Asthma, a disease of the airways, occurs in people of all ages, and wheeze (rough breathing) is the most common symptom. The most recent revised global estimate of asthma suggests that as many as 334 million people have asthma. The historical view of asthma being a disease of high-income countries no longer holds: most people affected are in low- and middle-income countries, and its prevalence is estimated to be increasing fastest in these countries. Asthma is the most common chronic disease among children. It is under-diagnosed and under-treated, creating a substantial burden to individuals and families and possibly restricting individuals’ activities for a lifetime.
What is asthma?
Asthma is a disease of the bronchial tubes in the lungs (the “airways”). People with asthma typically experience “wheezing”, a high-pitched whistling sound heard during breathing, especially when breathing out. However, wheezing does not always occur, and asthma can also involve breathlessness, chest tightness or coughing. The underlying process includes chronic inflammation of the airways, reversible obstruction of the flow of air in and out of the airways, and the tendency of the airways to over-react to stimuli.
Asthma most commonly develops in early childhood, and more than three-quarters of children who develop asthma symptoms before age 7 no longer have symptoms by age 16. However, asthma can develop at any stage in life, including adulthood.
Causes of asthma
The fundamental causes of asthma are not completely understood. The strongest risk factors for developing asthma are a combination of genetic predisposition with environmental exposure to inhaled substances and particles that may provoke allergic reactions or irritate the airways, such as:
- indoor allergens (for example house dust mites in bedding, carpets and stuffed furniture, pollution and pet dander)
- outdoor allergens (such as pollens and moulds)
- tobacco smoke
- chemical irritants
- air pollution
Other triggers can include cold air, extreme emotional arousal such as anger or fear, and physical exercise. Even certain medications can trigger asthma: aspirin and other non-steroid anti-inflammatory drugs, and beta-blockers (which are used to treat high blood pressure, heart conditions and migraine).
Management of asthma
Although asthma cannot be cured, appropriate management can control the disease and enable people to enjoy good quality of life.
Short-term medications are used to relieve symptoms. People with persistent symptoms must take long-term medication daily to control the underlying inflammation and prevent symptoms and exacerbation.
Medication is not the only way to control asthma. It is also important to avoid asthma triggers – stimuli that irritate and inflame the airways. With medical support, each asthma patient must learn what triggers he or she should avoid. Failure to use appropriate medications or to adhere to treatment can lead to death.
Preventive and remedial measures
- Eat a balanced diet: Prolonged exclusive breastfeeding was once thought to protect against allergic diseases, including asthma, but extensive research has shown that this is not the case. Many components of diet during later childhood and adult life have been studied in relation to asthma. The balance of evidence suggests that diets that are widely recommended to prevent cardiovascular diseases and cancer may slightly reduce the risk of asthma. A link has been established between obesity and asthma, although the mechanisms are not clear.
- Avoid exposure to causal agents: Occupational exposures provide some of the clearest examples of remediable causes of asthma. Special care is required in high-risk occupations (baking, woodworking, farming, exposure to laboratory animals, and use of certain chemicals, notably paints containing isocyanates) to minimize inhalation of potentially harmful substances, and care to reduce exposure to chemical cleaning agents in the home is also needed.
- Don’t smoke or go near second hand smoke: Smokefree environments are important for people of all ages. Little is known about the factors affecting asthma after middle age, when there is substantial overlap between the reversible airflow obstruction, which is typical of asthma, and the irreversible airflow obstruction of chronic obstructive pulmonary disease (COPD). Active smoking is a major and remediable cause of COPD, and probably contributes to some cases of adult-onset asthma. Smoking should therefore be discouraged among both asthmatics and non-asthmatics alike.