. 2017 Sep 18;125(9):097016. doi: 10.1289/EHP694

Table 1.

Description of characteristics of the study participants at birth and in 4- and 7-year follow-ups.

Characteristics	Birth	4–5-y follow-up		p-Value^c	p-Value^a	7-y follow-up		p-Value^c	p-Value^d	p-Value^e
Characteristics	Birth	Include^a ( $n = 888$ )	Excluded^b ( $n = 311$ )	p-Value^c	p-Value^a	Include^a ( $n = 978$ )	Excluded^b ( $n = 66$ )	p-Value^c	p-Value^d	p-Value^e
Sex (Female)	48.0%	48.8%	46.1%	0.39	0.73	48.8%	40.9%	0.21	0.72	0.99
Preterm birth (yes)	4.4%	3.7%	3.9%	0.89	0.42	3.4%	7.7%	0.08	0.21	0.70
Maternal educational attainment				0.04	0.01			0.21	$< 0.01$	0.81
No or primary school	31.0%	26.1%	29.9%			24.7%	30.8%
Secondary school	43.0%	42.7%	46.4%			43.6%	47.7%
University	26.1%	31.2%	23.7%			31.7%	21.5%
Maternal IQ^f	10.5 (3.7)	10.5 (4.4)	10.5 (4.4)	0.53	0.84	10.5 (4.4)	10.5 (4.7)	0.66	0.30	0.40
Maternal smoking during pregnancy (yes)	35.6%	33.6%	33.1%	0.88	0.32	31.7%	33.3%	0.78	0.04	0.38
Exposure to environmental tobacco smoke at 4-year follow-up (yes)	***	50.2%	47.7%	0.44	***	51.2%	48.4%	0.67	***	0.69
Exposure to environmental tobacco smoke at 7-year follow-up (yes)	***	***	***	***	***	30.3%	15.2%	0.01	***	***
Neighborhood socioeconomic status^g	0.6 (0.2)	0.6 (0.2)	0.7 (0.3)	0.33	0.22	0.6 (0.2)	0.6 (0.2)	0.12	0.09	0.65

Note: p-Values are reported for chi-squared test for categorical variables and Mann–Whitney U test for continuous variables. For continuous variables, median (IQR) and for categorical variables count (percentage) of each category has been reported.

^{^a}

p-Value for the difference between children with available data at birth and those included at the 4-year follow-up.

^{^b}

Children participated in the 4-y follow-up but did not have data on K-CPT.

^{^c}

p-Value for the difference between children included and excluded in each follow-up.

^{^d}

p-Value for the difference between children with available data at birth and those included at the 7-year follow-up.

^{^e}

p-Value for the difference between children with available data at the 4-year follow-up and those included at 7-y follow-up.

^{^f}

Wechsler Adult Intelligence Scale (WAIS-IV), Similarities subscale.

^{^g}

Urban vulnerability index.