COPD Causes and Risk Factors

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Cigarette smoking is the most common cause of COPD in the United States. Long-term smoking or breathing in tobacco smoke or pollutants in the air damages the lungs and airways.

In healthy lungs, the air that is breathed in travels down bronchial tubes bronchial tubes (BRONG-ke-al…):
The bronchial tubes, or bronchi, are two tubes that branch off the trachea, or windpipe. Bronchial tubes carry air to the lungs. The most common problem with the bronchi is bronchitis, an inflammation of the tubes. , which often branch many times into thousands of smaller, thinner tubes called bronchioles. These tubes end in bunches of tiny round air sacs called alveoli alveolus (al-VEE-uhl-us):
A tiny air sac at the end of the bronchioles (tiny branches of air tubes) in the lungs. The alveoli are where the lungs and the bloodstream exchange carbon dioxide and oxygen. Carbon dioxide in the blood passes into the lungs through the alveoli. Oxygen in the lungs passes through the alveoli into the blood. , which are elastic or stretchy.

In COPD, less air flows in and out of the airways for one or more reasons:

• The airways and air sacs lose their elastic quality.
• The walls between many of the air sacs are destroyed.
• The walls of the airways become thick and inflamed.
• The airways make more mucus than usual and can become clogged.

The following may raise your risk of COPD:

• Smoking: This is the main risk factor for COPD. Three out of four people who have COPD smoke or used to smoke. People who have a family history of COPD are more likely to develop the disease if they smoke.
• Other lung irritants: These may include long-term exposure to air pollution, chemical fumes and dust from the environment or workplace, smoke from home cooking and heating fuels without ventilation, and secondhand smoke, which is smoke in the air from other people smoking.

  Research for your health

  NHLBI-supported research research (REE-serch):
  The scientific study of nature that sometimes includes processes of health and disease in people. Biomedical research can be defined as basic and pre-clinical, clinical and population science, implementation, and translational. Basic research seeks to understand the mechanisms of biology, disease, or behavior. Pre-clinical research connects basic science with clinical research. Clinical and population science research includes clinical trials that find safe and effective ways to prevent, detect, or treat diseases. Implementation research involves the adoption of interventions into routine clinical care for the general population. Translational research moves scientific discovery from basic and pre-clinical research to clinical studies and finally to clinical practice. found that having smaller airways for your lung size can also raise your risk for COPD. Smaller airways can prevent your lungs from working as well as they should. Lung function declines naturally as we age, so people with smaller airways may develop symptoms like those of COPD later in life, even if they do not smoke or are not exposed to lung irritants.

  Learn more about our ongoing research on COPD.
• Changes to lung growth and development: Conditions affecting the lungs when a baby is still in the uterus or during childhood can increase the risk. Examples include smoking in pregnancy or childhood asthma. Air pollution can also limit the growth of a child’s lungs and increase their risk of developing COPD.
• Infections: Conditions such as HIV and tuberculosis can raise your risk.
• Age: Your age may play a role in COPD risk if you have other risk factors, such as smoking. Most people who have COPD are at least 40 years old when  symptoms symptom (SIMP-tum):
  A problem that a patient experiences that may indicate disease but cannot be seen and does not show up on medical tests or procedures; some examples include headache, fatigue, nausea, or pain.  begin.
• A condition that runs in families, called alpha-1 antitrypsin (AAT) deficiency: If you are born with this condition, smoking or long-term exposure to fumes or dust can lead to lung damage and COPD. AAT deficiency can also raise your risk for developing COPD at a younger age. Other potential genetic genetic (jeh-NEH-tik):
  Having to do with genes. Most genes are sequences of DNA that contain information for making specific proteins or molecules of RNA that perform important functions in a cell. The information in genes is passed from parents to children. risk factors include vitamin D deficiency, and mutations in CHRNA genes gene (jeen):
  The unit that passes heredity from parents to children. Genes are pieces of DNA and contain information for making a specific protein. . Learn more about AAT deficiency.

Fact sheet

COPD Learn More Breath Better: Are You at Risk?

Learn more about the risk factors for COPD.

View the fact sheet.

COPD affects both men and women. However, COPD may affect men and women differently.

The reason for the differences in COPD between men and women is not known. Researchers think the cause may be related to hormones hormone (HOR-mone):
Substance made in glands throughout the body. Hormones are released into the blood to travel throughout the body to control other body functions. or other physiological differences, or differences in biology. Women also have smaller lungs than men do, which may make their airways more prone to narrowing when exposed to irritants.