Most people believe that sleeping in a cold room can directly cause them to catch a cold or the flu. This common idea links the physical sensation of coldness with the onset of illness symptoms. Scientific understanding, however, separates environmental temperature from the actual mechanisms of infection. While temperature does not cause sickness, it can influence your susceptibility to illness and your overall comfort.
The Real Cause of Illness: Pathogens, Not Temperature
Infectious illnesses like the common cold and influenza are caused by specific microscopic invaders, viruses and bacteria, known as pathogens. Temperature alone cannot spontaneously generate a virus or bacterium inside the human body. Catching a respiratory illness requires exposure to these pathogens, typically through airborne droplets or contaminated surfaces.
The belief that cold air causes a cold is a misunderstanding rooted in the seasonal timing of these diseases. People spend more time indoors and in closer proximity during colder months, which facilitates the transmission of respiratory viruses. The presence of a pathogen is the prerequisite for an infectious illness to take hold. Without a virus or bacterium, a person cannot contract a cold, regardless of the room temperature.
How Cold Environments Affect Immune Response
While cold air does not cause a viral infection, it can temporarily compromise the body’s first line of defense against pathogens. The nasal passages are the primary entry point for viruses. When you breathe in significantly cooler air, the temperature inside your nose drops.
This localized temperature decrease can impair the innate immune response in the nasal cavity. Nasal cells release tiny fluid-filled sacs called extracellular vesicles (EVs) into the mucus, which act as decoys for viruses and contain antiviral proteins. Studies show that a drop in nasal tissue temperature can reduce the release of these protective EVs by nearly 42% and compromise the function of their antiviral proteins. This blunted response makes it easier for an inhaled virus to bind to nasal cells and initiate an infection.
Beyond Infection: Non-Infectious Health Effects of Cold Air
Sleeping in a very cold room can trigger non-infectious symptoms and exacerbate existing respiratory issues. Cold air naturally holds less moisture, leading to a dry environment that can irritate the mucous membranes of the nose and throat. This dryness can result in a sore throat, nasal congestion, or a dry cough upon waking.
For individuals with pre-existing conditions like asthma or Chronic Obstructive Pulmonary Disease (COPD), cold air exposure can be problematic. Inhaling cold air can cause the airways to narrow, potentially triggering bronchoconstriction, leading to shortness of breath or wheezing. Very low temperatures can also cause muscles and joints to stiffen, which may worsen discomfort for people with arthritis or fibromyalgia.
Setting the Ideal Sleep Environment
For most adults, a cooler bedroom temperature is beneficial for sleep quality. The body’s core temperature naturally drops when falling asleep, and a cool room supports this physiological signal. Experts recommend setting the thermostat between 60 and 67 degrees Fahrenheit (15 to 19 degrees Celsius) to promote deeper, restorative sleep cycles.
If your room is at the lower end of this range, or if you live in a dry climate, managing humidity is important to prevent respiratory irritation. Using a humidifier to maintain a relative humidity between 40% and 60% can counteract the drying effect of cold air. Instead of overheating the room, use appropriate bedding and sleepwear to maintain comfort. Layering blankets allows for easy thermal regulation throughout the night.