Table 1

Characteristics of study population and prevalence of risk factors in three consecutive surveys

Characteristic/risk factor1992–19931995–19971999–2000p‐value for trend
Study participation1324 (74.9)1668 (80.6)1250 (73.9)0.2761
Male sex630 (47.6)837 (50.2)609 (48.7)0.6211
Swiss nationality1029 (77.7)1250 (75.4)938 (75.5)0.2654
Urban residency851 (64.3)1070 (64.2)824 (65.9)0.3306
Low parental education856 (67.2)993 (61.8)701 (58.9)<0.0001
Parental farming105 (7.9)93 (5.6)81 (6.5)0.2892
Mother's history of asthma58 (4.4)88 (5.3)73 (5.8)0.1113
Father's history of asthma79 (6.0)86 (5.2)77 (6.2)0.6596
Mother's history of hay fever144 (10.9)181 (10.8)180 (14.4)0.0024
Father's history of hay fever130 (9.8)192 (11.5)152 (12.2)0.0809
Breastfeeding951 (73.37)1332 (80.9)1001 (84.2)<0.0001
No siblings165 (12.7)206 (12.4)131 (10.6)0.0768
ETS exposure by mother308 (23.3)399 (24.4)303 (25.9)0.1316
Student current smoker92 (7.0)218 (13.1)182 (14.6)<0.0001
Single oven heating with wood/coal132 (10.0)244 (14.7)175 (14)0.0123
Water spots or mildew313 (23.6)362 (21.7)287 (23.00)0.8607
Carpets in student's bedroom1038 (79.2)1201 (72.7)764 (61.9)<0.0001
Any pets833 (62.9)1006 (60.3)725 (58.0)0.0132
Pets in student's bedroom447 (36.5)548 (34.5)403 (33.6)0.1621
Removed carpets due to allergy39 (3.0)65 (4.0)73 (5.9)0.0002
Removed pets due to allergy34 (2.6)28 (1.7)31 (2.5)0.845
Mother filled in questionnaire1108 (84)1409 (84.9)1034 (83.2)0.4408
Parents perceive air pollution as a risk factor for respiratory disease in child166 (13.3)188 (11.9)136 (11.6)0.2316
  • Data are presented as n (%) unless otherwise stated

  • ETS: environmental tobacco smoke