Table 4. Prevalence of respiratory symptoms in the first survey in relation to environmental factors.

	N	History of allergic diseases	Bronchitis ever	Chronic cough	Chronic phlegm	Asthma	Wheeze
Males
Maternal smoking habits
Yes	156	48.1	23.1	1.3	1.9	7.7	8.3
No	1,107	55.6	21.3	1.3	1.1	7.0	5.4
p-value		0.091	0.692	0.716	0.609	0.898	0.202
Structure of house
Steel or reinforced concrete	404	57.4	26.7	2.0	1.5	7.9	7.7
Wood	859	53.4	19.1	0.9	1.0	6.8	4.9
p-value		0.205	0.003	0.199	0.696	0.525	0.063
Type of heating appliance
Unvented	804	53.4	21.5	1.6	1.2	6.7	6.0
Vented	459	57.1	21.6	0.7	1.1	7.8	5.4
p-value		0.223	0.960	0.226	0.979	0.525	0.796
Areas
0-49 m from trunk roads	82	62.2	25.6*	0.0	0.0	8.5	8.5
≥ 50 m from trunk roads	623	57.1*	25.5**	1.3	1.3	7.9	7.1*
Rural areas	558	50.9	16.5	1.4	1.3	6.1	3.9
p-value		0.010	< 0.001 †	0.555	0.590	0.210†	0.012†
Females
Maternal smoking habits
Yes	135	51.9	22.2	3.7	3.7	8.9	7.4
No	1,108	52.0	20.7	2.1	1.5	6.8	4.8
p-value		0.951	0.758	0.370	0.145	0.464	0.269
Structure of house
Steel or reinforced concrete	451	54.5	24.6	1.8	1.3	9.3	4.9
Wood	792	50.5	18.7	2.5	2.0	5.7	5.2
p-value		0.190	0.016	0.509	0.507	0.022	0.923
Type of heating appliance
Unvented	802	53.7	21.1	1.9	1.7	7.2	5.6
Vented	441	48.8	20.4	2.9	1.8	6.6	4.1
p-value		0.104	0.839	0.305	0.891	0.751	0.298
Areas
0-49 m from trunk roads	93	53.8	28.0**	1.1	1.1	8.6	5.4
≥ 50 m from trunk roads	630	54.0	23.3**	1.9	1.7	87**	5.7
Rural areas	520	49.2	16.5	2.9	1.9	4.6	4.2
p-value		0.260	0.001 †	0.392	0.848	0.020	0.516

* p < 0.05, ** p < 0.01, compared with children living in rural areas.

^† p-value for the trend in the rates for roadside > non-roadside > rural area.