Most of the signs of senile dementia that we might have, pets have too. A typical age-related change in pets is standing at the wrong place by the door when wanting to go in or out. Some pets bark or meow absently. Others seemingly forget why they are where they are. This can be associated with loss of house training. The term 'canine cognitive dysfunction' or CCD has been coined to describe the deteriorating behaviour changes of old age in dogs. The term itself is a mouthful but it is useful because its use recognises that this is a medical disorder. We usually use the term senile dementia.
Routine, daily mental stimulation is beneficial. The drug selegeline, developed for use in us and used for delaying the development of advanced signs and symptoms of Alzheimer's Disease, is licensed for use in pets with senile demetia. If your pet is having "senior moments", check its behaviour. Some aspects of aging are irreversible but others can be delayed, even reversed with effective use of licensed medication.