Table 1.
Covariate information for the children in the study [no. (%)].
| Characteristic | Asthmatic children (n = 3,482) | Nonasthmatic children in total cohort (n = 33,919) | Randomly selected controls (n = 17,410) |
|---|---|---|---|
| Male sex* | 2,222 (64) | 16,885 (50) | 11,110 (64) |
| Native status | 70 (2) | 528 (2) | 282 (2) |
| Has siblings* | 2,042 (59) | 18,844 (56) | 9,618 (55) |
| Breast-feeding initiation* | 2,920 (84) | 29,286 (86) | 14,915 (86) |
| Maternal smoking status | 268 (8) | 2,625 (8) | 1,400 (8) |
| Area-based income quintilea,* | |||
| 1 | 814 (23) | 7,072 (21) | 3,625 (21) |
| 2 | 822 (24) | 7,350 (22) | 3,784 (22) |
| 3 | 762 (22) | 7,283 (21) | 3,745 (22) |
| 4 | 591 (17) | 6,582 (19) | 3,370 (19) |
| 5 | 493 (14) | 5,632 (17) | 2,886 (17) |
| Area-based maternal education quartilea,* | |||
| 1 | 985 (28) | 8,083 (24) | 4,166 (24) |
| 2 | 913 (26) | 8,704 (26) | 4,480 (26) |
| 3 | 830 (24) | 8,668 (26) | 4,440 (26) |
| 4 | 754 (22) | 8,464 (25) | 4,324 (25) |
| Maternal age (years)* | 30.8 ± 5.2 | 31.0 ± 5.1 | 31.0 ± 5.1 |
| Birth weight (g)* | 3,510 ± 450 | 3,530 ± 460 | 3,539 ± 458 |
| Gestational length (weeks)* | 39.3 ± 1.2 | 39.4 ± 1.1 | 39.4 ± 1.1 |
Values are no. (%) or mean ± SD. Data are for children who met the case definition for asthma (two outpatient physician diagnoses within 12 months or one hospital diagnosis; first column), children in the total cohort who did not meet the asthma case definition (second column), and a randomly selected set of controls from the total cohort (five age- and sex-matched controls for each case; third column). The randomly selected controls were representative of the nonasthmatic cohort (with the exception of matched variables).
Percentages may not add to 100 because of rounding error.
Statistically significant difference (p < 0.05) between asthmatic and nonasthmatic children, chi-square test for frequencies and t-test for means.