The older cats will start urinating and defecating out side the litter box even if it is well trained. The younger cats will respond faster to the challenging tasks or situation where as the older cats will struggle to respond to these situations. By this way, you can easily find out the ageing in cats.
The older cats will not get up in time as it used to be earlier. At times the cat will be sleeping all through the day. The older cat may be awake in night and will be seen sleeping at day. These are few signs of ageing in cats and require special attention.