Summer Days... Heat, Humidity and an Asthmatic Body
Summer days bring lots of good things, sweet delicious watermelon, bike rides, being physically active outdoors. Asthmatics need to be aware that hot days, may also be humid days. It is important to keep an eye on heat and humid days. People with chronic illness may be at greater risk from extreme heat. These include older adults over 65 years of age, infants and young children and those with chronic heart and lung disease which includes us asthmatics.
There are two ways to look at this in North America. One is the Humidex which is short for humidity index, it is thought be a Canadian innovation that was first used in 1965 as toothed by Environment Canada. While has been considered not a perfect system, it helps grasp a picture of what the temperature outside feels like. The premise of the index is based on a calculation of heat and humidity, it used the current air temperature and dew point. Dew point is the temperature ad barometric pressure that vapor will condense into liquid.2
Why do heat and humidity affect asthma?
It matters because humidity can wreak havoc with our natural air conditioning system, our body! This is such a great analogy by David Phillips, Environment Canada's senior climatologist. Our natural air conditioning works is when we perspire, that moisture in our skin evaporates into the air and that takes away some of the heat from our body.3
Did you know that our bodies try to maintain temperature of 37 C and that sweating in the summer helps cool us down. Unfortunately, when humidity is too high and the air is saturated with moisture, sweat evaporations stops. Your body temperature can rise and a number of potential heat-related problems. The opposite is also true, in conditions in which the relatives humidity is lower, our bodies feel cooler.4
In the US the term heat index is used. which refers to the air temperature with the relative humidity factored into it. This provide a temperature of what it "feels like" or apparent temperature, this is the temperature with the humidity factored in. There is a complex calculation that is used to predict these temperatures. The National Weather Service also has a calculator tool that also makes life much easier. There is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (decrease), the heat index increases (decreases). 4
Protecting yourself in the heat and humidity
It is important to keep an eye on temperature and humidity. These also go hand and hand with air quality index. The major pollutants that can affect asthma are ozone that is found in fog and particle pollution, which can be found in haze, smoke and dust. When ozone and particle pollution are in the air, adults and children with asthma are more likely to have symptoms.2 It is important to avoid risk of exposure to triggers on these days. It is also important to stay hydrated and prevent overheating. Many weather services and health departments issue alerts when conditions in your area pose a risk to those with chronic illness. This may mean that you may have to stay inside in the air-conditioning for cooler environments.
How does your asthma change with the seasons?