What are the signs of a cat ageing. My cat was and is a short haired domestic, but he has got more fluffy.?

I only ask because a friend who had,nt seen him in a couple of years said he was looking old. I guess I have noticed he is not as sleek furred as he used to be when he was young. He is very healthy for his age but he does look a bit degraggled, I still groom him, So is fluffy fur a sign of old age.