Asthma is not considered COPD. They are two separate respiratory conditions with different causes, different patterns of inflammation, and different long-term effects on the lungs. However, the two can look similar on the surface, and roughly 2% of the general population has features of both conditions at the same time, a situation called asthma-COPD overlap.
Why Asthma and COPD Are Different Conditions
The core distinction comes down to what happens inside the airways and whether the damage is reversible. In asthma, the airways narrow in response to triggers like allergens, exercise, or cold air, then open back up, either on their own or with medication. In COPD, the airways are permanently narrowed and the lung tissue itself is damaged. This is why a breathing test called spirometry is central to diagnosis: after inhaling a medication that relaxes the airways, a person with asthma will show significant improvement in airflow (at least a 12% increase and 200 mL gain in the volume of air they can force out in one second). A person with COPD will not show that same bounce-back.
The type of inflammation also differs at a cellular level. Asthma involves a surge of eosinophils, a type of white blood cell tied to allergic reactions, along with immune cells that drive episodic tightening of the airways. COPD involves a buildup of neutrophils and macrophages, immune cells more associated with long-term tissue damage. In COPD, enzymes from these cells gradually break down the elastic fibers in the lungs, destroying the tiny air sacs where oxygen enters the blood. This destruction is irreversible.
Differences in Symptoms and Timing
Asthma often starts in childhood, though it can appear for the first time at any age. Symptoms tend to come and go: wheezing, chest tightness, shortness of breath, and coughing that vary in intensity from day to day or week to week. Many people with asthma have long stretches where they feel completely fine.
COPD typically appears after age 40 and is strongly tied to a history of smoking, usually 10 or more pack-years (the equivalent of smoking a pack a day for 10 years). Symptoms are more constant: a persistent cough, frequent lower respiratory infections, and breathlessness that gradually worsens over time rather than flaring and resolving. Exposure to occupational dust, indoor pollution, or outdoor air pollution can also cause COPD, as can a genetic condition called alpha-1 antitrypsin deficiency, where the body doesn’t produce enough of a protein that protects lung tissue.
People with alpha-1 antitrypsin deficiency are sometimes initially diagnosed with asthma because they wheeze and respond well to asthma medications. Over time, though, some develop the fixed airway obstruction characteristic of COPD.
When Asthma and COPD Overlap
Some people genuinely have features of both diseases at the same time. This is known as asthma-COPD overlap, or ACO. A systematic review published in Respiratory Research found that about 26.5% of people with asthma and roughly 29.6% of people with COPD meet criteria for this overlap. In the general population, the prevalence sits around 2%.
To be diagnosed with ACO, a person generally needs to be at least 40 years old, have fixed airflow obstruction on spirometry, have a significant smoking history (10 or more pack-years), and either a history of asthma before age 40 or a very large improvement in airflow after using a bronchodilator. At least one additional marker is also required, such as a history of allergies, elevated eosinophil counts in the blood, or repeated evidence of partial airway reversibility across multiple clinic visits.
ACO tends to be harder to manage than either condition alone. Exacerbation rates are four to five times higher in people with ACO compared to those with asthma or COPD by itself. Emergency department visits and hospitalizations are also more common, and lung function declines more rapidly.
Can Asthma Turn Into COPD?
Asthma doesn’t automatically become COPD, but long-standing, poorly controlled asthma can lead to permanent changes in the airway walls. Chronic inflammation causes the tissue lining the airways to thicken, the smooth muscle surrounding them to enlarge, and scar tissue to form around the small airways. Over years, these remodeled airways become less flexible and less able to open fully, creating a pattern of fixed obstruction that looks very similar to COPD on a breathing test.
Smoking accelerates this process significantly. About 30% of people with asthma smoke, and a proportion of these smokers develop chronic airflow limitation that becomes essentially indistinguishable from COPD. This is one of the main reasons the two conditions get conflated, especially in older adults who have had asthma for decades and also have a smoking history.
How Treatment Differs
The treatment difference matters, which is a practical reason why the distinction between asthma and COPD isn’t just academic. Inhaled corticosteroids are the backbone of asthma treatment. They reduce the eosinophilic inflammation driving the disease, and using them consistently is what keeps asthma under control for most people.
In COPD, the picture is different. Current international guidelines recommend combinations of long-acting bronchodilators as the starting treatment for most people with COPD. Inhaled corticosteroids play a more limited role and are typically added only when a person has frequent flare-ups, particularly if their blood eosinophil count is elevated, suggesting an asthma-like component to their disease.
For people with asthma-COPD overlap, treatment usually incorporates elements of both approaches. Inhaled corticosteroids are considered essential in ACO because withholding them risks undertreating the asthma component, but bronchodilators targeting the fixed obstruction are also needed. Getting the diagnosis right determines which medications you’ll use daily and which ones could be ineffective or even counterproductive.
The Key Takeaway
Asthma and COPD share the feature of obstructed airflow, which is why they’re sometimes confused. But asthma is characterized by reversible narrowing driven by allergic-type inflammation, while COPD involves permanent structural damage to the airways and lung tissue. They differ in when they start, what causes them, how they feel day to day, and how they’re treated. Some people have both, and that overlap creates a distinct clinical situation with its own diagnostic criteria and management challenges.