Yours is a tough call.

Perhaps, ethically, your father is entitled to know. Current medical ethics speaks profoundly to the innate right of an individual to know, precisely, what is the charted diagnosis and is also entitled to a full explanation of the diagnosis, its potential implications and the potential courses of action, whether remediative, curative or simply palliative.

However, it is questonable as to whether, at this stage, the diagnosis will be of significant intellectual content to your father. It may be a bit of data that will drift into his brain, then drift out. The time for cognative awareness may well be behind him, by now. This disease is a quirky viral circumstance, one that has a challenging set of behaviors to it.

Like so many others posting, I have my own story.... some 35 years ago, my brilliant mother, who graduated from medical school at the age of 23 and did cutting-edge research for her master's in public health, began to decompensate radically after the death of my father. Given her alchoholism, my brother and I assumed that her declinication of behavior was probably linked to that, but her behavior became rampantly unsafe - driving her car backwards on high mountain roads, triple-loading a shotgun and - firing it (Thus blowing up the barrel, rather efficiently)..... and so on. My brother and I had her committed against her will to a mental institution. Following her detoxification, they began to tease apart her bizarre behavior patterns, at one moment cogent and articulate, then at the next, quite, quite mad. They diagnosed it, conservatively, as a viral degenerative brain disease of unknown etiology (Alzheimer;s was just coming into public understanding). We had it confirmed by a prominent private health clinic in the midwest.

We went forward with establishing guardianship for her, which required that she be told, precisely, what the circumstances were. With the flash of brilliance that was typical of her in her "good state", she identified the diagnosis immediately. By the end of the hearing, that information had slipped from its intellectual moorings...........

My mother's resources, financially, were substantive, and I arranged for her care in increasingly controlled medical enviorments of great quality.. there was no question of home care. She lived for 19 years in a declining state, not remembering names after the first five or six. I obtained, thorugh the court, an advanced directive that limited extraordinary measures in the face of health failure. When the nursing home revived her after her first respiratory failure, I threatened a lawsuit, forcing the instituiton to grapple with the advanced directive. Two weeks later, my mother died, quietly, no longer remembering how to breathe. She was not in either functional or cognative pain.

So, to some extent, I think the question is moot. What you, Soldier John, can do, however, with that military mind, a can-do focus and a capacity for pragmatic action is substantive, and that includes:

making sure that your mother, or you, have an advanced directive. By now, your father cannot participate in this, and you may well have to petition the courts for an objective expression of an advanced directive. Your father's interests will be addressed by an attourney ad ligtum (sp?) appointed by the courts..... and these folks will take their job seriously.

Making sure that the advanced directive is coupled with a durable power of attorney that provides either your mother or you with sweeping and comprehensive control of your father's finances. period. Absolutely and without question. This man may need pocket change for chewing gum, but he should not be writing checks or handling a credit card.

Both the advanced directive and the power of attorney can be devloped in consultation with an attorney versed in geriatric law, a burgeoning subspecialty.

make sure that you and your mother have an action plan in place when,(not if, but when) your father's health deteriorates further. There may be a time (relatively shortly) where your father's lack of impulse monotiroing makes him hazardous to your mother and to himself, and he will need to be institutionalized. There are now nursing homes with specialized Alzheimer's units. Do the research NOW, not in crisis mode after your father wields a knive, gun, car keys, or some other lethal object.

Make sure that your mother obtains respite care. Her role is almost impossible and will grow more and more wearisome over time.

Be aware that when your father dies, your mother may well engage in her own extreme emotional decompensation for a period of time. When she no longer needs to hold it together, she may well not choose to. respect that, and create, if you can, a safe manner for her to heal from the ravages of dealing with the death of her husband by baffling inches.

And,emotionally - be aware that you may wish to acknowledge your grief over the loss of your father incrementally. the Father that you knew has already, in part, died. Tough recognition, but a reality of this horrific disease.