Table 3.

Descriptive characteristics of the subjects and the prevalence of respiratory symptoms based on the questionnaire

Residential area	Apartment				Ger dwelling				Total
District	A urban		B urban		C urban		D suburban
	n	%	n	%	n	%	n	%	n	%
Response rate	238	79	273	91	300	100	298	99	1109	92.4
Sex
Female	129	54	123	45	122	41	141	47	594	53.6
Male	109	46	150	55	178	59	157	53	515	46.4
Age
6–8 years	135	57	161	59	146	49	176	59	618	55.7
9–12 years	103	43	112	41	154	51	122	41	491	44.3
Feeding in infancy (bottle milk)	52	22	47	17	57	19	48	16	204	18.4
History of respiratory diseases before 2 years old	68	29	89	33	65	22	66	22	288	26.0
History of diagnosed asthma	12	5.0	2	0.7	6	2.0	7	2.3	27	2.4
History of allergic diseases	52	22	57	21	38	12	29	10	176	15.9
History of pneumonia	16	7	25	9	16	5	12	4	69	6.2
Parental smoking habit at home	87	37	103	38	146	49	142	48	478	43.1
History of residence years	150	63	170	62	187	62	220	74	727	65.6
Heating type (coal using)	6	3	11	4	141	47	214	72	372	33.5
Distance from major road < 100 m	119	50	126	46	99	33	69	23	413	37.4
Daily traffic volume	16,842		16,985		19,473		7187		60,487
Respiratory symptoms
Persistent cough	60	25	50	18	95	32	111	37	316	28.5
Persistent phlegm	50	21	50	18	63	21	61	21	224	20.2
Asthma-like symptom	4	2	0	0	2	1	2	1	8	0.7
Current wheezing	22	9	14	5	17	6	11	4	64	5.8