Table 2.

Characteristics of participants of Young Hearts studies, 1990 and 2000. Values are means (standard deviations) unless stated otherwise

	Participants aged 12						Participants aged 15
	Males			Females			Males			Females
Characteristics	1990	2000	P value	1990	2000	P value	1990	2000	P value	1990	2000	P value
Sample size	251	530		248	514		249	485		252	482
Age (years)	12.51 (0.28)	12.53 (0.28)	0.46	12.49 (0.34)	12.50 (0.27)	0.56	15.47 (0.30)	15.48 (0.28)	0.61	15.51 (0.29)	15.48 (0.29)	0.15
Height (cm)	149.8 (7.9)	152.3 (7.7)	<0.001	150.8 (7.5)	153.7 (7.1)	<0.001	169.0 (7.1)	172.0 (7.9)	<0.001	160.6 (5.9)	162.5 (5.8)	<0.001
Weight (kg)	42.6 (9.4)	45.3 (10.4)	<0.001	44.0 (9.0)	48.2 (10.7)	<0.001	58.6 (9.4)	61.1 (11.7)	0.002	56.6 (8.5)	58.1 (10.1)	0.03
Body mass index (kg/m2)	18.9 (3.3)	19.4 (3.4)	0.06	19.2 (2.9)	20.3 (3.6)	<0.001	20.4 (2.5)	20.6 (3.3)	0.44	21.9 (3.1)	22.0 (3.4)	0.85
No (%) of self-reported smokers	8 (3)	32 (6)	0.14	4 (2)	25 (5)	0.046	52 (21)	101 (21)	1.00	41 (16)	127 (26)	0.003
Predicted VO2 max (ml/kg/min)*	45.3 (5.3)	46.5 (6.4)	0.006	40.0 (5.3)	39.8 (6.9)	0.68	51.1 (6.0)	53.6 (6.9)	<0.001	40.4 (5.4)	41.3 (6.9)	0.08
Physical activity†	33.5 (14.3)	31.5 (15.6)	0.085	24.5 (13.2)	22.0 (13.6)	0.015	27.2 (15.8)	26.7 (14.5)	0.73	17.2 (12.0)	18.1 (12.9)	0.32
Reported birth weight (g)	3384 (601)	3479 (560)	0.042	3307 (512)	3358 (511)	0.21	3438 (558)	3433 (597)	0.92	3357 (513)	3358 (524)	0.98
No (%) of sexual maturity‡	226 (90)	488 (92)	0.39	139 (56)	319 (62)	0.13	22 (9)	0	<0.001	0	0	0.55
No (%) breast fed	50 (20)	159 (30)	0.003	57 (23)	159 (31)	0.029	37 (15)	150 (31)	<0.001	33 (13)	174 (36)	<0.001
No (%) of non-manual social class	146 (58)	381 (72)	<0.001	156 (63)	370 (72)	0.026	147 (59)	369 (76)	<0.001	139 (55)	347 (72)	<0.001

^*Oxygen consumption at maximal dynamic effort in 20 m shuttle run.

^†Scores up to 100.

^‡Tanner I-III.