To understand COPD, it helps to have a basic picture of how healthy lungs work. When you breathe in, air travels through the airways, which branch out like a tree into smaller and smaller passages, eventually reaching clusters of tiny balloon-like air sacs called alveoli. Oxygen passes through the thin walls of these sacs into the blood, and carbon dioxide passes back out to be exhaled. The airways need to be open and elastic to allow air to move freely in both directions.

In COPD, two types of damage interfere with this process. In emphysema, the walls of the air sacs are gradually destroyed, reducing the surface area available for oxygen exchange and causing the lungs to lose their natural elasticity. Air becomes trapped in the lungs because they cannot spring back effectively. In chronic bronchitis, the lining of the airways becomes chronically inflamed and produces excess mucus, narrowing the passages and making it harder for air to move through.

Together, these changes mean less oxygen reaches the bloodstream, stale air lingers in the lungs instead of being fully exhaled, and breathing requires noticeably more effort. Over time, the lungs are simply less able to do their job.

COPD develops after prolonged exposure to substances that irritate and damage the lungs. In most cases, the damage accumulates over many years, which is why COPD is most commonly diagnosed in middle age and beyond.

• Tobacco smoke is the leading cause of COPD in the United States. Cigarette smoking causes direct, ongoing damage to the airways and air sacs. The longer a person smokes and the more they smoke, the greater the risk. However, not everyone who develops COPD has smoked, and not every smoker develops COPD, which points to the role of individual susceptibility.
• Secondhand smoke is also a recognized risk factor, particularly for people with long-term exposure in the home or workplace.
• Occupational exposures play a significant role for many people. Long-term exposure to dust, chemical fumes, vapors, and other airborne irritants in workplaces such as mines, construction sites, factories, and farms can contribute to COPD development.
• Indoor air pollution is a major cause globally, particularly in regions where biomass fuels like wood or charcoal are burned indoors for cooking or heating in poorly ventilated spaces.
• Genetics can influence who develops COPD and how severely. A specific genetic condition called alpha-1 antitrypsin (AAT) deficiency significantly raises the risk of developing COPD, even in people who have never smoked. People with this inherited condition lack a protein that normally helps protect the lungs from damage.
• Childhood lung development may also be a factor. Infections or other exposures during early development can affect lung growth and increase vulnerability to COPD later in life.

COPD symptoms often start gradually and can be easy to dismiss as simply getting older or being less fit than you used to be. This is one reason why many people are not diagnosed until the condition has already progressed.

The most common symptoms include:

• Shortness of breath, especially with physical activity, which is often the symptom that first prompts people to seek care
• A chronic cough that persists for weeks or months, sometimes producing mucus (phlegm) that may be clear, white, yellow, or green
• Wheezing, a whistling or squeaky sound when breathing, particularly during exertion or when airways are narrowed by mucus
• Chest tightness or a feeling of heaviness in the chest, especially with activity
• Fatigue and reduced stamina that make everyday tasks feel more draining than they once did
• Frequent respiratory infections such as colds, bronchitis, or pneumonia that take longer than usual to resolve

As COPD progresses, symptoms can become more persistent and limiting. Activities that were once routine, such as walking up stairs, carrying groceries, or getting dressed, may begin to require significant effort. In more advanced stages, symptoms can be present even at rest.

A COPD flare-up, also called an exacerbation, is a period when symptoms become noticeably worse than usual. Flare-ups often develop over the course of a day or two and can be frightening and disorienting. They are a significant part of living with COPD and deserve special attention.

During a flare-up, a person with COPD may experience a sharp increase in shortness of breath, a change in the color or amount of mucus, increased coughing or wheezing, or a feeling of unusual tightness in the chest. In severe cases, a flare-up can require urgent or emergency care.

Common triggers for COPD flare-ups include:

• Respiratory infections, particularly viral infections like colds and flu, which are the most frequent trigger
• Air quality issues, including smoke, smog, high pollen counts, or strong chemical odors
• Cold or dry air, which can irritate already sensitive airways
• Physical overexertion beyond what the lungs can comfortably support
• Exposure to dust or fumes in the home or environment

Recognizing your personal triggers and having a clear plan in place with your healthcare provider for how to respond when symptoms worsen are two of the most important aspects of managing COPD over the long term.

Diagnosis typically begins with a conversation about your symptoms, your history of exposure to tobacco or other irritants, and your family history. A physical examination of the lungs, including listening to your breathing patterns, is also part of the initial assessment.

The primary test used to diagnose COPD is called spirometry, a simple and painless breathing test. During spirometry, you breathe into a device that measures how much air you can exhale and how quickly you can do it. These measurements help a provider determine whether airflow is limited and, if so, how significantly. Spirometry can detect COPD even before symptoms become severe, which is one reason it is recommended for anyone with risk factors or relevant symptoms.

Additional tests may be ordered to get a fuller picture of lung health and to rule out other conditions. These can include chest X-rays or CT scans, blood tests to measure oxygen levels, and a test specifically for alpha-1 antitrypsin deficiency if that is suspected. The combination of your history, examination findings, and test results guides the diagnosis and helps your provider understand the extent of the condition.

COPD can affect anyone, but certain groups face a higher risk based on their history and characteristics.

• Current and former smokers face the greatest risk in the United States. The longer the smoking history and the more heavily a person has smoked, the higher the risk.
• People with significant occupational exposure to dust, chemicals, or fumes over many years are at elevated risk, even without a smoking history.
• Adults over 40 are more commonly diagnosed, as COPD typically develops over decades of cumulative lung damage.
• Women have seen rising rates of COPD diagnosis, in part because of changes in smoking patterns over the decades and possibly because of differences in lung anatomy that may make women more vulnerable to certain exposures.
• People with a family history of COPD or known alpha-1 antitrypsin deficiency face inherited risk independent of exposure history.
• People who experienced frequent or severe respiratory infections in childhood may have underlying differences in lung development that increase susceptibility.

It is worth noting that having one or more risk factors does not mean COPD is inevitable, and many people are surprised to learn they have it even without what they consider a significant smoking history.

While COPD cannot be reversed, daily habits can have a meaningful impact on how symptoms feel and how quickly the condition progresses.

• Avoiding smoke and irritants is the single most impactful step for anyone with COPD who currently smokes. Stopping smoking slows the rate of lung function decline more significantly than any other change. Avoiding secondhand smoke, strong chemical odors, wood smoke, and other airway irritants is also important.
• Staying physically active within your current capacity supports the muscles involved in breathing and helps maintain overall stamina. Even gentle, regular movement makes a difference. Your provider can help you understand what level of activity is safe and beneficial for your stage of COPD.
• Protecting yourself from respiratory infections is essential, since infections are the leading trigger for flare-ups. Practicing good hand hygiene and staying current on recommended vaccines can meaningfully reduce your risk.
• Eating well and staying hydrated supports overall health and helps keep mucus from becoming thick and difficult to clear.
• Monitoring your symptoms and knowing your personal baseline helps you and your provider catch changes early. Keeping a simple log of your breathing, energy, and mucus can help identify patterns and triggers.
• Managing indoor air quality by increasing ventilation, avoiding air fresheners or strong cleaning products, and using a fan or air purifier can reduce daily exposure to airway irritants at home.

If you have a history of smoking, occupational exposures, or other risk factors and are experiencing persistent shortness of breath, a chronic cough, or regular respiratory infections, speaking with a healthcare provider about COPD evaluation is a meaningful next step. Early diagnosis allows for earlier management and better long-term outcomes.

You should seek care promptly if you notice a significant worsening of your usual symptoms, particularly shortness of breath that is worse than typical, a change in the color or amount of mucus, a fever, or a feeling that you cannot catch your breath even at rest. These signs may indicate a flare-up or another lung issue that requires prompt attention.

If you have already been diagnosed with COPD and your symptoms are changing, becoming more frequent, or feeling less manageable, following up with your provider is important. COPD is a condition that benefits from ongoing, proactive care and regular reassessment over time.