Table 3.

Prevalence rates (%) of potential risk factors for asthma onset among different birth cohorts

	Birth cohort				P *
	1978-1969	1968-1964	1963-1959	1958-1948
Active smoking	20.12	23.32	28.31	30.71	0.15
Passive smoking	51.89	43.18	39.58	35.93	<0.001
Paternal asthma	1.94	2.34	2.79	2.53	0.23
Paternal allergic rhinitis	6.79	5.75	5.72	4.59	0.22
Paternal atopic eczema	1.39	1.01	1.14	0.95	0.22
Maternal asthma	1.98	2.07	2.19	2.53	0.81
Maternal allergic rhinitis	5.84	5.65	5.18	3.61	0.08
Maternal atopic eczema	1.07	0.88	0.78	0.51	0.81

^*Cochran-Armitage trend test.