Child participant demographics (N=1781)
| Cases (n=1179) | Siblings (n=602) | |
| Age at enrolment* | 11.3 (SD: 4.3) | 10.1 (SD: 5.3) |
| Sex | ||
| Male | 676 (57%) | 317 (53%) |
| Female | 502 (43%) | 285 (47%) |
| Neither | 1 (<1%) | 0 |
| Singleton versus multiple gestation birth | ||
| Singleton | 1105 (94%) | 561 (93%) |
| Twin | 56 (5%) | 33 (5%) |
| Triplet | 5 (<1%) | 2 (<1%) |
| Unknown | 13 (1%) | 6 (1%) |
| Highest grade completed at enrolment | ||
| Never attended/kindergarten only | 158 (13%) | 168 (28%) |
| First | 87 (7%) | 41 (7%) |
| Second | 94 (8%) | 38 (6%) |
| Third | 109 (9%) | 33 (5%) |
| Fourth | 112 (10%) | 35 (6%) |
| Fifth | 111 (9%) | 43 (7%) |
| Sixth | 103 (9%) | 48 (8%) |
| Seventh | 101 (9%) | 32 (5%) |
| Eighth | 78 (7%) | 44 (7%) |
| At least ninth | 226 (19%) | 120 (20%) |
| Family’s total income (before taxes) during the 12 months before the child was born, including wages, salaries, social security, retirement benefits, help from relatives, etc. | ||
| US$0–US$16 000 | 16 (1%) | 13 (2%) |
| US$16 001–US$20 000 | 7 (1%) | 3 (<1%) |
| US$20 001–US$24 000 | 15 (1%) | 1 (<1%) |
| US$24 001–US$28 000 | 11 (1%) | 5 (1%) |
| US$28 001–US$32 000 | 19 (2%) | 9 (2%) |
| US$32 001–US$40 000 | 39 (3%) | 26 (4%) |
| US$40 001–US$48 000 | 42 (4%) | 20 (3%) |
| US$48 001–US$57 000 | 50 (4%) | 28 (5%) |
| US$57 001–US$60 000 | 44 (4%) | 20 (3%) |
| US$60 001–US$73 000 | 79 (7%) | 31 (5%) |
| US$73 001–US$85 000 | 104 (9%) | 52 (9%) |
| US$85 001–US$100 000 | 137 (12%) | 78 (13%) |
| US$100 001–US$125 000 | 152 (13%) | 69 (11%) |
| US$125 001–US$150 000 | 102 (9%) | 69 (11%) |
| US$150 001–US$175 000 | 88 (7%) | 29 (5%) |
| US$175 001–US$200 000 | 41 (3%) | 18 (3%) |
| US$200 001–US$250 000 | 50 (4%) | 22 (4%) |
| US$250 001–US$300 000 | 22 (2%) | 10 (2%) |
| US$300 000 or more | 34 (3%) | 28 (5%) |
| Missing /I prefer not to respond | 127 (11%) | 71 (12%) |
| Insurance † | ||
| Private insurance | 913 (80%) | NA |
| Medicaid | 145 (13%) | NA |
| Canadian government healthcare | 96 (8%) | NA |
| Race | ||
| White (ie, European, Middle Eastern, Northern Africa, etc) | 983 (95%) | 516 (95%) |
| More than one race or origin | 137 (12%) | 58 (10%) |
| Asian (ie, Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, Hmong, Laotian, Thai, Pakistani, Cambodian, etc) | 23 (2%) | 14 (3%) |
| Black or African American (ie, African American, Haitian, Nigerian, etc) | 3 (<1%) | 2 (<1%) |
| American Indian or Alaskan Native (ie, Navajo, Mayan, Tlingit, etc) | 9 (1%) | 2 (<1%) |
| Native Hawaiian or other Pacific Islander (ie, Native Hawaiian, Guamanian or Chamorro, Samoan, Fijian, Tongan, etc) | 1 (<1%) | 0 |
| Other race or origin | 4 (<1%) | 3 (<1%) |
| Missing | 2 | 0 |
| Ethnicity | ||
| Hispanic, Latino or Spanish origin (ie, Mexico, Mexican American, Puerto Rican, Cuban, Argentinian, Colombian, Dominican, Nicaraguan, Salvadorian, Spaniard, etc) | 84 (7%) | 34 (6%) |
n (%) or mean (SD).
*Missing n=6 sibling date of births.
†Missing n=35 cases; ≤3% of cases reported coverage from each of the following: Medicare, Medi-gap, SCHIP (CHIP/Children’s Health Insurance Program), Military healthcare (Tricare/VA/CHAMP-VA), Indian Health Service, State-sponsored health plan, other government programme, single service plan (eg, dental, vision, prescriptions), no coverage of any kind, other coverage (not listed here).