Does age in grappling matter?
One of the great things about BJJ is that it isn't anywhere near as hard on the body as something like judo or boxing. If you train sensibly, you can keep rolling long into old age: if you're really careful, then you might be able to emulate Helio and keep going right up until your death (he was still on the mats at 95).
As per
FAQ, that also goes for starting BJJ later in life. My favourite example when it comes to the "am I too old" question is
this guy. He started training at RGA when in his eighties, earning his blue belt in 2007. So while it's a cliche, it really is never too late to start.
There's also a good thread with discussion of training a bit later in life (especially how to cope with injury, arthritis etc)
here.
You could also check out the Roy Harris instructional
BJJ Over 40.
A 16 year old vs a 25 year old. Both the same weight just different ages. [...]
And the other way.
25 year old vs a 45 year old.
As mentioned, generally age is accompanied by certain attributes. At 16, you're unlikely to be as strong as somebody at 25 (though there are exceptions: plenty of very powerful 16 year olds). Similarly, at 45 you aren't normally going to have the same level of fitness as somebody who is 25.
However, that only matters if both grapplers in your example are of the same skill level. In that case, strength, stamina, speed etc definitely matters, so the person in better shape is likely to come out on top. All else being equal, athletic aptitude makes a huge difference.
If the older or younger person is more skilled, then that changes things. For a start, strength and endurance immediately become less important, because one of the main things you learn as you develop your grappling is how to relax and use timing to your advantage.
The aforementioned Roy Harris is a good example: he uses a slow, pressure game that works just as well when you're older, because it doesn't rely on strength and endurance. Instead, its about good timing, leverage and how to use your weight.
Therefore a forty-five year old who has been training for a number of years is probably going to be able to use their technical ability and understanding of timing to overcome a stronger, more athletic twenty-five year old who has only been training a few months.
To make a sort of Top Trumps reference, if you think of it as a scale of 1 to 10 for both strength and skill, then somebody with 10 strength but 1 skill is going to find it tough against somebody with, say, 6 strength but 10 skill. By the same token, that same very strong, unskilled person may be able to overcome somebody with a small amount of skill but not much strength.
Wearing a gi also helps, as with a gi, much easier to slow things down due to grips. Without the gi, physical attributes come into it more.