COPD is a group of lung diseases that most often affects people with a history of smoking. But people who have never smoked can also get COPD.

Smoking is a major risk factor for chronic obstructive pulmonary disorder (COPD). But not all smokers get COPD, and not everyone who has COPD smokes. Even people who have never smoked can get COPD.

COPD is a general term used for conditions marked by permanent inflammation of the bronchi, the tubes that bring air into the lungs. COPD also includes damage to the air sacks of the lungs. This can make it hard to breathe.

COPD affects an estimated 65 million people worldwide. One estimate from the U.S. Centers for Disease Control and Prevention puts the number of people in the United States with COPD at 15.7 million. The actual number is probably much higher, as researchers believe that many more people are not aware that they have the condition.

Also, studies suggest the disease is much more common among non-smokers than previously believed. Between 10 and 20 percent of people with COPD have never smoked. A recent large study of Canadian residents found that non-smokers make up almost 30 percent of those with COPD.

Learn more: COPD’s effects on the lungs in pictures »

Both people who currently do not smoke (non-smokers) and people who have never smoked (never-smokers) can get COPD. Other risk factors besides smoking help predict COPD in never-smokers.

Four major risk factors for COPD are:

  1. Exposure to secondhand smoke: Being exposed to secondhand smoke as an adult can lead to COPD.
  2. Exposure to air pollution: You can develop COPD if you are exposed long-term to air pollution. You can also develop COPD from inhaling dust or the fumes of fuel burned for cooking or heating purposes. COPD can also be caused by chemicals or fumes found in the workplace.
  3. Genetics: COPD has a strong genetic component. As many as 5 percent of people with COPD have a genetic condition known as alpha-1 antitrypsin deficiency. People with this condition have too little alpha-1 antitrypsin, a protein helps protect the lungs from damage. Having too little of it can cause your lungs to deteriorate, leading to COPD. This condition also affects the liver.
  4. Age: Most people who have COPD are over 40 years old.

Additional factors include stressors to young, developing lungs. These factors include maternal smoking during pregnancy, low birth weight, tobacco exposure in childhood, and childhood respiratory infections. These conditions might also help identify people at risk for COPD.

Having asthma may also play a role in developing COPD. One study found that the presence of asthma helped predict COPD in non-smokers.

Common symptoms of COPD include:

  • needing to clear your throat often due to excessive mucus
  • being short of breath, even after mild exercise
  • wheezing, or noisy breathing
  • chest tightness
  • chronic cough
  • having low energy
  • recurrent respiratory infections

The symptoms of COPD are the same in both smokers and non-smokers. But research has shown that never-smokers with COPD may have milder symptoms than both current and former smokers. A Danish study looked at the results of 6,623 people with COPD. Of these people, 1,476 had never smoked, 2,696 were former smokers, and 2,451 were current smokers. People who had never smoked experienced fewer symptoms, a milder form of the disease, and less inflammation than current or former smokers.

COPD is often first diagnosed when people raise concerns with their doctor because shortness of breath has become a problem. However, the symptoms of COPD usually don’t appear until there is already significant lung damage. Because the disease can be less severe in non-smokers, this can lead to them being diagnosed with COPD at a later age.

Non-smokers also have fewer comorbidities, or other conditions that occur at the same time as COPD. But non-smokers can still experience flare-ups of their COPD symptoms, known as exacerbations.

There is no single test to diagnose COPD. Doctors rely on your medical history, physical examination, lung function tests, and chest imaging tests like an X-ray or CT scan.

A key tool used for diagnosing COPD is the lung function test known as spirometry, a test that measures airflow out of your lungs. However, some doctors may rely instead on the presence of smoking and physical symptoms. That has led to a concern that the disease might be overdiagnosed in smokers and underdiagnosed in non-smokers.

To help primary care doctors identify who should be tested for COPD with spirometry, researchers have been working on a simple, five-question test. It’s called CAPTURE: COPD Assessment in Primary Care To Identify Undiagnosed Respiratory Disease and Exacerbation Risk.

“It actually does not include a question about smoking,” says Dr. MeiLan King Han, an associate professor of medicine at the University of Michigan. She says that according to their research, factors other than smoking were more likely to predict who was likely to be diagnosed with COPD. Dr. Han is one of the researchers who helped develop the questionnaire, which appears below.

Learn more: How to manage COPD »

Tips for preventing for COPD usually revolve around telling smokers to quit. If you don’t smoke, don’t start. Another way to reduce your risk of developing COPD is by avoiding secondhand smoke, air pollution, and other fumes or chemicals.

There’s no cure for COPD, but you can prevent the condition from becoming worse. Getting a diagnosis early on and following your treatment plan are the most important steps to slowing the progression of your COPD.