When winter approaches, many people cannot go outside without some basic items, such as a jacket, gloves and also a hat. The latter, in addition to being a complement that suits some very well, has also represented a mantra that has been repeated on different occasions: heat ‘escapes’ largely through the head.
There are nuances. This is something that is accompanied by stratospheric figures, such as between 40 and 50% of our body heat ‘escapes’ through the skull. But the truth is that science adds nuances to these data so that we can be much calmer, although in the case of newborns we can have an interesting debate.
The origin. To understand why half the world believes that the head works like a human chimney, you have to travel to the 1970s. And more specifically to the United States Army Survival Manual.
At that time, experiments were carried out with subjects exposed to extreme cold temperatures. The methodological problem, or rather the subsequent interpretation, was that the participants were wearing arctic survival suits that covered the entire body… except the head. Logically, when measuring the heat loss, the researchers found that most of it escaped through the only area that was bare. And from here arose the need to wear a hat because almost all the heat was released from this part.
What is known now. Subsequent studies have been responsible for dismantling this belief. that 40-50% of the heat is released through the skull. The conclusion of science indicates that physical reality is much simpler, since heat loss is proportional to the surface of exposed skin.
In this way, if the head of an adult represents approximately 7% of the body surface, it will contribute only to diffuse 7-10% of body heat that is being lost.
They have proven it again. In addition to the most classic studies that have been done, science has also wanted to analyze this phenomenon in cold water swimmers. using neoprene suitscomparing when their head is submerged and when it is above the water. Here it was seen that the skull does not dissipate heat disproportionately, but is simply exposed skin with nothing special that indicates that it should be protected more than another part of the body.
The cold of the head. Although the percentage of heat lost here is low, there are physiological reasons to protect it. Specifically, the head, and especially the face and scalp, are areas with very little fat or muscle insulation compared to other parts of the body. In addition, they have a large number of blood vessels and thermal receptors on the surface, which makes them much more sensitive to the sensation of cold.
This means that, although 50% of the heat is not lost through the skull, cooling the head gives us greater thermal discomfortso by covering it we feel much warmer. In addition, it also acts on cardiovascular reflexes and lowering core temperature.
Therefore, wearing a hat in winter is useful, but it works the same as wearing gloves or a good scarf: it is another layer of insulation, not a magic cap.
An exception. There is always an exception to every rule, and in this case they are in babies. in a newbornthe head is enormous in proportion to the rest of the body, occupying a much greater percentage of body surface than in an adult. This means that they do lose more heat here than in any other part of the body, and that is why we always see a baby with a hat on almost from the time they are in their first days of life.
Science has pointed out Because in full-term newborns, an insulating hat can reduce total heat loss by 75% and oxygen consumption by 85% compared to being naked. In low resource settings or in low weight babies, the use of wool hats is clearly associated with a lower incidence of hypothermia.
But with control. In healthy, full-term babies who are in warm rooms, or practicing the skin-to-skin method, the evidence suggests that the hat does not always provide a clear extra benefit and even, if combined with excessive warmth, it can promote overheating.
With or without a hat. In conclusionit must be taken into account that the head is not a special part where a large amount of heat is released. However, in everyday life it is usually the only part of the body that we wear naked in winter and it has little natural insulation, so covering it is an efficient strategy to improve thermal comfort.
Images | Jonathan J. Castellon
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