Well, this is complicated. One of the linked studies shows the opposite result claimed in this article. This article says:
"About 60 to 90 minutes before a usual bedtime, the body starts losing core temperature. There’s a physiological explanation for that: when the body is heated, we feel more alert. And conversely, when the body cools down, we tend to feel sleepier. Cooler internal body temperatures are correlated with a rise in melatonin, a hormone that induces sleepiness. A bunch of doctors tested this out by making people wear skinsuits—they kind of look like cycling outfits—that dropped their body temperature just a touch, one or two degrees Fahrenheit, to see if they’d sleep better. They did."
But when I look at the linked abstract, it says:
"By employing a thermosuit to control skin temperature during nocturnal sleep, we demonstrate that induction of a mere 0.4 degrees C increase in skin temperature, whilst not altering core temperature, suppresses nocturnal wakefulness (P<0.001) and shifts sleep to deeper stages (P<0.001) in young and, especially, in elderly healthy and insomniac participants. Elderly subjects showed such a pronounced sensitivity, that the induced 0.4 degrees C increase in skin temperature was sufficient to almost double the proportion of nocturnal slow wave sleep and to decrease the probability of early morning awakening from 0.58 to 0.04. Therefore, skin warming strongly improved the two most typical age-related sleep problems; a decreased slow wave sleep and an increased risk of early morning awakening."
It's worthing noting that the abstract disagrees with the article in two main dimensions: it's only a small change in surface skin temperature, not core body temperature; and the abstract says it's a temperature increase, not a decrease.
I know I experienced the first of those quoted effects.
Every quarter I do a 1500km drive(or actually 3000km given that I drive back and forth), which is now split into two days, but that wasn't always the case - I used to regularly spend 20h+ driving.
Anyway one thing I learned from this is how to recognize if you're likely to fall asleep at the wheel soon: you get cold, even if you weren't before.
Presumably, there is an optimal temperature range for sleeping, and for healthy (not young/elderly/insomniac) adults, that temperature range is slightly below their normal temperature. That corroborates Tade0's comment below - observing that starting to feel cold at the wheel means the driver is in danger of falling asleep.
I've also embarked on long (16 hours at a time) drives, and can confirm starting to feel cold means I'm starting to fall asleep. But what I do next to continue being awake is this - I turn up the A/C. When I'm freezing cold, I can't fall asleep. Similarly, when I'm sleeping at night and the blanket has been ahem, stolen, by the significant other, I wake up from being freezing cold.
So back to the seemingly contradicting data -
>increase in skin temperature... shifts sleep to deeper stages (P<0.001) in young and, especially, in elderly healthy and insomniac participants
Likely, these _ab_normal individuals are past the "comfortably cool" temperature perfect for sleeping and are instead too cold to sleep. Therefore, a thermosuit that negates that effect and brings their temperature back up to at least "comfortably cool" aids these individuals' sleep. The logic behind this also holds for the article's claim that babies (worse at thermoregulation) need more blankets.
I agree with your assessment of the research. But my point is that the linked article does not; it claims that the research used a suit which cools the participants, which is not the case. It, unfortunately, uses an incorrect understanding of the research (a cooling suit) to support a more well-established, true statement (core temperature drops around sleep).
Hmm. I see, you're quite right - they either cited the wrong skin suit study or potentially assumed not too many people will click on "They did [sleep better with cooling suits]."
I wonder if that actually is an agreement, but the actual measurement should be difference between skin and core temperature? So either decreasing core or increasing skin both have the same effect.
"About 60 to 90 minutes before a usual bedtime, the body starts losing core temperature. There’s a physiological explanation for that: when the body is heated, we feel more alert. And conversely, when the body cools down, we tend to feel sleepier. Cooler internal body temperatures are correlated with a rise in melatonin, a hormone that induces sleepiness. A bunch of doctors tested this out by making people wear skinsuits—they kind of look like cycling outfits—that dropped their body temperature just a touch, one or two degrees Fahrenheit, to see if they’d sleep better. They did."
But when I look at the linked abstract, it says:
"By employing a thermosuit to control skin temperature during nocturnal sleep, we demonstrate that induction of a mere 0.4 degrees C increase in skin temperature, whilst not altering core temperature, suppresses nocturnal wakefulness (P<0.001) and shifts sleep to deeper stages (P<0.001) in young and, especially, in elderly healthy and insomniac participants. Elderly subjects showed such a pronounced sensitivity, that the induced 0.4 degrees C increase in skin temperature was sufficient to almost double the proportion of nocturnal slow wave sleep and to decrease the probability of early morning awakening from 0.58 to 0.04. Therefore, skin warming strongly improved the two most typical age-related sleep problems; a decreased slow wave sleep and an increased risk of early morning awakening."
It's worthing noting that the abstract disagrees with the article in two main dimensions: it's only a small change in surface skin temperature, not core body temperature; and the abstract says it's a temperature increase, not a decrease.