Presumably, there is an optimal temperature range for sleeping, and for healthy (not young/elderly/insomniac) adults, that temperature range is slightly below t

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.