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Table 1 Characteristics of the 45,555 pre-adolescents included in the study population according to the main exposure status (screen-based activity) (11-year follow-up, The Danish National Birth Cohort, 1996–2003)

From: Spinal pain in pre-adolescence and the relation with screen time and physical activity behavior

   Average time spent on screen-based activity (h/day)a
Characteristics N <  2 2 to < 4 4 to < 6 ≥ 6
Totalb 45,555 (100) 10,104 (22.2) 22,057 (48.4) 9452 (20.8) 3942 (8.7)
Physical activity behavior      
 Inactive 5201 (11.4) 753 (7.5) 2251 (10.2) 1366 (14.5) 831 (21.6)
 Lightly active 20,436 (44.9) 4186 (41.5) 9730 (44.1) 4544 (48.1) 1973 (49.3)
 Moderately active 17,853 (39.2) 4519 (44.7) 9065 (41.1) 3218 (34.1) 1051 (26.7)
 Vigorously active 2065 (4.5) 643 (6.4) 1011 (4.6) 324 (3.4) 87 (2.2)
Sex      
 Boys 21,711 (47.7) 3686 (36.5) 10,177 (46.1) 5355 (56.7) 2493 (63.2)
 Girls 23,844 (52.3) 6418 (63.5) 11,880 (53.9) 4097 (43.4) 1449 (36.8)
Age      
 11 years 38,326 (84.1) 8943 (88.5) 18,784 (85.2) 7599 (80.4) 3000 (76.1)
 12 years 7229 (15.9) 1161 (11.5) 3273 (14.8) 1853 (19.6) 942 (23.9)
Parental educational levelc      
 High 30,629 (67.2) 7389 (73.1) 14,994 (68.10) 5987 (63.3) 2259 (57.3)
 Medium 14,100 (31.0) 2579 (25.5) 6699 (30.4) 3276 (34.7) 1546 (39.2)
 Low 826 (1.8) 136 (1.4) 364 (1.7) 189 (2.0) 137 (3.5)
Equivalised household incomec      
 4th quartile (highest) 16,333 (35.9) 4082 (40.4) 8095 (36.7) 3055 (32.3) 1101 (27.9)
 3rd quartile 14,011 (30.8) 2996 (29.7) 6848 (31.1) 3010 (31.9) 1157 (29.4)
 2nd quartile 10,225 (22.4) 2006 (19.9) 4836 (22.0) 2259 (23.9) 1124 (28.5)
 1st quartile (lowest) 4986 (11.0) 1020 (10.1) 2278 (10.3) 1128 (12.0) 560 (14.2)
Family type      
 Living with both parents 35,638 (78.2) 8110 (80.3) 17,449 (79.1) 7193 (76.1) 2886 (73.2)
 Not living with (both) parentsd 9917 (21.8) 1994 (19.7) 4608 (20.9) 2259 (23.9) 1056 (26.8)
Paritye      
 Nulliparous 21,976 (48.2) 5498 (54.4) 10,755 (48.6) 4152 (43.9) 1571 (39.9)
 Parous 23,579 (51.8) 4606 (45.6) 11,302 (51.4) 5300 (56.1) 2371 (60.2)
  1. a Variables were analyzed with the chi-squared test of heterogeneity. Chi-squared tests were statistically significant for all variables
  2. b For total distribution of screen-based activity row percentage is shown; for all the covariates column percentages are shown
  3. c Measured the year of the child’s 11th birthday
  4. d Parents not living together due to divorce, separation, they never lived together or only one parent alive
  5. e Maternal parity status in index pregnancy