TABLE 1.

Demographic Characteristics of Children With and Without SSC at Age 7

Characteristic	Control Group, N = 183		Case Group, N = 182
	N	%	N	%
Age, y
<7.5	144	78.7	124	68.1
>7.5	39	21.3	58	31.9
Gender
Female	69	37.7	68	37.4
Male	114	62.3	114	62.6
Grade levela
<1	2	1.1	3	1.7
1	130	71.0	110	60.4
2	37	20.2	56	30.8
≥3	9	4.9	9	4.9
Race or ethnicityb
Nonwhite or Hispanic	47	25.7	37	20.3
White, non-Hispanic	136	74.3	145	79.7
SES
I (highest)	53	29.0	43	23.6
II	102	55.7	81	44.5
III	15	8.2	36	19.8
IV	11	6.0	20	11.0
V (lowest)	2	1.1	2	1.1
Site
Seattle	71	38.8	74	40.7
Chicagoc	76	41.5	66	36.3
St Louis	9	4.9	18	9.9
Atlanta	27	14.8	24	13.2

^aGrade level missing for 5 control and 4 case participants.

^bIncludes Hispanic or Latino ethnicity, Asian or Pacific Islander, black or African American, and mixed races or ethnicities.

^cIncludes children from Philadelphia, who were assessed by staff from the Chicago site.