These processes, mainly cellular degeneration and organ failure, seem to be particular to most mammals in captivity. There are many kinds of senility, some due to over medication, some due to Alzheimer's disease and some to vascular disease . It is not only difficult to diagnose whether senility is part of an irreversible pathological process or a reversible one, but also which type it is. The Harvard brain atlas offers great insight and superb links about what happens to the brain with age, with or without pathology. There is a problem with diagnosis, as with any other patient it is imperative to know the patient.
Some people are very sensitive while others are stoic.
With age also the emotions flatten out somewhat, so that it can be difficult to diagnose depression rather than a recurrent upper respiratory infection. There is no question that mind and body very much influence each other. Psychoneuroimmunology is a relatively new science and studies precisely that. There are two other huge dangers associated with medicine and old age. Older people may have more than one physician and so multiple medications which may interact unfavorably and drugs are not routinely tested on the elderly.