Sleep and cognitive functions are affected by too low or too hot temperatures

[zbigi]

This is contrary to the notion that "humans adapt to temperatures, we don't need to live in 23 C". Perhaps we do adapt, but at some loss of quality of life?

[AxelHeyst]

Are these numbers based on heat-adapted populations? Or did they just expose people accustomed to 23C to higher/lower temps for a few days or few weeks and go "yep, performance declined"? (in which case, duh).

Heat acclimatization takes months and years. All these graphs seem to be saying is "people who are accustomed to a certain temperature range experience decreased performance when they are exposed to conditions outside of their comfort zone".

Let's see the methodology and see if these numbers have anything to do with actual adaptation.

[chenda]

We are on our third heatwave of the year so far and I am considering buying some air conditioning. My flat has a lot of thermal massing which is good (unlike a lot of modern construction) but a portable unit might be a good idea. But part of me thinks I should just gradually adapt as the summers get hotter. Any opinions or recommendations are welcomed.

[Jean]

Jump in the river every time you feel too hot, and when you take something out of the freezer for consumption, let it unfreeze in your cloth.

[AxelHeyst]

The trick with adapting to higher temperatures is you've got to avoid air conditioned spaces as much as possible. Not a big deal if you go into an AC'd grocery store every once in a while, but if you have to spend hours/day in an office or other environments that you don't control, your adaptation potential is limited.

[theanimal]

Heat is known to decrease cognitive capability. From my understanding, that is a well researched backed statement. Upon entering office, Lee Kuan Yew famously mandated A/C in all government buildings to maximize cognitive performance of all government employees. He cited air conditioning as the single greatest factor in making development possible in the tropics, enabling workers to be more efficient and work longer.

There is also the controversial (?) idea that warmer countries have lower IQ and work ethic due to the heat. There are of course many other factors within these countries that could cause the same result, which makes it more difficult to narrow down whether heat is THE cause or just one of many causes.

[jacob]

Another variable that increases with temperature is violent behavior. This is maybe not so surprising, but the correlation shows up in crime stats.

[theanimal]

Here are a couple studies that examine the bulk of the research and come to similar conclusions. There are ocassionally some studies that suggest heat can improve cognitive function, but that is on a limited time scale. Prolonged heat exposure decreases attention, recall and reaction time among other factors.

https://journals.physiology.org/doi/pdf ... 00070.2023
https://www.sciencedirect.com/science/a ... 2318304104

And for fun here's one on cardiac impact
https://www.nature.com/articles/s41467-025-57868-6

[AxelHeyst]

Chenda, advice is to move to alaska. It hits 78F/26C here and they issue a heat advisory.

[chenda]

@theanimal - interesting. It has been noted that colder countries and regions tend to be wealthier than hotter countries, in the industrial age anyway.

Chenda, advice is to move to alaska. It hits 78F/26C here and they issue a heat advisory.

ha, I wouldn't rule out moving further north at some point, or upwards to higher terrain.

[zbigi]

Are these numbers based on heat-adapted populations? Or did they just expose people accustomed to 23C to higher/lower temps for a few days or few weeks and go "yep, performance declined"? (in which case, duh).

They studied the general population across countries. Here's a quote from one of the metastudies:

The largest investigation of the effect of ambient temperature on sleep thus far – a study based on billions of repeated sleep measurements from sleep-tracking wristbands collected in 68 countries over two years – found that increased nighttime ambient temperature shortens sleep duration, primarily through delayed sleep onset, with stronger negative effects during summer months, in lower-income countries, in warmer climate regions, among older adults, females and after controlling for individual and spatiotemporal confounders.

[Jean]

That makes for an interesting global warming feedback loop.

[chenda]

I recall an observation somewhere that cold countries would traditionally have to stockpile food for the winter months, which gave rise to a culture of planning ahead, saving and deferred gratification. Whereas tropical regions have abundant food all year round and didn't need to plan ahead so much.