There's no trend (and if there was it's too small a sample to be meaningful !). But FYI we have 18 team members from Levels 27 to 56. In our current war we have 11 active players, but I know a few, like myself, are contributing to support the team even though we don't like the concept.
We stay private as a team, (it's a kind of rule), but we once shared our ages, and they range from early 20's right through to 60+. Again it's a mix of ages that are participating in the war.
For what its worth my theory is that everyone who chose to play SimCity to any reasonable level, has already pretty much rejected the war games. People are playing Club Wars at the moment because it's a new element, but I think interest will drop off.