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Comment by rm999 | Hacker News Reader

That's almost exactly how they found the connection, from the article:

> Early epidemiologic research showed that incidence and death rates for certain cancers were lower among individuals living in southern latitudes, where levels of sunlight exposure are relatively high, than among those living at northern latitudes

An obvious problem is confounding variables, this isn't a controlled correlation in any way. The article goes on to say:

> However, additional research based on stronger study designs is required to determine whether higher vitamin D levels are related to lower cancer incidence or death rates.

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This reminds me of autoimmune disease like MS. They are more common in higher latitudes (where there happens to be less sunlight), and there is a connection to low Vitamin D that isn't understood.

While attempting to understand the link better, UW-Madison researchers recently produced data implying that the ingredients of some sunscreen products may provide benefit in preventing MS. https://www.acsh.org/news/2017/07/28/sunscreen-ms-and-hard-b...

There was a piece in the New Scientist a couple of years ago that said type 1 diabetes seems to be correlated with higher latitudes. They suggested it was related to Vitamin D.

Yes, like MS, type 1 diabetes is considered to be an autoimmune disease. It's surprising to me as someone who hasn't studied medicine how related to each other autoimmune issues seem to be. Rheumatoid arthritis and latitude is another one that follows this same pattern. This article from 2010 about rheumatoid arthritis also mentions the link to low vitamin D levels, and that the link isn't understood.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920915/

Are there any statistics that low levels of D at northern latitudes decreases life span? Without such decrease even if it will be confirmed that low D causes cancer, it will also imply that higher levels of D causes other problems that just as deadly as cancer.

One example (mentioned elsewhere in this thread) is that incidence of autoimmune disorders goes up as you get farther away from the equator

Edit: I suppose that’s decreased health span more than decreased life span

As D suppresses immune system among many other things one should not be surprised to have such correlation with incidents of autoimmune disorders. On the other hand life span in Canada is few years longer than in US while I got impression that levels of D deficiency is comparable in US and Canada. So I guess it is very open question if low D is really bad.

Additional research such as EPIC series of research? One of which studied the impact of vit. D levels in blood on all cause mortality corrected for many factors?

(Note: EPIC studies Europeans.)

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