How Cold Air Impacts Asthma
About 40% of asthmatics say cold air triggers their asthma.1 These attacks can be even worse when you’re exercising in cold air. So, why is this? Here’s what to know about cold air and asthma.
Why does cold air trigger asthma?
Cold air holds less water than warm air. So, cold air tends to be drier than warm air. 2 So, not only can it cool airways, but it can also dry them. It’s this combination of cooling and drying of airways that is suspected of triggering asthma symptoms.
Our normal body temperature is 98.7°F. Airway cells, like all cells, contain a certain amount of fluid. This is needed so they can do their work. 3 Cells lining airway are also covered by a layer of fluid.4 So, this is the normal state of things inside your airways. Your body is constantly making efforts to maintain this state of normalcy.
Inside your nose are turbinates. These are bony-like protrusions on either side of your nasal passages. These act as natural heaters and humidifiers. They warm and humidify air you inhale to body temperature. So, your nose has a significant job in maintaining normalcy inside your lungs. 5
It’s easy for your nose to keep up when inhaled air is warm. But, when the air gets cold, they have a hard time keeping up. Fluid lining airways is absorbed to humidify cold air. Likewise, cells lining airways also have to get involved. They have to give up some of their moisture to humidify this air. They also have to give up some of their heat. So, inhaling cold air both cools and dries airways. 4
This can happen if the air gets cold enough. It can happen in freezing temperatures. Although this effect is exacerbated (made worse) when you’re exercising in colder temperatures.
How does exercising trigger asthma?
When exercising we breathe in and out rapidly. It gets to the point our turbinates cannot keep up. Making this worse is when we revert to breathing. Many of us breathe through our mouths when exercising. This is because our mouths offer less resistance to inhaled air. Mouth breathing makes breathing easier.
Of course, when you’re doing this your nose is bypassed. Cold and dry air cannot be properly warmed and humidified. Airway cells have to work overtime to warm and humidify this inhaled air. Such rapid changes inside cells cause them to release mediators of inflammation, such as histamine and leukotrienes. These mediators cause airway inflammation.
Of course, asthmatic airways are already somewhat inflamed. So, sensory neurons (nerves) in airway tissue are already sensitized; they are already hypersensitive. They respond by causing smooth muscles wrapped around airways to spasm and constrict. This causes airways to become abnormally narrow.4-6
When this happens, it’s diagnosed as Exercise Induced Asthma (EIA). This is something that affects over 80% of asthmatics. 5-7
Exercise can trigger asthma at any time. But, as the air gets colder, this risk increases. There is no set temperature listed in literature where your risk for EIA starts to increase. Based on my own experience with this, I tend to go with 50°F. If it’s warmer than 50°F I exercise outside if I want. If it’s less than 50°F I exercise indoors. I work out at home or at the health club.
Can non-asthmatics experience this?
If it’s cold enough outside, even non-asthmatics CAN experience asthma symptoms. This is most likely to occur if they are exercising in cold air. The cold air can irritate airways and cause airway inflammation. This inflammation irritates nerves which in turn trigger bronchospasm. When this happens in non-asthmatics, it’s diagnosed as Exercise-Induced Bronchospasm (EIB).
This appears to be a common problem for winter athletes. Those most likely affected are cross-country skiers. In fact, the risk of EIB in cross-country skiers is quite common. So common, in fact, that some researchers even list Cross-Country Induced Asthma as a subgroup of asthma.
Sometimes you will see EIA and EIB used interchangeably. Researchers studying asthmatics tend to refer to it as EIA. Those studying winter athletes prefer to refer to it as EIB. Some authors now refer to both as EIB. So, this should explain why you hear both acronyms being used. They basically mean the same thing.
Can cold-air induced asthma be prevented?
You certainly can make efforts to prevent it. If it’s cold outside you can stay indoors. When you do go outside, place a scarf or mask over your mouth and nose. This allows you to re-breathe some of your warm and humidified exhaled air. It’s also a good idea to exercise indoors when it’s cold. As noted above, I exercise indoors when it’s less than 50°F. Obtaining good asthma control is also a means of preventing, or reducing the effects of, cold air-induced asthma and EIA.
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