Heat loss from the head in cold weather
In exposing the "myth" that 40 -50% of body heat is lost through the
head in cold weather (1) the authors conclude that the body should be
protected but that it is a matter of individual preference whether or not
to cover the head. This appears to be too cavalier a statement to go
unchallenged, particularly in the case of elderly people exposed to cold
weather conditions. As the main channel of convective and radiant heat
loss when the body is well insulated, exposure of the head and face can
account for a large proportion of body heat loss. It is, of course, a
different matter when the body and head are immersed in water, as in the
experiments quoted, when a measured 10% of total surface heat loss occurs
from the head. The claim that there is nothing special about the head in
heat balance ignores the important influence of facial cooling in air on
systemic cardiovascular reflex responses (2) and that body temperature can
be selectively influenced by cooling of the head and face. Covering these
areas with hat and muffler in cold weather should remain part of the
recommendations designed to help reduce winter morbidity and mortality.
1 Vreeman R, Carroll A. Seasonal medical myths that lack
convincing evidence. BMJ 2008 ; 337 : a2769 (20-27 December).
2. Collins KJ, Abdel-Rahman TA, Easton JC, Sacco P, Ison J, Dore C.
Effects of facial cooling on elderly and young subjects : interaction with
breath-holding and lower body negative pressure. Clin Sci 1996 ; 90 :
485 - 492.