Table 1.

Demographic Characteristics of Participants in the Wuhan Smoking Prevention Trial (1998–1999) and the Children's Health Study (1993–2009), China and California

Study and Characteristic	Gender						Total
	Male			Female
	No.	%	Mean (SD)	No.	%	Mean (SD)	No.	%	Mean (SD)
Wuhan Smoking Prevention Trial
Smoking initiation
Yes	498	40.9		208	18.6		706	30.2
No	720	59.1		913	81.5		1,633	69.8
Total	1,218	100.0		1,121	100.0		2,339	100.0
Agea, years
Yes			12.65 (0.67)			12.52 (0.61)			12.62 (0.66)
No			12.49 (0.66)			12.44 (0.70)			12.46 (0.68)
Total			12.55 (0.67)			12.45 (0.68)			12.51 (0.68)
Children's Health Study
Smoking initiation
Yes	59	20.7		70	22.0		129	21.4
No	226	79.6		248	78.0		474	78.6
Total	285	100.0		318	100.0		603	100.0
Age at initiationb, years			15.12 (2.20)			14.99 (1.99)			15.05 (2.09)

Abbreviation: SD, standard deviation.

^aAge at interview.

^bAge at which the participant first reported smoking in the past year.