Table 1.

Characteristics of study participants by the number of siblings

Variables	None (only child)		One		Two or more		Total		χ2	P valuea
	N	%	N	%	N	%	N	%
Sex									32.94	< 0.001
Boy	26,351	53.67	3457	50.45	6027	51.85	35,835	53.03
Girl	22,746	46.33	3395	49.55	5598	48.15	31,739	46.97
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00
Birth weight (g)									4.77	0.029
< 2500	1631	3.32	417	6.09	939	8.08	2987	4.42
2500–4000	41,584	84.70	5532	80.74	8712	74.94	55,828	82.62
≥ 4000	4883	9.95	722	10.54	1393	11.98	6998	10.36
Missing	999	2.03	181	2.64	581	5.00	1761	2.61
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00
Feeding patterns									8475.14	< 0.001
Breast Feeding	21,893	44.59	3546	51.75	7411	63.75	32,850	48.61
Formulary Feeding	7957	16.21	1054	15.38	1674	14.40	10,685	15.81
Mixed Feeding	18,965	38.63	2194	32.02	2391	20.57	23,550	34.85
Missing	282	0.57	58	0.85	149	1.28	489	0.72
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00
Workday TV time (hour/day)									41,614.76	< 0.001
< 1	29,037	59.14	3762	54.90	5484	47.17	38,283	56.65
1–3	18,353	37.38	2843	41.49	5534	47.60	26,730	39.56
> 3	990	2.02	135	1.97	303	2.61	1428	2.11
Missing	717	1.46	112	1.63	304	2.62	1133	1.68
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00
Internet use time (hour/week)									33,821.76	< 0.001
< 2	30,086	61.28	4518	65.94	7930	68.22	42,534	62.94
2–4	11,235	22.88	1346	19.64	1742	14.98	14,323	21.20
≥ 4	6301	12.83	717	10.46	769	6.62	7787	11.52
Missing	1475	3.00	271	3.96	1184	10.18	2930	4.34
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00
Snack frequency (times/day)									37,680.69	< 0.001
0	14,854	30.25	1951	28.47	2716	23.36	19,521	28.89
1–3	30,643	62.41	4355	63.56	7724	66.44	42,722	63.22
> 3	2994	6.10	458	6.68	846	7.28	4298	6.36
Missing	606	1.23	88	1.28	339	2.92	1033	1.53
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00
Father’s age at child birth (years)									976.81	< 0.001
< 25	7217	14.70	1119	16.33	2263	19.47	10,599	15.69
25–34	33,800	68.84	4078	59.52	6264	53.88	44,142	65.32
≥ 35	4918	10.02	1142	16.67	1902	16.36	7962	11.78
Missing	3162	6.44	513	7.49	1196	10.29	4871	7.21
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00
Mother’s age at child birth (years)									1518.61	< 0.001
< 25	15,672	31.92	2092	30.53	3872	33.31	21,636	32.02
25–34	30,882	62.90	3985	58.16	5933	51.04	40,800	60.38
≥ 35	1409	2.87	571	8.33	1173	10.09	3153	4.67
Missing	1134	2.31	204	2.98	647	5.57	1985	2.94
Total	49,097	100.00	6852	100.00	11,625	100.00	67,574	100.00

^aP Value from Chi-squared test