As winter starts to grip the Northern hemisphere, it's time to wrap up. But not everyone perceives the cold the same way.
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?
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.