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Asymptomatic bronchial hyperresponsiveness to exercise in childhood and the development of asthma related symptoms in young adulthood: the Odense Schoolchild Study
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  1. Finn Rasmussena,
  2. Jess Lambrechtsena,
  3. Hans Christian Siersteda,
  4. Henrik Steen Hansenb,
  5. Niels-Christian Hansena
  1. aDepartment of Respiratory Diseases, bDepartment of Cardiology, cOdense University Hospital, Denmark
  1. Dr F Rasmussen, Kløvervænget 2 , Odense University Hospital, Denmark.

Abstract

BACKGROUND Exercise testing may be of value in identifying a group of children at high risk of subsequently developing respiratory symptoms. As few longitudinal studies have investigated this issue, the bronchial hyperresponsiveness to exercise in asymptomatic children was evaluated as a risk factor for developing asthma related symptoms in young adulthood.

METHODS A community based sample of 1369 schoolchildren, first investigated in 1985 at a mean age of 9.7 years, was followed up after a mean of 10.5 years. Nine hundred and twenty children (67%) were asymptomatic in childhood and 777 (84.9%) of these were re-investigated at follow up. At the first examination a maximum progressive exercise test on a bicycle ergometer was used to induce airway narrowing. The forced expiratory volume in one second (FEV1) after exercise was considered abnormal if the percentage fall in FEV1 was more than 5% of the highest fall in the reference subjects characterised by having no previous history of asthma or asthma related symptoms. The threshold for a positive test was 8.6% of pre-exercise FEV1.

RESULTS One hundred and three subjects (13%) had wheeze within the last year at follow up and, of these, nine (9%) had been hyperresponsive to exercise in 1985. One hundred and seventy subjects (22%) had non-infectious cough within the previous year, 11 of whom (6%) had been hyperresponsive to exercise in 1985. Multiple regression analysis showed that subjects with hyperresponsiveness to exercise had an increased risk of developing wheeze compared with subjects with a normal response to exercise when the fall in FEV1 after exercise was included as a variable (threshold odds ratio (OR) 2.3 (95% CI 1.1 to 5.5)). The trend was not significant when exercise induced bronchospasm was included as a continuous variable (OR 1.02 (95% CI 0.97 to 1.06)).

CONCLUSIONS Asymptomatic children who are hyperresponsive to exercise are at increased risk of developing new symptoms related to wheezing but the predictive value of exercise testing for individuals is low.

  • asthma
  • exercise testing
  • children
  • young adults
  • symptom development

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