Asthma vs. COPD: What's the Difference?

Medically Reviewed by Carmelita Swiner, MD on December 02, 2022
6 min read

Asthma and chronic obstructive pulmonary disease (COPD) are lung diseases. Both cause swelling in your airways that makes it hard to breathe.

With asthma, the swelling is often triggered by something you’re allergic to, like pollen or mold, or by physical activity. COPD is the name given to a group of lung diseases that include emphysema and chronic bronchitis.

Emphysema happens when the tiny sacs in your lungs (called alveoli) are damaged. Chronic bronchitis is when the tubes that carry air to your lungs (bronchial tubes) get inflamed. Smoking is the most common cause of those conditions (and COPD).

Asthma gets better. Symptoms can come and go, and you may be symptom-free for a long time. With COPD, symptoms are constant and get worse over time, even with treatment.

Some people have asthma and COPD at the same time. If you have symptoms of both diseases, your doctor may call it asthma-COPD overlap (ACO).

It's possible to have symptoms of both asthma and COPD. ACO isn't a separate disease. The name is a way to acknowledge the mix of symptoms.

It's not clear what causes ACO. Having COPD for a long time may change the way your lungs work and make you more likely to get it. Or it might start if you smoke while you have asthma. It may also happen for reasons no one has figured out yet.

It's important to find and treat ACO because it can be more serious than having either condition alone. There's no cure, but you and your doctor can work together to help you breathe and live better.

People who smoke or breathe in pollution or chemicals at work for many years have higher chances of having COPD. That's why the condition often starts in middle age or later in life.

Asthma is sometimes caused by gene changes that are passed down through families. If one of your parents has the disease, you're more likely to have it.

Symptoms of asthma often start in childhood, and the condition is one of the most widespread long-term illnesses in kids. It affects about 1 in 10 children.

Besides a family history of the condition, a few things can raise your chances of asthma:

  • Allergies
  • Lung infections
  • Smoking
  • Being around chemicals or other irritants in the air

People who get ACO tend to be over 40 but younger than people with just COPD, and they have allergies (or have family members with them).

Researchers now know that childhood asthma greatly raises your chances for having COPD later on. Although many kids outgrow their asthma, some have lungs that don’t mature the way they should or work as well compared with people who’ve never had asthma.

Experts think asthma either causes COPD or is one of the factors that make COPD more likely in adulthood.

That’s especially true for kids who have “persistent childhood asthma.” Those children have trouble breathing almost every day. One study found that 11% of kids who had this kind of severe asthma had COPD as young adults.

What’s more, 3 out of 4 children with persistent asthma showed signs of lower lung capacity or growth by their early 20s. That could put them on a path to get COPD later. Boys are much more likely than girls to have problems with their lungs.

More research is needed to see if and which kind of treatment may help prevent childhood asthma from turning into COPD.

Since asthma and COPD both make your airways swell, they both can cause:

One main difference is that asthma typically causes attacks of wheezing and tightness in your chest. COPD symptoms are usually more constant and can include a cough that brings up phlegm.

If you have ACO, you may also have:

  • Flare-ups or times when symptoms get worse but usually get better with medicine that opens your airways, like a bronchodilator
  • Neutrophils or eosinophils (white blood cells linked to inflammation) in your spit

With ACO, you'll have more symptoms than with asthma or COPD alone, and you'll have more severe attacks more often. You’ll need to go to the hospital more. But someone with ACO may have a better outlook than with COPD alone.

To figure out which condition you have, your doctor will start with a physical exam and questions about your medical history. They’ll look at your nose and throat and listen to your lungs with a stethoscope. They’re likely to ask about things like:

  • Your symptoms
  • If you have a family history of asthma or allergies
  • If you smoke or are around secondhand smoke
  • If you work around chemicals or other things that can irritate your lungs

Your doctor will also want to do a test called spirometry that checks how well your lungs work. You’ll blow into a mouthpiece, and a machine will measure how much air you can blow out and how fast you can do it.

If your doctor thinks you have asthma, they might ask you to breathe in a medicine called a bronchodilator and take the spirometry test again. If you have asthma, your lungs should work better after you take the medicine.

Another way to diagnose asthma is with a challenge test. You breathe in an asthma trigger like a strong scent or the drug methacholine. Then you take a spirometry test to see if your airways have narrowed. Weaker airflow afterward can be a sign that you have asthma.

If you had severe asthma as a kid or have a child who does, doctors recommend a spirometry test every year. The test may catch signs of a lung problem or early symptoms of COPD so you can get treated.

Tests used to diagnose COPD may also include:

  • Chest X-ray. This uses radiation in low doses to make images of your lungs.
  • Arterial blood gas test. This measures how much oxygen is in your blood. COPD can make your blood oxygen level drop.

If you have a fairly even mix of traits from both asthma and COPD, you may have ACO.

With asthma, symptoms come and go in the form of attacks. For some people, these may happen more often or be more serious over time.

Asthma medicines come in two types. Quick-relief medicines relax your airways to let more air into your lungs. You take them when you have an asthma attack to quickly stop wheezing and other symptoms.

  • Short-acting beta-agonists relax the muscles around your airways.
  • Anticholinergics both relax your airways and reduce the amount of mucus in your lungs.

Long-term medicines help keep asthma symptoms at bay. You take these medicines every day.

  • Corticosteroids bring down swelling in your lungs. You breathe in the medicine through a device called an inhaler or take them as pills. Sometimes, they're combined with one or more other medications.  
  • Inhaled long-acting beta-agonists relax the muscles around your airways to help you breathe more easily. These are always used along with other asthma medications.
  • Other anti-inflammatory drugs, such as cromolyn, help keep your airways from swelling up.
  • Leukotriene modifiers are pills or liquids that block the process that causes airway swelling.
  • Immunomodulators work directly on the immune system. These are also called biologics.
  • Theophylline helps open your airways.
  • Allergy shots or sublingual tablets are two types of immunotherapy that may help if your asthma is triggered by allergies.

COPD causes daily symptoms that get worse over time. Following a treatment plan can slow this down and help your lungs work better longer. COPD is treated with some of the same medicines as asthma, while others are different.

  • Bronchodilators relax the muscles of your airways.
  • Corticosteroids ease swelling inside your airways.
  • Combination inhalers include both a corticosteroid and one or more bronchodilators to ease breathing in different ways.
  • Phosphodiesterase-4 (PDE4) inhibitors bring down swelling in your lungs to prevent COPD flare-ups.
  • Antibiotics treat infections that can make your COPD symptoms worse.

A few nondrug treatments can also help control COPD symptoms.

  • Pulmonary rehabilitation. This program teaches you exercises and suggests changes in your diet and other tips to help you live better with COPD.
  • Supplemental oxygen. If your lungs can't pull enough oxygen into your blood, you may need to breathe in oxygen from a tank or machine.
  • Surgery. Removing the damaged areas of your lungs can sometimes help the healthy parts work better.

Whether you have COPD, asthma, or both, it's important to stop smoking. It’s also best to stay away from anything that irritates your lungs, such as:

  • Spray chemicals like cleaning products and bug killers
  • Allergens like mold, dust, and pollen
  • Perfumes and other scents
  • Secondhand smoke