Do You Get Sick More Often in Cold Weather?

Yes, your abuela was right. You’re more likely to get sick during winter — and now, at last, we have a study that explains the biological reason why.

The study, published in The Journal of Allergy and Clinical Immunology, shows that our immune response is affected by colder temperatures and that the germ-fighting cells in our noses – often our first line of response to the threat of a virus – don’t battle the intruder as well when the temperature drops.

“We’ve long known that [respiratory] illnesses are more common in winter,” says Jose Ruiz, M.D., an otolaryngologist with the University of Miami Health System. “We have many theories on this. For example, people are spending more time indoors and in close proximity. But in the end, we didn’t really have evidence of how and why this happened.”

Now physicians do. The journal study, Dr. Ruiz says, is important because it points to the reason, at a molecular level, why those pesky winter spikes of illnesses are so common.

In a nutshell: cold air short-circuits our immune response.

In fact, a drop of just 9 degrees Fahrenheit (or 5 degrees Celsius) inside our nose can cut our virus-fighting capabilities almost in half.

To recognize how this happens, we must understand the battle going on in our nasal cavities when an intruder enters.

As we breathe in a virus or bacteria, “cells [in our nostrils] recognize it and immediately begin their anti-viral activity to fight the infection,” Dr. Ruiz says.

They do so by producing small packages called extracellular vesicles, or EVs, specifically designed to kill the virus. These EVs act as decoys, so the virus sticks to them instead of the actual lining of the nose. We then expel these bound viruses before they have a chance to do any serious harm.

Think of these EVs as the foot soldiers of our initial immune response.

They’re effective and numerous.

They ambush.

The study found that the nose increases the production of these extracellular vesicles many times over when an intruder first invades.

In addition, these nasal EVs contain more anti-viral micro RNA sequences than normal cells, which gives them Marvel Universe-like superpowers. That’s because micro RNAs comprise another round in the germ-fighting arsenal.

A chill in the air, however, limits all that micro-RNA activity. “You reduce your immune system’s ability to fight off the virus,” Dr. Ruiz says.

While the science is fascinating, it doesn’t mean we’re totally defenseless against the viruses and bacteria living all around us.

Dr. Ruiz has several common-sense suggestions to keep the coughing and sneezing at bay during sweater weather:

• Avoid close contact with people who are sick. If you’re the one sniffling and hacking, be courteous and wear a mask when you’re around others.
• Wash your hands.
• Don’t touch your face. You never know what you’ve picked up on a countertop or handrail.
• Get enough sleep. “Several studies have shown that if you get less than seven hours of sleep, you’re at a higher risk of getting sick,” Dr. Ruiz says.
• Limit stress. Your immune system is less effective when your psychological stress level is high.
• Eat healthy and exercise. One small study of 1,000 people in the British Journal of Sports Medicine found that staying active halved the odds of catching cold viruses or made the infection less severe.

Ana Veciana-Suarez is a regular contributor to the University of Miami Health System. She is a renowned journalist and author who has worked at The Miami Herald, The Miami News, and The Palm Beach Post. Visit her website at anavecianasuarez.com or follow @AnaVeciana on Twitter.

Tags: apoptotic bodies, cold weather, common cold, Dr. Jose Ruiz, health care in Miami, plasma membrane