Nitrates in meat have long been known as a problem for other reasons too, haven't they? Particularly with regards to various digestion related cancers - this gives another reason to cut back.

The linked artical is a bit ambiguous though; initially it says:

diet with lots of meat and processed foods

and then later

patients with Alzheimer's tended to eat a diet rich in "processed food and meat items"

is "processed" in the second one referring to just "food" or both food and meat?