Table 1 Sample characteristics, stratified by gender

 Age (years); mean (SD)

5.16 (0.87)

5.15 (0.88)

0.318

5.15 (0.87)

5.14 (0.89)

0.251

 Childhood overweight/ obesity

666 (20.3%)

469 (16.0%)

19.768***

418 (21.3%)

298 (15.7%)

19.508***

 Child’s sleep duration on weekdays (≥10 h./day)

557 (16.9%)

496 (16.8%)

0.013

377 (17.1%)

309 (16.3%)

.466

 Child’s sleep duration on weekends (≥10 h./day)

960 (29.3%)

980 (33.3%)

12.001^***

612 (31.1%)

620 (32.7%)

1.167

 Child’s screen exposure frequency (≥5 times./week)

436 (13.3%)

400 (13.6%)

0.134

250 (12.7%)

250 (13.1%)

0.204

 Child’s exercise frequency (≥1 h./day)

1450 (44.1%)

1225 (41.6%)

4.025^*

909 (46.0%)

803 (42.2%)

5.694^*

Family income ^#

0.265

0.993

  > 8000RMB

1705 (51.8%)

1519 (51.5%)

1030 (52.2%)

963 (50.6%)

 4000- 8000RMB

1228 (37.3%)

1117 (37.9%)

727 (36.8%)

728 (38.3%)

  < 4000RMB

356 (10.8%)

311 (10.6%)

218 (11.0%)

211 (11.1%)

Family structure

0.587

0.001

 Single parent

89 (2.7%)

81 (2.7%)

51 (2.6%)

49 (2.6%)

 Nuclear family

1864 (56.7%)

1697 (57.6%)

1141 (57.8%)

1098 (57.7%)

 Extended family

1336 (40.6%)

1169 (39.7%)

783 (39.6%)

755 (39.7%)

Mother’s education level

6.026*

4.590

 College and above

2442 (74.2%)

2243 (76.1%)

1464 (74.1%)

1458 (76.7%)

 Secondary education

509 (15.5%)

454 (15.4%)

310 (15.7%)

285 (15.0%)

 Primary education

338 (10.3%)

250 (8.5%)

201 (10.2%)

159 (8.4%)

Father’s education level

2.524

2.290

 College and above

2439 (74.2%)

2234 (75.8%)

1456 (73.7%)

1440 (75.7%)

 Secondary education

564 (17.1%)

482 (16.4%)

347 (17.6%)

316 (16.6%)

 Primary education

286 (8.7%)

231 (7.8%)

172 (8.7%)

146 (7.7%)

First-degree relative with allergies

897 (27.3%)

767 (26.0%)

1.234

471 (23.8%)

427 (22.5%)

1.064

 Gestational weeks

2.022

2.113

  Premature delivery

248 (7.6%)

202 (6.9%)

142 (7.2%)

124 (6.6%)

  Post-term delivery

128 (3.9%)

130 (4.5%)

69 (3.5%)

81 (4.3%)

  Term delivery

2890 (88.5%)

2589 (88.6%)

1754 (89.3%)

1679 (89.1%)

Delivery mode

6.525*

7.401**

 Cesarean delivery

1717 (52.2%)

1443 (49.0%)

1025 (51.9%)

904 (47.5%)

 Vaginal delivery/ midwifery

1572 (47.8%)

1504 (51.0%)

950 (48.1%)

998 (52.5%)

Mother’s age at delivery

0.612

1.101

  ≥ 30

1286 (39.6%)

1139 (39.2%)

765 (39.2%)

731 (39.0%)

 25–29

1458 (44.9%)

1332 (45.9%)

875 (44.8%)

864 (46.1%)

  ≤ 24

500 (15.4%)

433 (14.9%)

311 (15.9%)

278 (14.8%)

Full breastfeeding ≥6 month

1885 (57.3%)

1754 (59.5%)

3.112

1151 (58.3%)

1117 (58.7%)

0.081

Gestational smoking exposure

71 (2.2%)

63 (2.1%)

0.003

35 (1.8%)

39 (2.1%)

0.401

Gestational drinking

84 (2.6%)

2878 (97.7%)

0.294

47 (2.4%)

46 (2.4%)

0.006

Gestational hypertension

60 (1.8%)

85 (2.9%)

7.690**

33 (1.7%)

45 (2.4%)

2.374

Gestational diabetes

149 (4.5%)

142 (4.8%)

0.290

87 (4.4%)

82 (4.3%)

0.020

Gestational anemia

189 (5.7%)

200 (6.8%)

2.875

113 (5.7%)

124 (6.5%)

1.075

Pre-pregnancy overweight/obesity

328 (10.0%)

267 (9.1%)

1.453

203 (10.3%)

163 (8.6%)

3.269

 Farmlands and orchards

574 (17.5%)

518 (17.6%)

.017

329 (16.7%)

305 (16.0%)

0.274

 Chemical emission sources

82 (2.5%)

87 (3.0%)

1.242

45 (2.3%)

48 (2.5%)

0.249

 Smog-emitting factory

79 (2.4%)

91 (3.1%)

2.758

41 (2.1%)

56 (2.9%)

2.995

 Large garbage dump

232 (7.1%)

208 (7.1%)

.000

136 (6.9%)

129 (6.8%)

.898

 Asthma

533 (16.2%) ^a

380 (12.9%) ^a

13.635***

150 (7.6%) ^b

78 (4.1%) ^b

21.370***

 Wheeze

586 (17.8%) ^a

427 (14.5%) ^a

12.650***

165 (8.4%) ^b

90 (4.7%) ^b

20.693***

 Allergic rhinitis

802 (24.4%) ^a

509 (17.3%) ^a

47.357***

225 (11.4%) ^b

129 (6.8%) ^b

24.818***