Table 1.

Demographic and exposure variables in a sample of Chinese adolescents (N = 1609)

Variables	N	%
Total	1609	100
Gender
Male	588	36.5
Female	1021	63.5
Age(yr)
≤ 15	243	15.1
16	526	32.7
17	552	34.3
18	288	17.9
Grade
10	485	30.1
11	692	43.0
12	432	26.9
Only-child status
Yes	397	24.7
No	1212	75.3
Someone in the community is infected
Yes	92	5.7
No	1517	94.3
A relative or friend is infected
Yes	13	0.8
No	1596	99.2
A relative or friend died from the infection
Yes	3	0.2
No	1606	99.8
Smoker
Yes	31	19.3
No	1578	80.7
Drinker
Yes	93	5.8
No	1516	94.2