When winter approaches, many people cannot go outside without essential items, such as a jacket, gloves, and a hat. The latter, aside from being a stylish accessory, is often associated with a long-standing belief: that heat ‘escapes’ largely through the head.
Understanding the Myths
There are nuances. Claims suggesting that between 40% and 50% of our body heat escapes through the skull have circulated widely. However, scientific insights reveal a more nuanced perspective on this topic, particularly when discussing newborns.
The Historical Context
The origin. To grasp why many people believe that the head acts as a thermal chimney, we must look back to the 1970s and specifically examine the U.S. Army Survival Manual. During that era, experiments involved subjects exposed to extreme cold wearing arctic survival suits that covered their bodies but left their heads exposed. Naturally, scientists found that heat loss was most significant in the only uncovered area—leading to the conclusion that most heat escapes from the head.
Modern Findings
What is known now. Subsequent studies have challenged the earlier belief that a majority of body heat dissipates through the head. Current scientific consensus indicates that heat loss is directly proportional to the area of exposed skin. Since the head accounts for approximately 7% of an adult’s body surface, it contributes to only 7-10% of total body heat loss.
Scientific Dissection
They have proven it again. Examination of cold water swimmers has further shown that the head does not disproportionately lose heat compared to other body parts. Research involving neoprene suits illustrated that exposure or submersion of the head in water didn’t yield significant heat loss differences than those observed in other areas of the skin.
Physiological Concerns
The cold of the head. While the percentage of heat loss from the head is low, there are physiological reasons to keep it warm. The head, particularly the face and scalp, lacks much fat or muscle insulation compared to other body parts, making it more sensitive to cold. This heightened sensitivity can lead to the perception of feeling colder when the head is exposed.
Though it’s inaccurate to say that most heat escapes through the skull, covering the head helps us feel warmer and can aid in regulating core body temperature and cardiovascular reflexes, just like wearing gloves or a scarf does.
Exceptions to the Rule
An exception. One notable exception is in newborns. Due to their proportionally large heads, infants can lose more heat through this area than older children or adults, which explains why they are often seen wearing hats from a young age. Research shows that for newborns, the usage of insulating hats can significantly reduce heat loss and oxygen consumption.
In low-resource settings or particularly for low-weight babies, using wool hats correlates with lower rates of hypothermia.
Conclusions
With or without a hat. In summary, while the head is not a primary source of heat loss, it remains crucial to protect it due to its lack of natural insulation and high heat sensitivity, which significantly impacts thermal comfort in cold weather. Thus, wearing a hat in winter is practical and effective but should be viewed as one component of overall warmth rather than a standalone solution.
Images | Jonathan J. Castellon