Distribution of selected variables among cases and controls.

*Derived from two-sided χ2 test for comparison of discrete variables and unpaired Student’s t-test for continuous variables.
†Selective variables were transformed into logarithmic model before unpaired Student’s t-test between cases and controls.
‡Some information of concomitant asthma or family history of allergic diseases was not available in cases.
IQR, interquartile range; VAS, visual analogue scales.