I just find the cost of D&D to be a bit stultifying. And you can count on them dumping the system in 15 or so years to get everyone to repurchase it and shore up their profits. Yes, it's theoretically open source, and there's absolutely no reason you can't continue playing the older versions of the system. I've always had an aversion to any game, such as Deadlands, where each class needs its own rule book.
Regardless of whether or not this survey/study may be flawed, there's no doubt that long-term gaming helps with mental acuity and building community: it's a cooperative, creative endeavor that is very mentally stimulating. I'm not far from retirement, and while I don't expect we'll be moving to a retirement community or home, I definitely hope to engage in more gaming when that happens.
Of course, I do have the advantage of having worked in the industry at Flying Buffalo Games in the early '80s, they made Tunnels and Trolls and the Nuclear War card game, among many other goodies.