Articulate nuns, dementia and belief

Here's a brief follow-up on our post the other day about Alzheimer's disease. It's a story that's been dribbling out for the past few years about a study of nuns and dementia. The first results from this study suggested that nuns who wrote the most articulate application letters when they were 20 were the least likely to have dementia as they aged. So, the association of early language ability with risk of dementia reported in this story from the BBC is not new--whether or not it's 'real' or actually predictive, given that we can surely all think of very articulate people who went on to develop dementia (the story itself mentions the British novelist, Iris Murdoch, perhaps the most famous example).

So, although this possible association raises many questions (is senile dementia the quantitative end-point a life-long trait that begins at birth? Can articulateness be learned, or is inarticulateness a characteristic of a person that is also a predetermined product of a doomed brain? is this association meaningful?), that's not what caught our attention about this story.

What interests us is the assumed association of plaques with dementia. As the story says,

Dementia is linked to the formation of protein plaques and nerve cell tangles in the brain.

But scientists remain puzzled about why these signs of damage produce dementia symptoms in some people, but not others.

Why are scientists convinced that these signs of damage are what is producing dementia? This assumption is being questioned by some (e.g., The Myth of Alzheimer's: What You Aren't Being Told About Today's Most Dreaded Disease, by Peter J Whitehouse and Daniel George), but not by many. Indeed, a quick search of the literature suggests that this 'puzzling' finding is frequently reported, but it is assumed to represent 'pre-dementia' in those with plaques but without confusion. And, it's impossible to refute, as it can always be said about a clear-thinking person with plaques that they died before the disease became manifest. A few early observations led to an equation in peoples' minds of plaque and disease, and became entrenched.

But it's an assumption, a belief. It may fall out of favor, but that will take time as beliefs can fall hard. In fact, one prominent Alzheimer's researcher we've spoken with, a non-believer in plaques as causal, or even in the idea that a single disease called Alzheimer's exists, says that she thinks the field of dementia research is due for a real shaking up. It's time for a new model of dementia, and it will have to allow for complexity.

Although we all like to think that science is based squarely on fact, not belief, this is another example of how that's not as completely so as we'd like to think.