Table 1. Characteristics of the Study Participants According to ADHD Status.
| Characteristic | Participants, No. (%) (N = 59 754) | P Value | |
|---|---|---|---|
| Children With ADHD (n = 2566) | Children Without ADHD (n = 57 188) | ||
| Age, y | |||
| 2-6 | 197 (7.7) | 9626 (16.8) | <.001 |
| 7-17 | 2369 (92.3) | 47 562 (83.2) | |
| Sex | |||
| Male | 1647 (64.2) | 28 613 (50.0) | <.001 |
| Female | 919 (35.8) | 28 575 (50.0) | |
| Parental education level, y | |||
| ≤9 | 986 (38.4) | 14 982 (26.2) | <.001 |
| >9 | 1580 (61.6) | 42 206 (73.8) | |
| Annual household income, Yuana | |||
| ≤30 000 | 1705 (66.5) | 32 924 (57.6) | <.001 |
| >30 000 | 861 (33.6) | 24 264 (42.4) | |
| Type of home district | |||
| Residential | 2206 (86.0) | 50 214 (87.8) | .01 |
| Industrial or business | 360 (14.0) | 6974 (12.2) | |
| Dog ownership | |||
| No | 2377 (92.6) | 54 003 (94.4) | <.001 |
| Yes | 189 (7.4) | 3185 (5.6) | |
| Cigarette smoking during pregnancy | |||
| No | 2527 (98.5) | 56 860 (99.4) | <.001 |
| Yes | 39 (1.5) | 328 (0.6) | |
| Alcohol drinking during pregnancy | |||
| No | 2522 (98.3) | 56 783 (99.3) | <.001 |
| Yes | 44 (1.7) | 405 (0.7) | |
| Breastfeeding | |||
| No | 888 (34.6) | 19 110 (33.4) | .21 |
| Yes | 1678 (65.4) | 38 078 (66.6) | |
| No. of siblings | |||
| 0 | 2112 (82.3) | 48 458 (84.7) | .001 |
| ≥1 | 454 (17.7) | 8730 (15.3) | |
| Low birth weight | |||
| No | 2454 (95.6) | 55 113 (96.4) | .05 |
| Yes | 112 (4.4) | 2075 (3.6) | |
| Preterm birth | |||
| No | 2378 (92.7) | 54 159 (94.7) | <.001 |
| Yes | 188 (7.3) | 3029 (5.3) | |
| Normalized difference vegetation index | |||
| Within 100 m of school or kindergarten, median (IQR) | 0.26 (0.21-0.35) | 0.27 (0.22-0.38) | <.001 |
| Within 500 m of school or kindergarten, median (IQR) | 0.27 (0.23-0.33) | 0.30 (0.24-0.38) | <.001 |
| Within 1000 m of school or kindergarten, median (IQR) | 0.27 (0.23-0.33) | 0.30 (0.24-0.36) | <.001 |
| Soil-adjusted vegetation index | |||
| Within 100 m of school or kindergarten, median (IQR) | 0.14 (0.11-0.20) | 0.16 (0.12-0.22) | <.001 |
| Within 500 m of school or kindergarten, median (IQR) | 0.15 (0.12-0.20) | 0.17 (0.14-0.21) | <.001 |
| Within 1000 m of school or kindergarten, median (IQR) | 0.15 (0.13-0.19) | 0.16 (0.14-0.20) | <.001 |
Abbreviations: ADHD, attention-deficit/hyperactivity disorder; IQR interquartile range.
a
As of November 25, 2019, to convert Yuan to US dollars, multiply by 0.14.