Table 1

Prevalence (%) of asthma, wheeze, environmental tobacco smoke (ETS) exposure at age 7–8 and 16–17 years, and personal smoking habits at age 16–17 years

	Age 7–8 years			Age 16–17 years			Difference by age p value
	Boys (n=1416)	Girls (n=1389)	Difference by gender p value	Boys (n=1416)	Girls (n=1389)	Difference by gender p value	Difference by age p value
Outcome variables
Physician-diagnosed asthma	7.5	4.2	0.001	13.6	13.0	0.680	<0.001
Current asthma	6.9	4.0	0.001	8.9	10.9	0.080	0.012
Ever wheeze	24.8	17.5	0.001	21.9	26.1	0.010	<0.001
Current wheeze	11.4	8.3	0.007	16.5	24.8	0.001	<0.001

Exposure to tobacco smoke
In utero exposure	23.1	24.3	0.439	–	–
Current maternal ETS	27.5	30.2	0.264	21.6	25.4	0.018	<0.001
Current paternal ETS	20.1	22.7	0.110	18.4	19.1	0.619	0.016
Continuous ETS mother	–	–		12.8	15.6	0.031
Continuous ETS father	–	–		6.4	7.0	0.505

Smoking habits
Occasional smokers	–	–		8.8	9.6	0.493
Daily smokers	–	–		5.7	11.4	<0.001