I grew up in Norway. The coldest winter I experienced saw 3 weeks of -30 celsius. I've lived in London the last 22 years. I didn't freeze more in Norway. We had better insulated houses, and far better winter clothes, because we needed to. And so if anything I more frequently get "caught out" and have to add extra layers of clothing etc. in the UK because you can get away with not being prepared for a cold winter here, while in Norway you will have a proper winter coat etc.
My own apartment is so heavily insulated that even in the winter, it’s almost to make the indoor temperature drop below 20!
There are obviously places in the US with far more extreme temperature fluctuations, but most of them are fully car dependent and many people living there can wind up experiencing the weather firsthand for seconds at a time (in parking lots), unless they deliberately choose to do otherwise.
I understand the sentiment. While we have done climate control to our comforts, I am talking of environmental factors at large. Just because Norway has great heating & insulation doesn't imply Scandinavian climates are as good as Spanish ones. We get exposed to lower temperature climates in higher latitudes, and that thermal effect if any should add up over the few decades of human lifespan or even in the genetic assessment in terms of prevalence (in my OP). We are talking in statistical sense - not an individual trial.
Proper & consistent indoor thermal regulation have been around in past few decades, whereas useful medical record keeping has been around for a good two centuries in most of Europe & America (maybe slightly longer). So, my inquisitiveness is to check if this hypothesis matches with statistical observations in the northern population. And several medical studies do factor in environmental temperature (going by my brief exposure during grad school). These factors are not disregarded because we have great ACs for temperature management or sunscreens to block the UV. If human interventions could so effectively mitigate, skin cancer prevalence would be uniform around the globe (which absolutely isn't) due to effective sunscreens sold nowadays.
Human bodies lose heat very quickly. We evolved from a primate line which lived in South Central African plains. Our hand/feet digits are great radiators. Although still debated, our skin tone originally could have been light, much like the skin under the primate coats (with brown and African skin tones being later developments in evolution, when we started to get less furry & produced higher melatonin). So the evidence generally points in the direction that we are just another warm-blooded species without much thermal attributes. Given that, environment should show some kind of statistical difference if this cancer pathway's reliance on temperature is so pronounced. Its hard to measure, because there are several confounders in the biochemistry. It is also hard to find a body of people who have lived in both cold & hotter climates simultaneously to make direct comparisons
Edit: some more details.
I would argue based on experience that I would expect people in London to have been exposed to more cold than the average Norwegian.
By all means, it's worth checking, but my point is that if you don't find a difference, the logical conclusion is not that cold does not work, but that people in colder places don't get that cold.
EDIT: I would also argue that proper heating has been around for centuries, not decades. Regulating temperature down is a lot harder than regulating it up. In fact, the house I grew up on was a log house heated in part by a wood fire during winters - we used electrical ovens during fall or spring, but the wood oven could easily dump far more heat into the house in a very short amount of time, because it heated up a large stone chimney that was exposed in all the main rooms. But even a tiny cast iron oven can heat up a small house in no time if it's decently insulated - Norway's best established current cast iron oven manufacturer is over 160 years old. My grandparents cabin is heated that way, and you'd get it from freezing to room temperature in less than half an hour.
Life in the midwest is organized around staying warm and it works very well.
We do appreciate the blue skies and the sun of California, however. In the midwest in the winter, you can often go weeks without seeing the sun.
We also like the houses in California. They're historic and beautiful and in many cases greatly elegant. Also, easy (arguably continuous) outdoor access is a beautiful thing. But there is great irony in paper maché houses being, relatively, so much more expensive.
https://www.thrillist.com/travel/nation/us-states-with-the-w...
[1]: https://www.columbia.com/p/mens-centerport-ii-jacket---tall-...
I have a jacket similar to this one [1], and I find it to be a nice medium. However, if I had to do any work outside, I would get an actual parka.
Though I don't doubt that I'd need a heavier/longer jacket if I were further north, but here in southern Ontario it's more than good enough.
*Not an ad, just sharing what keeps me warm
One needs something that reaches knees to stay warm in lighter trousers.
Early 1987, perchance?
I think it's reasonable to go look for existing evidence, but it'd also be difficult to extrapolate.
Plus the persistent cold exposure may not be there due to warm clothes.
For me more interesting is the story of cancer among aboriginal population of Australia. They do not use much clothes and at night there it can be rather cold.
Brown fat activation is not efficient from an energy perspective. If you live somewhere cold, with generally sparse food supply, burning precious calories to warm yourself up isn’t a winning strategy. I highly doubt brown fat activation is more prevalent in the colder climate populations.
If one does not do a physical activity and does not spent energy to warm the body, the body instead spends that energy budget on various expensive activities like synthesis of hormones (like testosterone for males) or to activate immune system more than necessary leading to asthma. But immune system for normal function does not require much energy and as long as one eats enough, the persistent cold exposure should not affect it.