That's an interesting idea, but there is no proof for this in the data, and in fact that's a common logical fallacy. Let's assume a population that lives on an

That's an interesting idea, but there is no proof for this in the data, and in fact that's a common logical fallacy. Let's assume a population that lives on an island that sits on the equator. One side of the island is polluted with radiation. It also features a kind of purple fruit that doesn't grow anywhere else and is not exported. Now let's assume that the fruit contains a cumulative toxin that causes people to die very young of brain cancer. A study without adequate controls might conclude: -- Living near the equator causes brain cancer -- living on this island causes brain cancer -- radiation causes brain cancer -- eating purple fruit causes brain cancer -- radiation causes people to eat more purple fruit Only one of these is true, but one could certainly invent reasons to explain nearly all of these correlations as causal. In the case of this study, an alternate explanation that makes sense is: -- diabetes causes dementia -- diabetics are strongly encouraged to drink sugar-free soda to avoid sugar intake -- therefore, diet soda intake and dementia are linked only through their common root cause, diabetes