eTable 1. Sample characteristics of the German Health Interview and Examination Survey for Children and Adolescents (KiGGS) for the subset of adolescents aged between 11 and 17 years.

		KiGGS baseline study (2003–2006) (n=6812)			KiGGS Wave 1 (2009–2012) (n=5258)
Variable	Categories	Sample size (n)	Unweighted sample (%)	Weighted sample* (%)	Sample size (n)	Unweighted sample (%)	Weighted sample* (%)
Age	11 years	1058	15.5	13.9	715	13.6	13.9
	12 years	1008	14.8	14.2	783	14.9	14.2
	13 years	1010	14.8	14.6	769	14.6	14.6
	14 years	1003	14.7	14.4	783	14.9	14.4
	15 years	969	14.2	14.0	726	13.8	14.0
	16 years	905	13.3	14.2	738	14.0	14.2
	17 years	859	12.6	14.8	744	14.1	14.8
Sex	Boys	3492	51.3	51.3	2683	51.0	51.3
	Girls	3320	48.7	48.7	2575	49.0	48.7
Social status	Low	1010	14.8	19.1	649	12.3	23.0
	Middle	4031	59.2	62.1	3318	63.1	59.7
	High	1561	22.9	18.8	1224	23.3	17.2
	Missing values	210	3.1	–	67	1.3	–
Smoking	Daily	826	12.1	13.3	234	4.5	5.4
	Several times a week	141	2.1	2.2	71	1.4	1.3
	Once a week	49	0.7	0.7	42	0.8	0.7
	Less than once a week	274	4.0	4.2	226	4.3	4.6
	Never	5409	79.4	79.6	4371	83.1	88.0
	Missing values	113	1.7	–	314	6.0	–
Passive smoke exposure	Daily	1000	14.7	21.9	335	6.4	10.2
	Several times a week	670	9.8	13.3	347	6.6	8.6
	Once a week	546	8.0	10.3	479	9.1	10.8
	Less than once a week	2091	30.7	37.8	1693	32.2	37.4
	Never	991	14.5	16.8	1513	28.8	32.9
	Missing values	228	3.3	–	319	6.1	–
	Excluded (active smoker)	1286	18.9	–	572	10.9	–

^*Weighted figures without missing values (population figures based on official statistics as of December 31, 2010; and education distribution of head of household in the 2009 German microcensus)