That's contradictory to leading sleep scientists like Matthew Walker, Peter Attia, etc. which is clear about need for chilly environment for sleep quality, eg < 21C. Granted, sleep science isn't oriented towards the genetics of the tropics yet, but there's plenty of evidence about temperature and sleep quality for more northern genetics anyway.
I agree with the parent. Killing the AC for weeks on end really helped me acclimate to the local temperature.
I'm not saying it resulted in quality sleep (as a Canadian - I set the thermostat to 13 degrees in the winter when sleeping, and my ideal temperature in the summer is about 18 degrees) - but you get used to the outdoor climate reasonably quickly (in my case, about 4-6 months).
Is 18 degrees assuming a fairly warm duvet covers / blankets? When I was staying hostels the dorms would sometimes be air conditioned and only a sheet would be provided for cover, and I struggled to sleep in anything colder than 21, and I'd have had it up to 22-24 if I could.
Sort of - now that I live in Michigan, and re-acclimated to a northern climate, at 21 I have to sleep on top of blankets or I overheat (though, I will find that after a few hours, my body cools down while sleeping and I may pull a blanket overtop me). 18 + a normal duvet is perfection. Cool enough for blankets, but not so cold that I feel uncomfortable.
This is mostly a meditation on the fact that I used to be able to sleep in temperatures of 26-27 in Singapore. The human body (at least this one) can definitely acclimate to local environments given some time and exposure.
Of course - no acclimating whatsoever will help you if the wetbulb temperature gets up to 35. You are just dead unless you can find some active cooling at that point fairly quickly.
I don't think it is contradictory - that is the point of adaptation that you expose yourself to something that is not optimal and your body learns to handle it. Think of it as artificially changing the range of conditions needed for good sleep quality by training.
