Of course, there are statistics on age, but based on the data I've seen, age is more an issue in terms of language training and when it's done. In other words, if someone has learned a language at 30 years of age and is evaluated at 60, they've probably maintained the language and won't necessarily have much trouble. On the other hand, someone who starts language training at age 60 is going to have more trouble.
On May 6th, 2008. See this statement in context.