Table 1.
Participants’ Demographic Characteristics at the Three Time Points (n = 2,250)
| 2018 | 2019 | 2020 | |
|---|---|---|---|
| Age, M(SD) | 15.01 (0.03) | 16.1 (0.03) | 17.1 (0.03) |
| Gender (male) | 1199 (53.4%) | - | - |
| Smartphone possession | |||
| Owned | 2203 (97.9%) | 2221 (98.7%) | 2230 (99.1%) |
| Using family member’s smartphone | 47 (2.1%) | 29 (1.3%) | 20 (0.9%) |
| Hours of Smartphone use | |||
| Weekdays | |||
| Never | 36 (1.6%) | 25 (1.1%) | 24 (1.1%) |
| < 30 min | 135 (6.0%) | 115 (5.1%) | 60 (2.7%) |
| 30 min–1 h | 351 (15.6%) | 362 (16.1%) | 335 (14.9%) |
| 1–2 h | 695 (30.9%) | 700 (31.1%) | 693 (30.8%) |
| 2–3 h | 563 (25.0%) | 563 (25.0%) | 504 (22.4%) |
| 3–4 h | 227 (10.1%) | 235 (10.5%) | 261 (11.6%) |
| > 4 h | 243 (10.8%) | 250 (11.1%) | 373 (16.6%) |
| Weekends | |||
| Never | 50 (2.2%) | 36 (1.6%) | 16 (0.7%) |
| < 30 min | 97 (4.3%) | 56 (2.5%) | 34 (1.5%) |
| 30 min − 1 h | 196 (8.7%) | 173 (7.7%) | 126 (5.6%) |
| 1 − 2 h | 394 (17.5%) | 414 (18.4%) | 493 (21.9%) |
| 2 − 3 h | 585 (26.0%) | 630 (28.0%) | 598 (26.6%) |
| 3 − 4 h | 412 (18.3%) | 423 (18.8%) | 333 (14.8%) |
| > 4 h | 516 (22.9%) | 518 (23.0%) | 650 (28.9%) |
Notes. M, mean; SD, standard deviation