MJA Vol 177 16 September 2002 S61 PATHOPHYSIOLOGY AND DIAGNOSIS Supplement The Medical Journal of Australia ISSN: 0025-729X 16 Septem- ber 2002 177 6 S61-S63 ©The Medical Journal of Australia 2002 www.mja.com.au Pathophysiology and diagnosis EXERCISE-INDUCED ASTHMA (EIA) is the term used to describe the transient reduction in lung function that occurs after vigorous exercise. 1 A reduction in FEV 1 of 13.2% or more after exercise is diagnostic of EIA. 2 A prevalence of EIA of between 19.3% and 23.4% has been reported in Australian schoolchildren. 3,4 While severity of EIA was found to be associated with the number of wheeze attacks per year, 40% of children identified with EIA had not been diagnosed with asthma by a doctor. 3 Exercise is the most common stimulus for inducing an attack in asthmatic children. Recognition of EIA is impor- tant, because full participation in sporting activities is a goal in the management of childhood asthma. Failure to recognise EIA EIA is not predicted by risk factors, including positive answers to items about asthma in questionnaires, 5 nor is it excluded by failure to report symptoms. In a child with undiagnosed EIA, the enquiry that has the most potential to elicit a positive response and thus identify EIA is “Do you feel more breathless/wheezy/symptomatic five to ten minutes after you stop exercise than during exercise.” There are many reasons why EIA is not recognised. Firstly, it occurs most commonly after exercise, so it may not limit performance unless the child has moderate to severe asthma. Secondly, children may fail to notice the symptoms of EIA until they take part in organised or competitive sport. Thirdly, 50% of children become refrac- tory to the bronchoconstricting effects of exercise when exercise is repeated within an hour or warm-up occurs before exercise. This refractoriness means that the associa- tion of exercise and “asthma” symptoms does not occur on all occasions when exercise is performed. EIA as a marker of airway inflammation: the role of steroids Most children with well-controlled asthma do not need medication before exercise. 6 Thus, taking 400 g of budeso- nide for 4 weeks reduced the severity of EIA to such an extent that less than 10% of the standard dose of terbutaline was required for complete prevention of EIA. In a recent study of 57 children with asthma and mild EIA (25% fall in forced expiratory volume in one second [FEV 1 ] after exercise) and a normal FEV 1 % predicted, low doses of budesonide for 12 weeks significantly reduced the severity of EIA (Box 1). 7 A study in children with moderate EIA (34% fall in FEV 1 after exercise) showed that treatment with 100 g or 250 g of fluticasone for three weeks was equally Exercise-induced asthma in children: a marker of airway inflammation Sandra D Anderson Department of Respiratory Medicine, Royal Prince Alfred Hospital, Camperdown, NSW. Sandra D Anderson, PhD, DSc, Principal Hospital Scientist. Correspondence: Dr Sandra D Anderson, Department of Respiratory Medicine, Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050. sandya@mail.med.usyd.edu.au ABSTRACT What we know ■ Exercise-induced asthma (EIA) occurs in up to 23% of schoolchildren. ■ In 40% of children with demonstrable EIA, no clinical diagnosis of asthma has been made. ■ Children with asthma and EIA have eosinophils in their sputum, consistent with active asthma. ■ EIA is well controlled in 50%–65% of children with moderate to severe asthma, so that only a minority will need prophylactic therapy immediately before exercise. ■  2 -Agonists are not the most suitable therapy for preventing EIA if they need to be used on a daily basis. ■ The severity of EIA appears to be an indirect index of the severity of airway inflammation. What we need to know ■ Do non-symptomatic children with EIA require treatment for asthma? ■ Does failure to identify and treat children unaware of their airways narrowing after exercise lead to airflow limitation in the long term, particularly in the small airways? ■ Can exercise, or surrogate tests used to identify EIA, also be used to assess children with asthma? ■ What is the minimum dose of steroid required to inhibit EIA, as high doses of steroids may be inappropriate in children? ■ What is the best prophylactic treatment for EIA in children whose asthma is otherwise well controlled by inhaled steroids? ■ What is the best prophylactic treatment for EIA in children with frequent episodic asthma or mild persistent asthma? ■ Are leukotriene antagonists alone better than  2 -agonists alone in preventing EIA throughout the day? ■ How many children taking long-acting  2 -agonists twice daily, either alone or in combination with an inhaled steroid, experience breakthrough EIA during school and MJA 2002; 177: S61-S63 require rescue medication?