Characteristics of children in the Border Air Quality Study [22] born between 1999 and 2002 meeting the asthma case definition, their age- and sex-matched controls, and nonasthmatic children by time window
| Pre-school | School age | |||||
| Cases | Controls | Nonasthmatics | Cases | Controls | Nonasthmatics | |
| Subjects | 6948 | 34 621 | 58 306 | 1711 | 8577 | 63 543 |
| Sex | ||||||
| Female | 2646 (38) | 13 143 (38) | 31 591 (50) | 690 (40) | 3480 (41) | 30 901 (49) |
| Male | 4302 (62) | 21 478 (62) | 33 663 (50) | 1021 (60) | 5097 (59) | 32 642 (51) |
| Breastfeeding at discharge | ||||||
| No breastfeeding | 545 (8) | 2430 (7) | 4632 (7) | 141 (8) | 626 (7) | 4491 (7) |
| Breastfeeding | 6358 (92) | 32 028 (93) | 60 296 (93) | 1561 (92) | 7911 (93) | 58 735 (93) |
| Unknown | 45 (0) | 163 (0) | 326 (0) | 9 (1) | 40 (0) | 317 (0) |
| Maternal post-secondary education quartiles | ||||||
| 1 (lowest) | 1882 (27) | 7670 (22) | 14 441 (23) | 459 (27) | 1959 (22) | 13 982 (22) |
| 2 | 1622 (23) | 7973 (23) | 14 776 (23) | 411 (23) | 1996 (23) | 14 365 (23) |
| 3 | 1781 (26) | 9407 (27) | 17 792 (26) | 421 (26) | 2270 (27) | 17 371 (27) |
| 4 | 1663 (24) | 9571 (28) | 18 245 (27) | 420 (24) | 2352 (28) | 17 825 (28) |
| Area-based household income quintiles | ||||||
| 1 (poorest) | 1693 (24) | 7468 (22) | 13 950 (21) | 392 (23) | 1833 (21) | 13 558 (21) |
| 2 | 1697 (24) | 7719 (22) | 14 446 (22) | 425 (25) | 1905 (22) | 14 021 (22) |
| 3 | 1460 (21) | 7178 (21) | 17 792 (21) | 377 (22) | 1893 (21) | 13 344 (22) |
| 4 | 1185 (17) | 6799 (20) | 12 654 (20) | 301 (18) | 1629 (19) | 12 353 (19) |
| 5 | 913 (13) | 5457 (16) | 10 413 (16) | 216 (13) | 1317 (16) | 10 267 (15) |
| Parity | ||||||
| 0 | 3332 (52) | 15 504 (45) | 29 602 (45) | 892 (48) | 3879 (45) | 28 710 (45) |
| 1+ | 3616 (48) | 19 117 (55) | 35 652 (55) | 819 (52) | 4698 (55) | 34 833 (55) |
| Gestation length weeks | 38.9±1.94 | 39.4±1.15 | 39.1±1.66 | 39.0±1.8 | 39.1±1.68 | 39.1±1.69 |
| Maternal age years | 31.2±5.09 | 31.5±5.06 | 31.4±5.07 | 30.8±5.3 | 31.5±5.12 | 31.4±5.06 |
| Birthweight g | 3362±567 | 3510±458 | 3447±533 | 3385±538 | 3437±527 | 3431±533 |
Data are presented as n, n (%) or mean±sd.