Table 1.

Distribution of study population by gender and age.

		Ban Thi, Bac Kan (n = 195)		Tan long, Thai Nguyen (n = 208)		Total (n = 403)
		n	%	n	%	n	%
Gender	Boys	110	56.4	123	59.1	233	57.8
	Girls	85	43.6	85	40.9	170	42.2
Age group	<6	45	23.0	55	26.5	100	24.8
	6-10	113	58.0	97	46.6	210	52.1
	11-14	37	19.0	56	26.9	93	23.1
	Mean (SD)	8.61 ± 2.90		8.17 ± 2.88		8.40 ± 3.15