Barnhart said. "In this way, they were able to age without getting old."
LiveScience has the article: Link