Loss of teeth. Gum and tooth infections. Cancerous and inflammatory lesions in the mouth. Other symptoms are more frequent regurgitation and progressive emaciation. Constipation caused by less interest in food, lower intake of fluids, hairballs.
Grooming is essential.
Anemia is often secondary to a larger problem. See the vet. Feline leukemia which requires immediate veterinary attention. Most cats are jealous, but aging cats are especially jealous of other animals and even human members of the family. It is important with an aging cat to remember all the good years you shared and make the cat feel comfortable, loved, and wanted.