US scientists may have found the biological reason why we get more respiratory diseases in winter than at other times of the year. It turned out to be due to the cold air itself. It impairs our body's defenses.
Reducing the temperature in the nose by just five degrees Celsius kills nearly 50 percent of virus- and bacteria-fighting cells in our nostrils, according to the study published in the Journal of Allergy and Clinical Immunology ("JACI").
A virus or bacterium usually enters the body through the nose. The tip of the nose then recognizes the germ immediately, long before it is recognized by the nose itself - i.e. by the main part of our olfactory organ - according to one of the research results.
At this point, the defense cells permanently present in the nose begin to create billions of copies of themselves. These are called extracellular vesicles, or EV for short. "EVs can't divide like other cells, but they behave like little mini versions of cells that have been specially designed to kill viruses," explains Dr. Benjamin Bleier, director of the ENT department at the Massachusetts Eye and Ear Institute. "EVs act as decoys, so if you inhale a virus, that virus will stick to those decoys instead of entering your body."
When attacked, the nose increases EV production by about 160 percent, the study found, making it well-armed for common viruses and bacteria under average temperatures. However, if the temperatures drop to just above freezing, things look different.
To simulate this, the research team exposed four study participants to temperatures of around four and a half degrees Celsius for 15 minutes and observed their nasal cavities. "We found that when exposed to cold air, the temperature throughout the nose can drop by up to five degrees Celsius." This is enough to knock out the tip's immune advantages, explains Bleier. 42 percent of the EV was lost in this cold.
Actually, our immune system has the talent to react consistently effectively to most dangers and viruses. But now, for the first time, it has been possible to show that this talent appears to be restricted in colder temperatures, says ENT specialist Prof. Dr. Stanford School of Medicine's Zara Patel speaks to CNN about the research findings.
In the future, Bleier expects to develop drugs that build on this discovery. These new drugs will "essentially trick the nose into believing it has just discovered a virus," says Bleier. The ambient temperature of the people being treated would then play only a minor role in the success of the treatment.
Sources: "JACI", CNN
