Chronic symptoms were defined17 as follows: chronic
cough, with cough in the morning or during the day or night for
3 months a year for 2 years; chronic sputum, with phlegm in
the morning or during the days for 3 months a year for 2 years;
chronic wheeze, with chest wheezing or whistling most days or
nights; and chronic dyspnea, with shortness of breath on effort on
the level or walking up a slight hill