Table 1 Subject demographic characteristics

Age (years)^a

P < 0.001^*

P = 0.111

9.13 ± 3.63

12.74 ± 2.84

10.53 ± 3.73

10.32 ± 3.80

Grades^b

P < 0.001^*

P = 0.851

 Kindergarten

567 (96.10%)

23 (3.90%)

438 (18.20%)

152 (18.40%)

 Primary grades 1–3

705 (82.50%)

150 (17.50%)

644 (26.70%)

211 (25.50%)

 Primary grades 4–6

317 (60.70%)

205 (39.30%)

380 (15.70%)

142 (17.20%)

 Junior high schools

392 (44.80%)

483 (55.20%)

657 (27.20%)

218 (26.40%)

 Senior high schools

146 (36.70%)

252 (63.30%)

294 (12.20%)

104 (12.60%)

Gender^b

P < 0.001^*

P = 0.134

 Male

1111 (69.90%)

478 (30.10%)

1202 (49.80%)

387 (46.80%)

 Female

1016 (61.50%)

635 (38.50%)

1211 (50.20%)

440 (53.20%)

Whether myopic^b

P = 0.005^*

 non-myopia

796 (33.00%)

317 (38.30%)

 myopia

1617 (67.00%)

510 (61.70%)

Region^b

P = 0.005^*

 Urban

1617 (67.00%)

796 (33.00%)

 Rural

510 (61.70%)

317 (38.30%)

Whether parents are myopic^b

P < 0.001^*

P < 0.001^*

 No

1073 (68.90%)

484 (31.10%)

982 (40.70%)

575 (69.50%)

 Yes

1054 (62.60%)

629 (37.40%)

1431 (59.30%)

252 (30.50%)

Sleep time per day^b

P < 0.001^*

P = 0.119

 ≥ 10 h

344 (84.50%)

63 (15.50%)

294 (12.20%)

113 (13.70%)

 8–9 h

1462 (71.60%)

581 (28.40%)

1510 (62.60%)

533 (64.40%)

 < 8 h

321 (40.60%)

469 (59.40%)

609 (25.20%)

181 (21.90%)

Time spent using electronics per day^b

P < 0.001^*

P = 0.004^*

 < 30 min

915(71.30%)

369(28.70%)

994(41.20%)

290(35.10%)

 30 min–1 h

669(68.70%)

305(31.30%)

716(29.70%)

258(31.20%)

 1–2 h

342(59.60%)

232(40.40%)

422(17.50%)

152(18.40%)

 > 2 h

201(49.30%)

207(50.70%)

281(11.60%)

127(15.40%)

Eye health behavior levels^b

P < 0.001^*

P = 0.002^*

 Good

654(56.40%)

505(43.60%)

408(16.90%)

179(21.60%)

 Moderate

1009(67.50%)

485(32.50%)

1108(45.90%)

386(46.70%)

 Poor

464(79.00%)

123(21.00%)

897(37.20%)

262(31.70%)