Table 1 Sociodemographic characteristics
Variables | Grade 7 | Grade 8 | Grade 9 | Grade 10 | Grade 11 | Grade 12 | p-value |
|---|---|---|---|---|---|---|---|
(n: 7975) | (n: 7723) | (n: 8014) | (n: 7498) | (n: 7242) | (n: 7754) | ||
Age (in years) | 12.50 ± 0.51 | 13.52 ± 0.52 | 14.51 ± 0.52 | 15.51 ± 0.52 | 16.50 ± 0.52 | 17.47 ± 0.52 |  |
Gender, Girls | 3879 (48.6) | 3803 (49.2) | 3865 (48.2) | 3619 (48.3) | 3544 (48.9) | 3723 (48.0) | 0.637 |
School type |  < 0.01 | ||||||
 Co-educational school | 5878 (73.7) | 5664 (73.3) | 5900 (73.6) | 4377 (58.4) | 4204 (48.1) | 4491 (57.9) |  |
 Boys school | 1079 (13.5) | 1074 (13.9) | 1095 (13.7) | 1532 (20.4) | 1498 (20.7) | 1604 (20.7) | |
 Girls school | 1018 (12.8) | 985 (12.8) | 1019 (12.7) | 1589 (21.2) | 154 (21.3) | 1659 (21.4) | |
Multicultural family |  < 0.01 | ||||||
 Yes | 170 (2.8) | 130 (2.4) | 103 (1.9) | 62 (1.3) | 58 (1.3) | 57 (1.3) |  |
 No | 5803 (97.2) | 5213 (97.6) | 5213 (98.1) | 4617 (98.7) | 4256 (98.7) | 4371 (98.7) | |
Perceived academic performance |  < 0.01 | ||||||
 Upper | 1468 (18.4) | 1183 (15.3) | 1323 (16.5) | 737 (9.8) | 702 (9.7) | 829 (10.7) |  |
 Upper middle | 2493 (31.3) | 2068 (26.8) | 2083 (26.0) | 1753 (23.4) | 1665 (23.0) | 1857 (23.9) | |
 Middle | 2509 (31.5) | 2238 (29.0) | 2093 (26.1) | 2343 (31.2) | 2379 (32.9) | 2521 (32.5) | |
 Lower middle | 1143 (14.3) | 1616 (20.9) | 1768 (22.1) | 1861 (24.8) | 1773 (24.5) | 1844 (23.8) | |
 Lower | 362 (4.5) | 618 (8.0) | 747 (9.3) | 804 (10.7) | 723 (10.0) | 703 (9.1) | |
Perceived household economic status |  < 0.01 | ||||||
 Upper | 1303 (16.3) | 965 (12.5) | 874 (10.9) | 652 (8.7) | 597 (8.2) | 578 (7.5) |  |
 Upper middle | 2635 (33.0) | 2350 (30.4) | 2344 (29.2) | 2071 (27.6) | 1894 (26.2) | 1946 (25.1) | |
 Middle | 3425 (42.9) | 3638 (47.1) | 392 (48.8) | 3761 (50.2) | 3615 (49.9) | 3952 (51.0) | |
 Lower middle | 542 (6.8) | 661 (8.6) | 751 (9.4) | 842 (11.2) | 933 (12.9) | 1055 (13.6) | |
 Lower | 70 (0.9) | 109 (1.4) | 133 (1.7) | 172 (2.3) | 203 (2.8) | 223 (2.9) | |
Dietary behaviora (days) | 4.28 (± 2.74) | 4.04 (± 2.75) | 3.95 (± 2.77) | 4.02 (± 2.68) | 3.83 (± 2.68) | 4.01 (± 2.70) |  < 0.01 |
Perceived health status |  < 0.01 | ||||||
 Very healthy | 2438 (30.6) | 2134 (27.6) | 2292 (28.6) | 1932 (25.8) | 1714 (23.7) | 1860 (24.0) |  |
 Healthy | 3736 (46.8) | 3544 (45.9) | 3527 (44.0) | 3401 (45.4) | 3151 (43.5) | 3200 (41.3) | |
 Normal | 1528 (19.2) | 1667 (21.6) | 1715 (21.4) | 1604 (21.4) | 1753 (24.2) | 1933 (24.9) | |
 Unhealthy | 263 (3.3) | 358 (4.6) | 455 (5.7) | 532 (7.1) | 575 (7.9) | 712 (9.2) | |
 Very unhealthy | 10 (0.1) | 20 (0.3) | 25 (0.3) | 29 (0.4) | 49 (0.7) | 49 (0.6) | |
Perception of body shape |  < 0.01 | ||||||
 Very skinny | 332 (4.2) | 336 (4.4) | 359 (4.5) | 341 (4.5) | 293 (4.0) | 285 (3.7) |  |
 Skinny | 1802 (22.6) | 1756 (22.7) | 1770 (22.1) | 1582 (21.1) | 1465 (20.2) | 1480 (19.1) | |
 Average | 2944 (37.5) | 2898 (37.5) | 2965 (37.0) | 2680 (35.7) | 2572 (35.5) | 2727 (35.2) | |
 Obese | 2395 (30.0) | 2309 (29.9) | 2465 (30.8) | 2399 (32.0) | 2682 (34.6) | 2682 (34.6) | |
 Very obese | 452 (5.7) | 424 (5.5) | 455 (5.7) | 496 (6.6) | 514 (7.1) | 580 (7.5) | |
Physical activityb (in days) | 2.32 ± 2.21 | 2.26 ± 2.16 | 2.20 ± 2.19 | 1.83 ± 2.02 | 1.84 ± 2.01 | 1.69 ± 2.00 |  < 0.01 |
Time spent studying (WDc) (in mins) | 376.68 ± 242.87 | 415.80 ± 242.87 | 425.80 ± 237.63 | 520.05 ± 263.81 | 516.83 ± 251.16 | 550.70 ± 252.37 |  < 0.01 |
Time spent studying (WKd) (in mins) | 148.56 ± 155.73 | 186.37 ± 178.95 | 191.13 ± 187.34 | 266.74 ± 225.93 | 276.76 ± 232.37 | 339.08 ± 266.73 |  < 0.01 |
Duration of Internet use (WDc) (in mins) | 111.75 ± 112.57 | 122.82 ± 122.45 | 117.96 ± 120.20 | 104.29 ± 109.48 | 103.07 ± 110.23 | 97.73 ± 105.12 |  < 0.01 |
Duration of Internet use (WKd) (in mins) | 186.55 ± 163.00 | 208.39 ± 174.33 | 202.43 ± 176.93 | 189.43 ± 161.08 | 174.93 ± 161.61 | 163.74 ± 152.89 |  < 0.01 |
Perceived level of stress |  < 0.01 | ||||||
 Very much | 643 (8.1) | 754 (9.8) | 820 (10.2) | 822 (11.0) | 874 (12.1) | 976 (12.6) |  |
 A lot | 2021 (25.3) | 2156 (27.9) | 2143 (26.7) | 2166 (28.9) | 2175 (30.0) | 2264 (29.2) | |
 A little | 3276 (41.1) | 3204 (41.5) | 3407 (42.5) | 3203 (42.7) | 2991 (41.3) | 3223 (41.6) | |
 Not much | 1625 (20.4) | 1307 (16.9) | 1353 (16.9) | 1044 (13.9) | 989 (13.7) | 1057 (13.6) | |
 Not at all | 410 (5.1) | 302 (3.9) | 291 (3.6) | 263 (3.5) | 213 (2.9) | 234 (3.0) | |
Depressive symptoms, (yes) | 1752 (22.0) | 2075 (26.9) | 2228 (27.8) | 1993 (26.6) | 2024 (27.9) | 2294 (29.6) |  < 0.01 |