Frankly, having taught some basic computer classes, while not absolute, I would suggest that in general, that some of the things that come with being elderly, and young, do play HIGHLY into the general computer competency.
When I taught classes with both old and young people, anyone under about 25, even if they claimed ignorance, had been exposed and generally only required a very small push to direct them to what they wanted to do. They understood the basics of operating especially a GUI. They've grown up with it in our culture. They have been exposed to concepts.
Contrast this with people who while smart, were older, especially if over 40. They simply often times lacked the familiarity, so something as basic as say, selecting a particular object on a menu took a lot of work to figure out what was going on. Repeat this for the many common GUI interfaces... and that familiarity meant that in general, being elderly does have a strong correlation with what's perceived as illiteracy.
I've also been the one doing tech support for PhDs. Really smart people... who haven't been exposed to things. One of the people I helped with things did projects on Quantum computing. One of the few people I know who impresses me with raw intelligence. Generally, though the experience was with things like Fortran (which works much faster than people think).
So it's nothing inherent about being elderly/young, except for the times they were exposed to, which clearly does have an effect on computer literacy. There are of course exceptions.
There are also things like my opinion, that in general, a younger person generally doesn't understand the way computers work as well as an older person with equivalent education for their time. This is due to the rise of things like Object Oriented Programming, Java, etc. Consequence of the times they are in.