Table 1. Characteristics of subjects.

	Fourth graders (age 9–10 years)			Seventh graders (age 12–13 years)
	Boys (n = 661)	Girls (n = 636)	P-value	Boys (n = 566)	Girls (n = 522)	P-value
Age (years)	9.0 (9.2)	9.0 (9.3)	0.082	12.0 (12.3)	12.0 (12.3)	0.433
Height (cm)	134.6	133.8	0.198	154.5	152.7	0.001
Weight (kg)	30.0	29.2	0.006	42.9	43.3	0.974
BMI (kg/m2)	16.5	16.2	0.004	17.9	18.3	0.005
SBP (mm Hg)	108.0 (109.3)	107.0 (107.7)	0.009	110.0 (109.8)	105.0 (106.7)	<0.001
DBP (mm Hg)	60.0 (58.3)	58.0 (57.4)	0.026	56.0 (56.6)	56.0 (57.3)	0.323
Family history of HT (%)	3.6	4.2	0.669	5.8	6.1	0.898

Data are expressed as a median (mean) or percentage (%).

Mann–Whitney U-test or the chi-square test.

BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; HT, hypertension.