Table 1—

Patient characteristics

CaseAge at presentation yrsOccupationSmoking statusAtopy#Previous asthmaFirst exposure to first symptoms yrs
142Swimming instructorNeverYesYes10
233LifeguardNeverYesUntil age 11 yrs14
349LifeguardExsmokerNoNo12
444Industrial chemistExsmoker 10 pack-yrsNoNo3
  • #: Defined as at least one weal of ≥3 mm following skin-prick testing to common environmental allergens

  • : Previous asthma, patient or general practitioner report of chest tightness or wheeze improving with inhaled bronchodilators or steroids