Alzheimer's life expectancy is not the same for everyone. Some people die within five years, others live for twenty. Also confusing the issue is that there's really no way to know when the disease began, as for many people symptoms take quite awhile to show. Much also depends on other health issues, such as risk of heart disease.
This question really needs to be answered by the physician attending the person with the disease, and even then, it will be a guess. There will likely be a number of years left for this person, barring other ailments.
My father-in-law also has moderate Alzheimer's which is in stage 6. Pretty much early or mid-stage 6. He can eat and walk with a cane, but most of his intelligent knowledge as MD PhD. before 2004 is gone. the thing is when he was diagnosed in Nov 2006, he was like in mid-AD stage. After Nov. 2007, he has entered into stage 6. It is very slow for him. The nurse said maybe he is too intelligent before so it declines slowly and it is out of box situation. However, this is not going to last forever. I would say in 1 or 2 years, he will be in stage 7, the end stage. But it makes it hard to plan for his future such as nursing home or staying at home as it is expensive to have home care. On the other hand, he has had congestive heart failure twice since Nov, 2008, so this means his heart got mostly 4 more years. He would die of heart failure instead of AD in 5 years unless something unusal happens. So it is different with everyone. He is 88. In his case, I think it takes like more than 10 years for AD (I suspect he got it in 2002/2003).
Normally the doctor does not tell you how long the person has left for AD. I think one reason is that the doc. does not live with the patient and it is hard to say so. Normally for end-stage, it is 2 to 3 years. For moderate stage, in my experience, it takes forever like 5 years at least. I got some info. about the years somewhere in the web but I don't have it handy.
Here is the website that I was talking about:
Hope this helps.
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