Gloves?
Check. Hat? Check. Thermal layers? Check. But why am I the only one prepared
for the onslaught of a snowstorm? The cold affects everyone differently.
With Halloween now firmly
behind us, we find ourselves on the slippery slope into full-blown winter.
While many of us may enjoy spending time outdoors on a crisp winter day, few
people enjoy feeling cold.
Our ability to sense
temperature changes is essential to our survival. Small changes to our core
temperature can have detrimental effects, putting us at risk of heat stroke in
the summer or hypothermia in
the winter.
To
retain a steady core body temperature, our bodies have developed sophisticated
mechanisms to sense and respond to temperature fluctuations.
Nerves in our skin are
our first line of defense. They pick up changes in temperature and pass this
information to the brain.
Yet our perception of
cold is very subjective. Why do some people start to shiver at the mere thought
of plummeting temperatures, while others pile on the warm layers only
reluctantly?
What happens when we
get cold?
Once the brain has been
informed of a drop in temperature, it sends signals to our blood vessels to
restrict blood flow to the skin.
John Castellani, Ph.D.,
and Andrew Young, Ph.D. — both from the Thermal and Mountain Medicine Division
of the U.S. Army Research Institute of Environmental Medicine in Natick, MA
— explain that this process of vasoconstriction
prevents further heat loss and protects the body core.
Vasoconstriction
in the fingers and toes is a feeling that many are likely to be familiar with
while reaching for gloves and thick socks.
On top of limiting blood
flow to the skin, we start to shiver. These involuntary, rhythmic muscle
contractions kick out heat to warm our bodies.
These physiological
responses are hardwired into our system but vary from person to person. So,
what influences how we respond to the cold?
Body shape
Size really does matter
when it comes to the cold. The larger a person's body surface area is, the more
heat they lose.
This is closely tied to
the size of subcutaneous adipose tissue, or the fat beneath the surface of our
skin. Fat is a great insulation material. The more subcutaneous fat a person
has, the better their insulation is.
The
difference between how men and women respond to the cold is partly due to body
shape.
Let's take a man and a
woman with the same body mass and comparable surface area. Because the woman
will likely have more subcutaneous fat, she will be better insulated against
the cold.
If we compare this
scenario with a man and a woman with the same amount of subcutaneous fat, the
woman is likely going to have a greater surface area but smaller body mass and
will lose heat more quickly.
Sex and age
However, sex does have a
part to play when it comes to our extremities, where vasoconstriction is more
pronounced in women. In fact, there is evidence from a large study involving twins to suggest that cold
fingers and toes are, in part, determined by our genes.
Fluctuations
in hormones also contribute to how we feel the cold. Women's responses to cold
vary during their menstrual cycles. In men, higher testosterone levels
may reduce sensitivity
to the cold by desensitizing one of the main cold receptors, TRPM8, in the
skin.
Women are more likely
than men to develop Raynaud's disease, which
leaves those affected with mostly cold fingers or toes when temperatures drop.
The exact causes of Raynaud's
disease are unknown.
From around the age of
60, the ability of our bodies to conserve heat and sense the cold starts to
decline.
Seniors also don't start
to shiver until the temperature is much lower, compared with their younger
counterparts, and they also have trouble warming up.
How to get used to
the cold
When our bodies are
repeatedly exposed to cold temperatures, they eventually adjust — that is, if
you don't have Raynaud's
disease. But we are not talking about popping outside for 5 minutes
once per day while spending the rest of our time cuddled up to the heater.
Many
residents living in polar regions have a less pronounced response to cold, Drs.
Castellani and Young explain. They still shiver and restrict blood flow to the
skin, but to a lesser degree.
There are two other ways that
the body can adjust to plummeting temperatures: by increasing either metabolic
heat generation or heat conservation.
How an individual will
react to repeated cold is possibly down to the extent of the heat loss from the
body, but there is still much that researchers don't know about how our bodies
sense and adapt to cold temperatures.
So, if you tend to feel
the chill, you could try spending time outside to build up a tolerance. Or,
reach for your gloves and layer up to keep the cold at bay.
However you choose to
deal with the inevitable onset of winter, we hope you enjoy your time outdoors.
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