Asthma

Asthma is a long-term disease of the airways, the passages that carry air into and out of the lungs. In people with asthma, airway inflammation and changes in the muscles around the airways can make them narrow at times and restrict airflow, especially when breathing out. The condition varies: symptoms and lung function can improve or worsen over days or longer periods, and severity differs among people. Asthma can begin in childhood or adulthood.

Common symptoms include wheezing, coughing, shortness of breath and a feeling of tightness in the chest. They may come and go, occur at night or with exercise, and sometimes intensify in an asthma attack, also called an exacerbation. Triggers differ from person to person; viral respiratory infections, pollen and other allergens, smoke, air pollution, cold air and exercise can provoke or worsen symptoms. A trigger is not necessarily the underlying cause of the disease, and symptoms resembling asthma can also occur in other conditions.

A diagnosis is based on a pattern of variable respiratory symptoms together with evidence that airflow out of the lungs varies. Clinicians may use spirometry, which measures how much air a person can exhale and how quickly, sometimes comparing results before and after a medicine that opens the airways. Other tests may be considered when needed. A symptom history alone can be insufficient because asthma symptoms overlap with other illnesses; objective testing can be difficult in very young children, so assessment depends on age and clinical context.

Asthma cannot currently be cured, but it can often be controlled. Inhaled medicines deliver treatment to the airways; anti-inflammatory medicines, including inhaled corticosteroids, are central to contemporary management, with care selected for the individual. Health professionals may also help patients identify relevant triggers and develop an action plan. Asthma remains an important public-health concern where people are not diagnosed or cannot obtain appropriate treatment. The World Health Organization estimated that 363 million people had asthma and that it caused 442,000 deaths worldwide in 2023; these are global estimates, not a count of every case.