TABLE 4.
Characteristics of students in the present study in 2021 (Shenzhen, China. 2019–2021).
| Characteristic | No myopia (n = 3,654) | Myopia (n = 3,943) | Statistical value | P |
|---|---|---|---|---|
| Sex, n (%) | ||||
| Boy | 2,103 (51.0) | 2,020 (49.0) | χ 2 = 30.56 | <0.001 |
| Girl | 1,551 (44.6) | 1,923 (55.4) | ||
| Age, mean (SD), years | 9.21 (2.18) | 11.41 (1.94) | t = −12.10 | <0.001 |
| Parental myopia, n (%) | ||||
| 0 parent | 2,420 (51.4) | 2,288 (48.6) | χ 2 = 72.60 | <0.001 |
| 1 parent | 843 (45.8) | 999 (54.2) | ||
| 2 parents | 391 (37.3) | 656 (62.7) | ||
| Time of birth, n (%) | ||||
| Premature infant | 254 (45.8) | 300 (54.2) | χ 2 = 1.21 | 0.27 |
| Normal term infant | 3,400 (48.3) | 3,643 (51.7) | ||
| Parental education, n (%) | ||||
| High school and below | 1,101 (50.0) | 1,099 (50.0) | χ 2 = 4.71 | 0.03 |
| Junior college and above | 2,553 (47.3) | 2,844 (52.7) | ||
| Average monthly income, yuan, n (%) | ||||
| <10,000 | 1,862 (49.3) | 1,917 (50.7) | χ 2 = 3.69 | 0.16 |
| 10,000–49,999 | 1,470 (47.1) | 1,651 (52.9) | ||
| ≥50,000 | 332 (47.0) | 375 (53.0) | ||
| Average living space, square meters, n (%) | ||||
| <20 | 1,295 (48.9) | 1,354 (51.1) | χ 2 = 3.08 | 0.38 |
| 20–29 | 1,004 (46.4) | 1,160 (53.6) | ||
| 30–39 | 704 (47.5) | 779 (52.5) | ||
| ≥40 | 626 (48.1) | 675 (51.9) | ||
| Sleep time per day, hours (%) | ||||
| <8 | 763 (34.8) | 1,432 (65.2) | χ 2 = 264.52 | <0.001 |
| 8–9 | 2,190 (51.3) | 2,078 (48.7) | ||
| >9 | 711 (62.2) | 433 (37.8) | ||
| Digital device exposure per day, hours (%) | ||||
| <0.5 | 1,444 (53.7) | 1,243 (46.3) | χ 2 = 64.22 | <0.001 |
| 0.5–1 | 1,325 (47.1) | 1,490 (52.9) | ||
| >1 | 885 (42.2) | 1,210 (57.8) | ||
| Time spent performing outdoor activities per day, mean (SD), hours | 2.68 (1.47) | 1.14 (1.01) | t = 8.14 | <0.001 |
| Baseline SER of the right eye, mean (SD), D | −0.08 (0.81) | −2.45 (1.75) | t = 19.48 | <0.001 |
SD, standard deviation; SER, spherical equivalent refraction; D, diopters.