COPD vs asthma: what’s the difference?
Asthma and COPD are both long-term conditions that affect the airways and lungs, making it difficult to breathe. Distinguishing between the two can be difficult and some people have signs and symptoms that are characteristic of both illnesses. However, an accurate diagnosis is crucial for providing the most appropriate treatment and management.
What is asthma?
Asthma affects about 358 million people globally. In the USA, about one in 12 adults are diagnosed with the condition.
With asthma, the inner lining of your airways is sensitive, becomes inflamed and swollen and produces excess mucus. In addition, the smooth muscle surrounding the airways tightens. It results in the airways becoming narrower – a process called bronchoconstriction – making it difficult to breathe in and out.
What is COPD?
COPD describes a group of lung conditions – including bronchitis and emphysema – that cause our airways to become narrowed, making it difficult to breathe out.
Worldwide, about 384 million people have COPD, though many remain hidden and undiagnosed. This is partly because COPD develops slowly over many years, which means for many that they don’t notice any symptoms until they reach around their 50s.
Key differences between asthma and COPD
Airway narrowing is a feature of both COPD and asthma. In both conditions, symptoms can flare up and worsen suddenly – this is called an exacerbation. However, the processes involved are different as follows.
Causes and triggers
|In COPD the damage is caused by breathing in harmful, irritant substances in the air, often over a long time.
The most common irritant is cigarette smoke – up to three-quarters of people who have COPD smoke or used to smoke. Other causes of COPD include air pollution, workplace dust, and chemicals.
Flare-ups are commonly triggered by a respiratory infection, especially in the winter.
|Asthma is an inflammatory, allergic response. We don’t know the exact cause but it’s likely a combination of environmental, genetic, and occupational factors.
Flare-up triggers vary from person to person and can include laughter, exercise, respiratory infection, allergy (e.g. to pollen or mold), and the weather.
Chronic respiratory symptoms common to asthma and COPD include breathlessness, cough, chest tightness, and wheeze. However, the pattern of symptoms varies.
In COPD, breathlessness is present most days and makes physical activity difficult. It may be associated with a cough and phlegm. Usually, COPD symptoms worsen over time.
Asthma symptoms vary over time and in intensity. There can be long symptom-free periods.
Symptoms improve spontaneously or with inhaled bronchodilator/corticosteroid treatment.
|COPD is rare in people under 40.
||Asthma is common in childhood but can start at any age. Some children with asthma find that their symptoms improve as they get older.
Lung function test (spirometry)
A lung function test is a simple breathing test that measures how well your lungs are working. You’ll be asked to blow hard into a machine called a spirometer that measures the total volume of air that you can breathe out in one go, and how quickly you can empty your lungs of air. People with healthy lungs can empty at least 70% of the air in their lungs in the first second of a hard exhale – this measurement is called the forced expiratory volume in 1 second (FEV1). A reduced FEV1 score confirms you have airway obstruction – the lower your score, the greater the level of obstruction.
|People with COPD have persistent airways obstruction. It’s not usually reversible with treatment. Lung function tends to deteriorate over time.
||People with asthma usually have variable airways obstruction. It can vary depending on how well-controlled their asthma is.
With well-controlled asthma, lung function can be retained.
Common lifestyle advice includes stopping smoking, staying healthy, eating well, and appropriate physical exercise.
Many of the asthma medications and COPD medications are the same, such as bronchodilators and anti-inflammatories delivered using an inhaler device and/or taking a tablet. However, the two conditions have quite different treatment plans.
|When you are diagnosed with COPD, the first-line drug treatment is usually a bronchodilator inhaler. Your doctor might add in an inhaled corticosteroid later if that’s not enough.
||With an asthma diagnosis, you’ll be prescribed an inhaled corticosteroid straight away. This is essential to reduce your chance of having a severe, possibly life-threatening flare-up.
Might I have both asthma and COPD?
Combined asthma plus COPD – sometimes called ‘asthma-COPD overlap’ – is not a separate condition. However, it is possible for a person to have both asthma and COPD at the same time. It is not clear how often this happens and different studies have reported that anywhere between about one-tenth and one-half of people with either asthma or COPD might have both conditions. Rates vary widely depending on how old you are, your gender, and how the researchers set up their study.
Even though COPD is uncommon in people aged under 40 years, the combined symptoms of asthma plus COPD may appear in childhood or early adulthood.
More studies are needed on people with both asthma and COPD. However, we do know that people who experience a mixture of asthma-type and COPD-type features often experience more troublesome symptoms and flare-ups. They also tend to need more healthcare support and their lung function worsens more quickly than for people who have either asthma or COPD alone.
How will I be treated if I have both asthma and COPD?
In the first instance, your doctor will treat your asthma. You’ll be prescribed an inhaled corticosteroid to reduce your chance of having a severe or life-threatening asthma flare-up, and they will probably add in a bronchodilator later. Depending on how mild or severe your COPD-type symptoms are, you may need more COPD drug and non-drug management as well.
Your doctor will review your symptoms, treatment, and how well you are within two or three months of treatment. You may need to see a hospital specialist if there’s still uncertainty about your diagnosis or if your symptoms have not improved adequately.
Can asthma lead to COPD later?
Not everyone with asthma goes on to develop COPD. However, having asthma as a child or younger adult can affect how well your lungs develop, and that can increase your chances of having COPD when you’re older. One recent study reported that over one in 10 children with persistent asthma (i.e. they had symptoms every day) went on to have COPD as a young adult.
This means that if you have asthma, it’s even more important that you don’t smoke. Quitting will help to lower your chance of developing COPD in later life as well.
Learn more about:
American Lung Association 2020.
BLF 2020. Asthma in children.
GINA 2020. Online Appendix.
Halpin DMG. 2020. What is asthma chronic obstructive pulmonary disease overlap? Clin Chest Med 41 (2020) 395–403.
NICE 2018 (updated 2019).