In A Nutshell
It’s an oft-repeated fact that viruses, not cold weather, make you sick. Research shows, though, that the cold is involved as well. Yale scientists found that when the temperature of your nasal cavity and upper respiratory system drops only a few degrees, it seriously compromises your immune system’s response time to any viruses you might inhale. Not only are fewer defenses sent out by your system, but cells are slower to kill themselves when they become infected. So the cold weather might be helping to make you sick, just like Mom always said.
The Whole Bushel
We’re pretty sure it’s a scene that’s played itself out countless times. You’re heading outside in the winter, and a parent reminds you to dress warm so you don’t catch a cold. You smugly respond that germs cause colds, not the cold itself, then head out into the frosty air sans hat and with your jacket unzipped, confident that no germs are going to come get you because of it.
Science, though, has weighed in again, and the results are firmly in Mom’s corner.
The debate on how cold weather relates to actually catching a cold has been one that’s been raging ever since the first old wives told their tales of buttoning up so you don’t get sick. Actual scientific experiments have had some strange results, but Yale researchers think they’ve finally cracked it.
In a study presented to the American Society for Microbiology, they showed there was a definite relationship between the outside temperature and how susceptible a person is to the rhinovirus, which causes the common cold. There are countless different types of the virus, but they found that there’s a definite correlation between how cold it is and the body’s natural defenses against the virus.
They found that the colder it gets, the less capable the body is at defending against the common cold.
The research team took a look at mice and how they reacted to a mouse-only sort of rhinovirus. When the animals exposed to the rhinovirous were in warm temperatures, their bodies naturally reacted by sending a quick signal to their immune system, which responded just as quickly with all the naturally produced siege weapons the mouse needed to fight off the incoming virus. The lower the outside temperature got, though, the slower the body was to react to the virus and the fewer defenses the immune system sent out.
The second part of the study looked at how the cells themselves dealt with the warm weather vs. the cold weather. Researchers did this one on human cells and found that in cold environments the cells weren’t as quick to kill themselves once they were infected by a virus. The process of cell suicide is one that’s designed to kill the cell and the virus and to prevent the spread of illness.
Specifically, the cells that were impacted by the cold the most seemed to be the cells of the upper respiratory system and the airways. When those areas—the first line of defense against a cold—reached only about 33 degrees Celsius (91.4 °F), the immune system was incredibly compromised.
And that’s not a huge jump. The researchers also noted that when compared to our core temperature, which is usually a warm and toasty 37 degrees Celsius (98.6 °F), the temperature of our nasal passages is typically colder at around 33–35 degrees Celsius (91.4–95 °F). That means that it doesn’t take much to lower the temperature of your respiratory system to a point where your immune system is firing at a reduced rate. When the outside temperature drops into a range where snow, sleet, and freezing rain are going to happen, you’re well below that threshold.
That’s all in line with what we’ve known about cold viruses since around the 1960s: that they’re more likely to thrive in the nasal passages than in the lungs and that there’s a reason you should listen to your mother.