Environmental characteristics of the entire population, the control group and the AR group.

All the values are expressed in absolute numbers and percentage in brackets *Chi-square test when conditions were respected or Fisher's exact test otherwise. Boldface values indicate statistical significance. Maternal breast-feeding beyond 3 months, Passive smoking (defined by smokers at home smoking more than 5 cigarettes a day). Overcrowding (less than 9 m2 for each person living at home). Mold exposure (visible mold and moldy smell) and cockroaches (visible cockroaches at home).