How Do Asthma and COPD Differ?
Asthma and COPD are similar diseases. They both are obstructive airway diseases. They both cause similar symptoms. They are both treated with inhalers. But, there are also some key differences between these two diseases. So, how do they differ? Here’s what to know.
Asthma and COPD both have airflow limitation in common. This airflow limitation is caused by airways that become obstructed. When airways are obstructed, this limits the flow of air through them. This is referred to as airflow limitation. The degree of airflow limitation determines how short of breath a person becomes.
So, they are both categorized as obstructive airway diseases. They both cause airflow limitation. And, as noted, they are both treated with similar medicines.
How asthma and COPD differ
Asthmatics tend to only have airflow limitation during flare ups, which are usually referred to as asthma attacks. These attacks are reversible with time or treatment. So, between attacks, lung function should be normal or close to normal. Therefore, asthmatics are usually only short of breath during asthma flare-ups.
COPD also presents with airflow limitation. However, unlike asthma, it tends to cause some degree of airflow limitation all the time. So, this this means that symptoms may always be present to some degree.
Also unlike asthma attacks, COPD flare-ups are only partially reversible with time or treatment. So, between flare-ups, lung function remains low. Therefore, COPDers may experience some degree of shortness of breath between flare-ups.
This is where the “Chronic” comes from. This is why it’s referred to as “Chronic Obstructive Airway Disease.” This is opposed to a simple “Obstructive Airway Disease.”
Other key distinctions
Asthma is caused by an overactive immune response
Researchers think this is due to asthma genes. These genes tell immune cells to recognize otherwise innocuous (harmless) substances in the air as harmful. These immune cells initiate an all out assault on these substances. This results in the release of chemicals that cause airway inflammation. This inflammation is what causes asthma symptoms.
COPD is caused by chronic exposure to noxious chemicals
Day after day after day after day exposure to these noxious chemicals irritate airways. This initiates a response from the immune system. Mediators are released to get these chemicals out of the lungs. These "mediators" cause inflammation of airways and other lung tissue. This is what causes chronic bronchitis and emphysema. Unlike asthma, both of these diseases are progressive, meaning they may slowly get worse over time.
The type of inflammation may be different for both
Asthma inflammation tends to be eosinophilic. This type of inflammation responds well to corticosteroids. Asthma is also reversed with medicines that dilate airways. So, bronchodilators called beta 2 adrenergics are also helpful. Often, combination inhalers provide both types of medicine. These may help asthmatics obtain good control of their disease. This means they should be symptoms free on most days.
COPD causes chronically obstructed airways
This may be due to airways that are drawn taught due to emphysema. It may be due to airway inflammation. This inflammation may be eosinophilic such as in asthma. This may be reversible with corticosteroids. But, inflammation may be neutrophilic and less responsive to corticosteroids. COPD inflammation may also respond to another type of bronchodilators called muscarinics. There are other treatments to help allay symptoms and slow the progression of the disease.
How doctors differentiate the two
Doctors can usually differentiate the two by asking you questions. Do you have a family history of asthma? COPD? Do you smoke? Did you have a job that exposed you to dust, fumes, or chemicals. When do you have symptoms? How often? They may also perform tests. The best test is a breathing test called a PFT. This is a test that measures your lung function. If lung function improves after using a bronchodilator, this usually indicates asthma.
What to make of this? There are certainly other differences, other than those listed here There are also asthmatics diagnosed with severe asthma. They may present similarly to COPD. There are also those who have a combination of both, Asthma-COPD Overlap Syndrome. There is also a lot more to learn about both.
Do you have questions about your COPD diagnosis?