There has been many posts about vitamin D levels being related to the onset of dementia. But, I am trying to find some studies that talk about the geographic distribution of dementia cases. My theory is that there would be less dementia in people living closer to the equator, but I haven't found a study that asks that question.

And I am also wondering if there is a time of year that dementia is more often diagnosed, because ones vitamin d levels might be lower.

Can anyone point me to some articles that talk about those those questions? My local alzheimer's society is interested in what I have mentioned about the relationship to vitamin d and dementia. (As if I am the one who thought of it!)