Chronic obstructive pulmonary disease (COPD) is a long-term lung condition that makes breathing difficult and affects millions of people worldwide. Understanding this disease can help those affected manage their symptoms and maintain a better quality of life.

What Is Chronic Obstructive Pulmonary Disease?

Chronic obstructive pulmonary disease, commonly known as COPD, is a term used to describe a group of progressive lung diseases that block airflow and make breathing increasingly difficult over time. The damage to the lungs and airways causes inflammation, which is swelling and irritation inside the airways, limiting how much air can flow in and out of the lungs. This restricted airflow is what doctors call obstruction.^[1]

When someone has COPD, their lungs undergo several harmful changes. The airways and tiny air sacs called alveoli lose their natural stretchiness or elasticity, making it harder for the lungs to work properly. The walls between many air sacs get destroyed, creating larger spaces that trap air inside. The airways themselves become thick, swollen, and narrowed, while producing too much mucus that can clog the breathing passages.^[2]

The two main types of COPD are emphysema and chronic bronchitis. Emphysema occurs when the air sacs at the end of the airways become damaged and enlarged, making it especially hard to breathe out. Chronic bronchitis happens when the lining of the airways stays constantly irritated and inflamed, producing thick mucus and causing a persistent cough. Most people with COPD have features of both conditions in varying degrees.^[1]

How Common Is COPD?

COPD represents a major global health challenge. According to the World Health Organization, COPD is the fourth leading cause of death worldwide, causing approximately 3.5 million deaths in 2021, which accounts for about 5% of all deaths globally. Nearly 90% of COPD deaths in people under 70 years of age happen in low- and middle-income countries.^[3]

In the United States, more than 14 million adults are diagnosed with COPD, and many more likely have the condition without knowing it. The disease affects more than half of those diagnosed are women, contrary to what many people might expect. Rates are higher than average among American Indian and Alaska Native populations.^[4]

In New York State alone, over 900,000 adults have been diagnosed with COPD. As many as one in four Americans with COPD have never smoked, showing that the disease can affect anyone, not just smokers.^[6]

COPD predominantly affects middle-aged and older adults, with most people being at least 40 years old when symptoms first appear. The disease is more common among women, adults 65 and older, and people with less than a high school education. Current or former smokers face the highest risk of developing COPD.^[8]

What Causes COPD?

The primary cause of COPD is long-term exposure to irritating substances that damage the lungs and airways. In high-income countries, tobacco smoking accounts for over 70% of COPD cases. In the United States, cigarette smoke remains the most common cause, though pipe, cigar, and other types of tobacco smoke can also lead to COPD, especially when the smoke is inhaled.^[3]

In low- and middle-income countries, the picture looks somewhat different. Tobacco smoking accounts for only 30-40% of COPD cases in these regions, with household air pollution serving as a major additional risk factor. This includes smoke from cooking fires and heating sources that burn wood, coal, or other biomass fuels in poorly ventilated spaces.^[3]

Beyond smoking, several other factors can cause COPD. Long-term exposure to secondhand smoke significantly increases risk. Air pollution, whether outdoors or indoors, can damage the lungs over many years. People who work with chemical fumes, industrial dusts, or toxic substances face elevated risk from workplace exposures.^[2]

A rare genetic disorder called alpha-1 antitrypsin deficiency can also lead to COPD. People with this inherited condition lack a protective protein that normally shields the lungs from damage. This genetic form of COPD can affect even non-smokers and may appear at younger ages than typical COPD.^[4]

Respiratory infections during childhood may play a role in developing COPD later in life. The damage accumulates slowly, which is why COPD typically develops over years or decades of exposure to these harmful substances.^[6]

Who Is at Risk for COPD?

Smoking stands as the single biggest risk factor for developing COPD. Anyone who smokes or used to smoke cigarettes faces a considerably higher risk than people who have never smoked. The likelihood of developing COPD increases with how much someone smokes and how long they have been smoking. However, not everyone who smokes will develop COPD, suggesting that other factors also play a role.^[2]

Women appear to face higher risk than men for developing COPD, even when smoking patterns are similar. Age matters significantly—people over 65 are more likely to have COPD than younger adults. This reflects both the cumulative nature of lung damage and the fact that older generations had higher smoking rates.^[2]

People exposed to secondhand smoke, even if they never smoked themselves, carry increased risk. Those who work in jobs where they regularly breathe chemical fumes, dusts, or toxic substances face elevated risk from these workplace exposures. Certain industries like mining, construction, and manufacturing can be particularly hazardous to lung health.^[8]

Having asthma increases the chances of developing COPD, though most people with asthma will not get COPD. A family history of COPD suggests genetic factors may make some people more vulnerable to lung damage. People with alpha-1 antitrypsin deficiency have substantially higher risk due to this inherited protective protein deficiency.^[7]

Socioeconomic factors also correlate with COPD risk. People who are unemployed, unable to work, or have less than a high school education show higher rates of the disease. Those experiencing childhood respiratory infections may have increased vulnerability to COPD in adulthood.^[8]

Symptoms and How They Affect Daily Life

COPD symptoms often appear gradually and worsen over time. One of the most challenging aspects of COPD is that symptoms typically don’t appear until significant lung damage has already occurred. By the time someone notices breathing problems, the disease may already be at an intermediate or advanced stage.^[1]

The most common symptom of COPD is shortness of breath, particularly when doing physical activities. At first, people might notice they feel winded when climbing stairs or walking uphill. As the disease progresses, even simple activities like getting dressed, cooking a meal, or walking across a room can leave someone struggling to catch their breath.^[2]

A persistent cough is another hallmark symptom of COPD. Many people develop what’s often called a “smoker’s cough”—a chronic cough that produces mucus or phlegm. This cough typically persists for three months or longer at a time for at least two years. The mucus may be clear, white, yellow, or greenish in color.^[5]

People with COPD often experience wheezing, which is a whistling or squeaky sound when breathing. They may feel tightness in their chest, as if a band is squeezing around it. Taking a deep breath becomes difficult, making it hard to fill the lungs completely. Many people with COPD develop a barrel-shaped chest as the lungs become overinflated with trapped air.^[2]

As COPD progresses, people may experience extreme tiredness and fatigue. They might lose weight unintentionally because eating becomes difficult when struggling to breathe. The skin, especially lips and fingernails, may take on a bluish tint called cyanosis when oxygen levels drop too low. Frequent respiratory infections like colds, flu, or pneumonia become more common.^[3]

The impact on daily activities can be profound. People with COPD often find it increasingly difficult to carry out normal routines. Working becomes challenging or impossible. Walking, climbing stairs, and doing household chores require extra effort and frequent rest breaks. Social activities may be limited, and many people with COPD experience depression and anxiety related to their breathing difficulties.^[8]

COPD symptoms can suddenly worsen in what doctors call exacerbations or flare-ups. During these episodes, breathing becomes much more difficult, cough and mucus production increase, and the mucus may become thicker or change color. Exacerbations usually last for several days and often require additional medication or even hospitalization.^[3]

Can COPD Be Prevented?

COPD is largely a preventable disease, and there are several important steps people can take to reduce their risk of developing it or to prevent it from worsening once diagnosed.

The single most important prevention measure is to never start smoking or to quit smoking immediately if you currently smoke. Since smoking is the main cause of COPD in the United States, avoiding tobacco is the most powerful way to protect your lungs. People who already have COPD and continue smoking will experience faster disease progression and more severe symptoms.^[5]

If you smoke and want to quit, many resources can help. Healthcare providers can recommend medications that double or triple the chances of successfully quitting for good. Support programs, both in-person and online, provide encouragement and practical strategies. In the United States, state quitlines offer free telephone counseling and resources to help people stop smoking.^[6]

Avoiding secondhand smoke is also crucial. Even if you don’t smoke yourself, regularly breathing in someone else’s smoke damages your lungs over time. Try to stay away from places where people are smoking, and if you live with a smoker, encourage them to smoke outside and away from others.^[8]

Limiting exposure to air pollution and lung irritants helps protect respiratory health. On days when air quality is poor, try to stay indoors with windows closed. If you work in an environment with dust, fumes, or chemicals, use proper protective equipment like masks or respirators, ensure good ventilation, and follow all workplace safety guidelines.^[6]

At home, avoid strong-smelling cleaning products, air fresheners, and perfumes when possible. Keep your living space well-ventilated when using any products that produce fumes. If you have COPD, these irritants can trigger symptoms even in small amounts.^[5]

Getting vaccinated against respiratory infections represents another important preventive measure. People with COPD should receive the annual flu vaccine, the pneumococcal pneumonia vaccine series, and stay up to date with COVID-19 vaccinations. These infections can be particularly dangerous for people with lung disease and can trigger severe exacerbations.^[8]

Improving indoor air quality makes a real difference, especially in regions where household air pollution contributes to COPD. Using cleaner cooking and heating methods, improving ventilation, and reducing indoor smoke exposure can help prevent COPD development in vulnerable populations.^[3]

How COPD Changes the Body

Understanding what happens inside the body with COPD helps explain why breathing becomes so difficult. The disease causes several specific changes to the lungs and airways that interfere with normal breathing mechanics.

In healthy lungs, airways and air sacs are elastic and stretchy. When you breathe in, air travels through the airways into millions of tiny air sacs called alveoli, which fill up like small balloons. The alveoli transfer oxygen from the air into the bloodstream and remove carbon dioxide from the blood. When you breathe out, the elastic air sacs deflate, pushing the old air out.^[4]

COPD disrupts this process in multiple ways. The airways and alveoli lose their natural elasticity, becoming stiff and less stretchy. This makes it harder for the lungs to expand and contract properly. Breathing out becomes especially difficult because the airways tend to collapse, trapping air inside the lungs. This trapped air takes up space, leaving less room for fresh air to come in with the next breath.^[2]

The walls between neighboring alveoli break down and get destroyed. This creates fewer but larger air sacs instead of many small ones. While this might seem like it wouldn’t matter, it actually reduces the total surface area available for oxygen and carbon dioxide exchange. Less surface area means less efficient gas exchange, so the blood doesn’t get enough oxygen and can’t get rid of carbon dioxide as effectively.^[2]

Chronic inflammation plays a central role in COPD. The airways become swollen, thick, and scarred through a process called fibrosis. This inflammation narrows the airways, making it harder for air to flow through them. The airway walls produce excessive amounts of thick, sticky mucus that can further clog the breathing passages.^[2]

In chronic bronchitis, the mucus-producing glands in the airways become enlarged and overactive. The constant irritation and inflammation of the airway lining triggers ongoing mucus production. This excess mucus must be coughed up regularly, leading to the characteristic chronic cough of COPD.^[1]

These changes don’t happen overnight. COPD develops gradually over years or decades as repeated exposure to irritants causes cumulative damage. The lungs have remarkable capacity to heal minor injuries, but constant assault from cigarette smoke or other irritants overwhelms the repair mechanisms. Eventually, the damage becomes permanent and irreversible.^[1]

As COPD progresses, the body tries to compensate for poor oxygen delivery. The heart may work harder to pump blood, potentially leading to pulmonary hypertension, which is high blood pressure in the arteries going to the lungs. This can eventually cause right-sided heart failure, a condition called cor pulmonale. The body might make extra red blood cells to carry more oxygen, a condition called polycythemia.^[2]

Low oxygen levels in the blood, called hypoxemia, and high carbon dioxide levels, called hypercapnia, can develop as the disease becomes more severe. These abnormal blood gas levels can affect other organs and lead to serious complications. The lungs’ weakened state also makes infections more likely and harder to fight off, increasing the risk of pneumonia and other respiratory infections.^[2]