Yes, Alzheimer's rates are declining significantly in the US.   They have declined about 25% over the past 15 years in the US according to a recent NYT article.

Stats in the US don't hold true for Canada.  The link below provides stats showing alarming growth.
http://www.alzheimer.ca/en/Get-involved/Raise-your-voice/Latest-info-stats

It's also interesting that the US, about 15 years ago, decided the threshold for B12 deficiency in serum B12 tests would be raised to 350 pg/mL from 200 pg/mL for people over the age of 60.   Guess what?  The instance of "B-12-deficiency-masquerading-as-dementia" started to drop.   This seems to be what is driving the decrease in Alzheimer and dementia in the US.

In Canada, the lab tests conducted at one major diagnostic lab don't flag B12 deficiency until below 138 pg/mL!!!   Also, in Canada, you have to PAY for your own methylmalonic acid test, which is key to determining deficiency in adenosylcobalamin, one of the two key active forms of B12.

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