Geographic variation in T1 incidence: why?



Welcome, @kalle. I didn’t know that statistic! I have had diabetes for nearly 50 years and have lived in England, Canada, and a year in Italy, and except for going to diabetic summer camp as a kid a few times, I have never met or worked with another T1 diabetic (not that I knew of, anyway). Then I visited Sweden recently and met three of them in a week! One even told me about Canadian research into diabetes and genes that I had never come across.

Welcome, introduce yourself here!

Fascinating, do the incidence rates between countries differ that much?


@Boerenkool,the variation is apparently very significant. I found a list with a number of countries here: https://www.diabetes.org.uk/about_us/news_landing_page/uk-has-worlds-5th-highest-rate-of-type-1-diabetes-in-children/list-of-countries-by-incidence-of-type-1-diabetes-ages-0-to-14
Looking it up wouldn’t have occurred to me out of the blue, but I guess we talk about this statistic in Sweden since we’re close to the top. It seems to be common knowledge among diabetics around here.

@Beacher, I like to think that we are pretty open about it here, though I don’t know what it’s like in other countries. Could that make it more likely to notice? I will just casually inject at the table when having lunch with my colleagues at work, and no one raises an eyebrow.


It’s hard to get really robust statistics for some countries (where I imagine those with Type 1 simply die of “unknown causes” and health information isn’t gathered as systematically) but from what I understand there’s a 500-fold or more difference between the countries with the highest incidence (like Finland) and the ones with the lowest, like Venezuela.


This may also be partly generational? My 14-year-old son has done it all over the world and does not care. But we have not met older people who are as overtly diabetic. Admittedly we have lived in conservative areas.

In any school he was a part of, kids didn’t care btw.


Wow, the incidence in Finland is remarkably high! Is there a known cause of the high incidence rates in Finland, Sweden and Norway?


I am curious if there is any understanding that the founding gene pool was small for Scandinavian populations? If so it could be generic drift.


I’ve read that something like 75 percent of the odds of T1 can be ascribed to genes…but I’m not sure if there’s a 500-fold difference in the incidence of those incredibly common genes in the Scandinavian populations versus those in other countries.

However, I’ve also read that the incidence of T1D in Finland has, in recent decades, been much higher than just across the border in Russian Karelia (which is much less developed.) Genetically these populations are quite similar so it’s a bit of a mystery.



I think there must be a lot of factors at play in the higher incidences: genes (HLA complex prevalence), ethnicity makeup of the countries (Caucasians are more at risk for developing T1D), their national healthcare system (we know infections may be that 2nd hit necessary, so country’s initiatives for vaccines or infection prevention measures may play a role), probably something to do with geography or climate or diet could be playing a role???


Additionally, there are at least ancedotal reports of spikes such as this one:


Which lends some credence to the genetic predisposition, followed by a viral or other environmental trigger.


yep! I know anecdata is just anecdata and we can never really figure out for sure. But I can’t help noticing that the same year that Samson was diagnosed, there were a ton of “welcome new family” messages in our local diabetes support group where the kids were roughly the same age as Samson. As if a particular bug was going around that tended to hit kids of the same age, and some of them wound up getting T1D


My guess is that there are definitely common gene factors that put one at risk for these things, but then also probably many different factors that can trigger them, which is why they are probably so hard to pin down. Especially when you add to it the fact that it may also be a roll of the dice as to whether the person exposed to that trigger goes on to develop Type 1, celiac, or any other autoimmune condition. Also, I’ve read in books that whether the immune system generates antibodies or not may depend on the state of the rest of the body at the time of exposure to something else…so that may be yet another factor that compounds things.

Different condition (though also autoimmune), but when I developed Graves’ disease, there was a lady working in my office who also had long-term Type 1. She was diagnosed with Graves’ disease literally within about a month of me. So we joked that it was something in the water at the office that triggered it. And who the heck knows, maybe it was!


I thought that was thought to be related to less sunshine, and lower vitamin D levels.


Welcome to the forum Kalle. Your comment about Sweden having the second highest rate of T1D in the world interested me. Do you have more information on which other countries have high rates of T1D?

Welcome, introduce yourself here!

I found this ytube very interesting and have posted about it before (not exactly sure when/where though).

At the 38:11 mark it shows a graphic of how, in Finland, the recommended dose of vitamin d dropped and the increase of type 1 diabetes increased.


I notice he says Rochester NY, instead of Rochester MN (on chart).
Rochester NY is very cloudy, not sure about MN.


My clinic is participating in a long-term study called TEDDY which is trying to identify the causes of T1D by following a large number of participating children over many years. My university has a page where they publish results, but it’s in Swedish. Some of the participating universities are in the US though, so I would think that there’s information available in English somewhere.

They have confirmed a correlation between low levels of vitamin D and autoantibodies, and have also found a number of connections to various genes, in addition to the ones previously known. Still, it seems difficult to draw firm conclusions because the incidence, in absolute numbers, is still small. Even with thousands of participants in 4 countries, only a little more than 300 have actually developed Diabetes. One of the upsides is that it can be detected long before it causes any symptoms at all. This means no DKA, and a slower destruction of Beta-cells with early administration of insulin. There has been some discussion about general screening of all newborn children for this reason.


When Liam got diabetes, he was still breast feeding.


I’m sad to hear that he got it so early. That makes it seem very random and unfair, which I suppose isn’t far from the truth. Even though some genetic markers increase the risk significantly, in most cases there is no observable heredity at all. I guess all that randomness can obscure the patterns.


Forgot to add that no one on either my wife’s or my side had ever had T1D before either.