Table 2.

Characteristics of the total study population and the population separated by survey wave: T0, baseline. T3, 6-year follow-up.

Variables		Mean	SD	T0: Mean	T0: SD	T3: Mean	T3: SD
Age	years	9.4	3.4	6.2	1.8	12.0	1.8
BMI-z-score*		0.32	1.08	0.17	1.07	0.45	1.07
Waist-to-height-ratio		0.44	0.05	0.46	0.04	0.43	0.05
UVDVC	kJ/m2	1.8	2.0	1.6	2.0	2.0	2.0
Time spent outdoors	h/day	2.08	1.37	2.41	1.39	1.80	1.29
Vitamin D intake	µg/d	1.7	0.5	1.5	0.2	1.9	0.6
25-hydroxyvitamin D	nmol/l	45.2	16.7	44.7	15.4	45.6	17.8
		N	%	T0: N	T0: %	T3: N	T3: %
25-hydroxyvitamin D categories#	<50 nmol/l	2275	63	998	62	1277	64
	50–75 nmol/l	1208	33	562	35	646	32
	≥75 nmol/l	123	3	43	3	80	4
Sex	Boys	1855	51	823	51	1032	52
	Girls	1751	49	780	49	971	48
Country	Italy	353	10	94	6	259	13
	Estonia	603	17	286	18	317	16
	Cyprus	66	2	37	2	29	1
	Belgium	205	6	95	6	110	5
	Sweden	461	13	218	14	243	12
	Germany	560	16	216	13	344	17
	Hungary	826	23	389	24	437	22
	Spain	532	15	268	17	264	13
Weight status categories*	underweight	356	10	196	12	160	8
	normal weight	2564	71	1175	73	1389	69
	overweight	516	14	174	11	342	17
	obese	170	5	58	4	112	6
ISCED	low	138	4	51	3	87	4
	middle	1537	43	671	43	866	44
	high	1877	53	849	54	1028	52

ISCED international standard classification of education, UVDVC cloud-modified vitamin D UV dose of the second last month before blood draw

*Cole and Lobstein 2012 [23].

^#deficient (<50 nmol/l), insufficient (50-<75 nmol/l), sufficient (≥75 nmol/l).