Table 9.

Demographic, socioenvironmental, and developmental variables of all participants according to income

Variables	All		Low income			High income					P value
	n	Mean ± SD or %	n	Mean ± SD or %				n	Mean ± SD or %
Height	243	150.83 ± 11.39	52		147.98 ± 12.43		191			151.6 ± 11.00		0.042
Weight	243	44.29 ± 12.06	52		41.13 ± 12.22		191			45.15 ± 11.90		0.033
NS	900	3.32 ± 2.03	221		3.37 ± 1.98		684			3.30 ± 2.05		0.566
Noise level (Ldn)	762	56.82 ± 9.38	187		55.47 ± 10.98		575			57.26 ± 8.77		0.024
Educational level of father												<0.001
Less than high school	2	0.2%	2		0.9%		0			0.0%
High school diploma	177	20.0%	82		38.3%		95			14.1%
Associate’s degree	159	17.9%	48		22.4%		111			16.5%
Bachelor’s degrees	423	47.7%	72		33.6%		351			52.2%
More than Master’s degrees	126	14.2%	10		4.7%		116			17.2%
Educational level of mother												<0.001
Less than high school	2	0.2%	1		0.5%		1			0.1%
High school diploma	197	22.0%	85		39.7%		112			16.4%
Associate’s degree	202	22.5%	63		29.4%		139			20.4%
Bachelor’s degrees	427	47.6%	60		28.0%		367			53.7%
More than Master’s degrees	69	7.7%	5		2.3%		64			9.4%
Distance to nearest road												0.015
Neighboring road	195	21.6%	36		16.2%		159			23.3%
<50 m	215	23.8%	49		22.1%		166			24.3%
>50 m, ≤100 m	292	32.3%	79		35.6%		213			31.2%
>100 m, ≤500 m	187	20.7%	56		25.2%		131			19.2%
≥500 m	15	1.7%	2		0.9%		13			1.9%
Father’s age at birth (years)	885	32.75 ± 3.84	210		32.41 ± 4.05		675			32.86 ± 3.77		0.139
Mother’s age at birth (years)	896	30.26 ± 3.74	214		29.70 ± 4.05		682			30.44 ± 3.62		0.012
Breast feeding												0.488
No	330	36.5%	76		34.5%		254			37.1%
Yes	574	63.5%	144		65.5%		430			62.9%
Smoking status of father												0.009
Never smoker	337	37.3%	65		29.8%		272			39.7%
Former smoker	244	27.0%	63		28.9%		181			26.4%
Current smoker	322	35.7%	90		41.3%		232			33.9%
Smoking status of mother												0.06
Never smoker	892	98.8%	215		97.7%		677			99.1%
Former smoker	6	0.7%	2		0.9%		4			0.6%
Current smoker	5	0.6%	3		1.4%		2			0.3%
Passive smoking
No	779	86.3%	177		80.8%		602			88.0%		0.007
Yes	124	13.7%	42		19.2%		82			12.0%
Smartphone usage												0.002
Never	115	12.7%	27		12.2%		88			12.9%
<1 h	374	41.4%	66		29.9%		308			45.1%
1–3 h	306	33.8%	96		43.4%		210			30.7%
3–5 h	90	10.0%	23		10.4%		67			9.8%
≥5 h	19	2.1%	9		4.1%		10			1.5%
Computer/video game usage												<0.001
Never	100	11.1%	17		7.7%		83			12.2%
<1 h	462	51.3%	87		39.4%		375			55.1%
1–3 h	289	32.1%	96		43.4%		193			28.4%
3–5 h	42	4.7%	17		7.7%		25			3.7%
≥5 h	8	0.9%	4		1.8%		4			0.6%

CI = confidence interval, Ldn = day–night equivalent level, NS = noise sensitivity, OR = odds ratio.