There's no getting around it. No matter how well you take care of him, your dog will at some point begin to suffer the aches and pains and disorders of old age. In dogs, these can include arthritis, cancer, cognitive dysfunction syndrome (senility), congestive heart failure, dental disease, diabetes, hearing loss, hypothyroidism, kidney disease, and vision loss. While this litany of potential problems may sound depressing, the good news is that veterinarians now have more and better ways of treating them, especially when they're caught early. There's no reason why your dog can't have a long and comfortable old age.