Asthma is a chronic disease of the small airways in the lung. Airway inflammation and associated bronchoconstriction leads to recurrent attacks of cough, wheezing, breathlessness or chest tightness. The severity and frequency of these episodes varies from occasional slight wheezing to severe or rarely life-threatening attacks.
The underlying causes of asthma are not fully understood, but attacks are probably caused by an interaction between a susceptible host and the environment. Environmental triggers may include viral upper respiratory tract infections, common allergens such as pollen, dust mites and pet dander, or more general exposures such as cold air or physical exercise. Asthma is more common in those with a family history of asthma or eczema and is also more common among children whose parents smoke. It often co-exists with hay fever.
Asthma is common in Scotland and internationally, with approximately 235 million sufferers worldwide (according to the World Health Organisation). It tends to be under-diagnosed, indicating official figures may be an underestimate. The annual mortality associated with asthma in Scotland is relatively low; however asthma reduces the quality of life of sufferers, demands regular treatment and is presently incurable.
Acknowledgements: ScotPHO would like to thank Oliver Meller-Herbert, who drafted these pages on asthma. We also thank Dr Hilary Pinnock, the University of Edinburgh's Allergy and Respiratory Research Group and Sharon Pfleger for helpful comments.