Table 1.
Subject Characteristics Among Three U.S. Geographic Regions
| All (N = 376) | CA (N = 125) | MA (N = 126) | OH/IL (N = 125) | Comparison (p-value) | |
|---|---|---|---|---|---|
| n (%) | |||||
| Race/ethnicity | <0.001 | ||||
| Non-Hispanic white | 137 (37%) | 43 (34%) | 23 (18%) | 71 (29%) | |
| Non-Hispanic black | 114 (31%) | 13 (10%) | 80 (63%) | 21 (18%) | |
| Hispanic | 39 (11%) | 18 (14%) | 7 (6%) | 14 (12%) | |
| Asian | 60 (16%) | 45 (36%) | 9 (7%) | 6 (5%) | |
| Native American | 6 (2%) | 1 (1%) | 5 (4%) | 0 | |
| Other | 15 (4%) | 5 (4%) | 2 (2%) | 8 (7%) | |
| Birthplace | <0.001 | ||||
| US | 221 (59%) | 72 (58%) | 53 (42%) | 96 (78%) | |
| Other | 153 (41%) | 53 (42%) | 73 (58%) | 27 (22%) | |
| Marital status | <0.001 | ||||
| Never married | 89 (24%) | 13 (11%) | 48 (38%) | 28 (23%) | |
| Married | 237 (64%) | 74 (60%) | 75 (60%) | 88 (72%) | |
| Divorced | 36 (10%) | 32 (26%) | 2 (2%) | 2 (2%) | |
| Widowed | 2 (1%) | 1 (1%) | 0 | 1 (1%) | |
| Other | 8 (2%) | 3 (2%) | 1 (1%) | 4 (3%) | |
| Highest education | <0.001 | ||||
| High school or below | 62 (17%) | 8 (7%) | 24 (19%) | 30 (24%) | |
| Vocation/trade school | 71 (19%) | 26 (21%) | 39 (31%) | 6 (5%) | |
| 2-yr college | 42 (11%) | 7 (6%) | 17 (13%) | 18 (15%) | |
| 4-yr college | 82 (22%) | 22 (18%) | 23 (18%) | 37 (30%) | |
| Grad or higher | 114 (31%) | 59 (48%) | 23 (18%) | 32 (26%) | |
| MVI use | 0.53 | ||||
| Yes | 285 (77%) | 99 (80%) | 93 (74%) | 93 (76%) | |
| No | 87 (23%) | 25 (20%) | 33 (26%) | 29 (24%) | |
| Smoking | 0.03 | ||||
| Yes | 19 (5%) | 2 (2%) | 6 (5%) | 11 (9%) | |
| No | 354 (95%) | 122 (98%) | 120 (95%) | 112 (91%) | |
| Use of supplemental baby formula by category | 0.04 | ||||
| None | 168 (45%) | 59 (48%) | 48 (38%) | 61 (50%) | |
| <12 ounces/day | 159 (43%) | 56 (45%) | 53 (42%) | 50 (41%) | |
| ≥12 ounces/day | 43 (12%) | 9 (7%) | 24 (19%) | 10 (8%) | |
| Dichotomous supplemental baby formula use | 0.03 | ||||
| Yes | 202 (45%) | 65 (52%) | 77 (62%) | 60 (50%) | |
| No | 168 (55%) | 59 (48%) | 48 (38%) | 61 (50%) | |
| Mean (SD) or Median (range) | |||||
| Mother's age (years) | 31.1 (5.6) | 32.7 (5.0) | 29.5 (5.8) | 31.1 (5.6) | <0.001 |
| GA at birth (weeks) | 38.6 (2.5) | 38.9 (2.4) | 39.3 (1.2) | 37.6 (3.3) | <0.001 |
| Baby age at enrollment (days) | 45.5 (6–1868) | 49.5 (12–1868) | 43.5 (10–672) | 44.5 (6–428) | <0.001 |
CA, subjects recruited in California; IL, subjects recruited in Illinois; GA, gestational age; MA, subjects recruited in Massachusetts; MVI, multivitamin supplements; OH, subjects recruited in Ohio; SD, standard deviation.