How to Sleep When It's Really Hot

[GordMay]

A 2018 study [1] found that, a one-degree-Celsius increase in room temperature, translated to about three fewer minutes of sleep, potentially contributing to reduced cognitive performance among college students, living in un-air-conditioned buildings.

Another paper, from 2012 [2], found that heat impairs the kind of sleep, your body needs, to wake up feeling rested and refreshed. People are also less likely to sleep through the night, in a hot environment, even if they’re tired enough to drift off initially.

The most obvious solution is to use air conditioning, to keep your berth cool, but that’s not always an option, for most cruisers.

A scientific review, co-authored by Shahab Haghayegh [3], found that:
taking a hot shower [or bath], an hour or two before bed, can improve sleep.
That warm environment can trigger physiologic changes, that lower your core temperature, and help you conk out. (The average bedroom isn’t hot enough to cause this shift on its own, even if it feels uncomfortably warm.)

Fans do ‘double duty’. They keep you cooler, and they provide white noise, which masks environmental noise. Circulating air, even if it’s warm, does seem to help people sleep better.

Use sheets and pajamas in breathable fabrics, like cotton and linen.

If you share your bed with someone else, consider using separate covers, especially if one of you sleeps hotter than the other. At the very least, it may offer some physical separation, on warm nights.

[1] “Reduced cognitive function during a heat wave among residents of non-air-conditioned buildings: An observational study of young adults in the summer of 2016" ~ by Jose Guillermo Cedeño Laurent et al
➥ https://journals.plos.org/plosmedici...l.pmed.1002605

[2] “Effects of thermal environment on sleep and circadian rhythm” ~ by Kazue Okamoto-Mizunocorresponding, and Koh Mizuno
➥ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427038/

[3] “Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis” ~ by Shahab Haghayegh et al
➥ https://www.sciencedirect.com/scienc...552?via%3Dihub

[GordMay]

See also:

“The Effects of High-Temperature Weather on Human Sleep Quality and Appetite” ~ by Guozhong Zheng et al

...
Conclusions:

Sleep quality at 32 °C was the best, followed by that at 28 °C, while sleep quality at 36 °C and 38 °C was the worst. The significant effects of high temperatures on sleep quality were mainly reflected in sleep duration and shallow sleep.

Temperature had significant effects on sleep calmness, difficulty in falling asleep, sleep satisfaction, and sleep adequateness. The effects of temperature on these four indicators were significant.

High temperatures led to a decrease in body temperature and an increase of the average heart rate and respiratory rate. Thus, wakefulness increased and SWS decreased.

For subjective appetite, effects were mainly reflected in appetite at lunch, and there was no significant effect on breakfast and supper. Subjective appetite for lunch at 32 °C was the best. Hunger and the desire to eat before lunch at 36 °C were significantly lower than those at 32 °C, and food greasiness before lunch at 38 °C and 36 °C was lower than that at 32 °C.

For objective appetite, the meal weights of lunch were larger than those of supper, except for 28 °C, and the meal time of lunch and supper was longer than that of breakfast. The meal time of lunch was longer than that of supper except for 36 °C.
...

Study ➥ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6351950/

[dlj]

Very surprised 32 C was considered the best sleeping temperature. That's pretty hot by my standards.

dj

[CaptTom]

I was thinking the same thing dj.

Could it be they mean body temperature?

I admit I didn't read the whole thing. I've been doing nightly sleep tests for over 60 years. My results indicate that ideal ambient temperature for sleep is around 65-68F (18-20C). Just enough to feel uncomfortably cool without a blanket. I do concur with the finding that a fan makes much higher temperatures tolerable.

[Chotu]

also surprised about the ideal sleeping temperature. I have carefully studied my own sleeping and found that my data agrees with Tom. 65-70F (18-21C)

One of the most difficult parts about sleeping in boats and RVs however is the thermal loading from the day that sits in the material you’re surrounded by.

I have often noticed that going to bed is around the worst time of day for heat problems. The wind seems to die down because there are no more thermals rising up on shore creating a seabreeze. then you still have all of that heat from the day radiating out of the structure you are sleeping in.

i’m currently in a small anchorage where I would love to run my generator at that time of day for about an hour to cool things down but I am concerned that I will disturb others.

[Benz]

Originally Posted by Chotu

i’m currently in a small anchorage where I would love to run my generator at that time of day for about an hour to cool things down but I am concerned that I will disturb others.

I wish everyone was this considerate.

[MicHughV]

This where a big wind scoop comes in handy.
I have one over the forward hatch.
Even a tiny waft of air is enuff to cool perspiration on your skin...enabling sleep...

[Mickeyrouse]

I like and have used wind scoops, but they’re not always practical. A no go in rainy weather, obviously, and in foggy conditions you’re just bringing all that humidity indoors.

[Chotu]

Originally Posted by Benz

I wish everyone was this considerate.

me too. It’s even worse because I have to close up completely due to the particulate air pollution being in the orange/unhealthy level.

and of course there’s an excessive heat warning at the same time. And my boat is built like a greenhouse

Praying my anchor neighbor leaves. But there are still houses pretty close by on shore also.

[boatman61]

Naked...
Mind, I do that in winters as well..

[Mike OReilly]

Oh man, at 32ºC I’m dying. My ideal air temperature is more like 8º to 15ºC. After that, I’m having to peel off covers or run the fan.

[MicHughV]

The key is having bow to stern awnings, besides providing shade over the whole boat, hatches can remain open when it rains.

I also made wind scoop " ears" that fit over an open porthole. They attach with studs around the porthole and extend out to the lifelines where they are attached with a sort length of string.
When it rains, I simply close the porthole, no need to remove the " ear". Once rain has passed, porthole gets open again.
It provides a tremendous amount of air below.
I also have the battery powered mini fan. They run forever, and provide just enuff air to cool you down.

Never had an issue with heat below decks...

[Piscis]

When at anchor, most of the time i am sleeping outside. On the trampoline or some other spot with air flow. When it starts to rain... i move inside and turn on a fan.

In the Marina, i sleep inside with fan on. If it gets too hot, i turn on the A/C.

John.

[s/v Jedi]

With the new LFP battery banks and efficient variable speed drive A/C units (like this one: https://www.hodgesmarine.com/vel2483...condition.html) we can now simply sleep without humidity, heat and mosquitoes

[wingssail]

A single fan over my bed pulling air in though a small hatch really helps.

At anchor there is often some breeze flowing through the boat from a big open hatch forward all the way to the aft cabin where I sleep. Big awnings over the deck and hatches keep the rain out.

In the marina, during the hottest times of the year, I run the air conditioning, but it goes into "energy saving mode" at night. With the fan it is not needed.

But in really hot conditions Judy and I used the following strategy:
We filled a small spray bottle with fresh water and we "misted" each other when we couldn't get to sleep. With the fan blowing quietly over our bare, damp, bodies we were quite comfortable and slept well.