Lower
respiratory symptoms included dry cough, phlegm (cough
with expectoration), wheezing and dyspnea. The variable
‘asthma’ was defined as the recording of wheezing and/or
dyspnea. Chronic bronchitis was defined as persistent cough
and phlegm for more than 3 months per year, lasting for
more than 2 years. Contraindications for skin prick test
were evaluated for each subject during completion of the
questionnaire and physical examination.