Table 1 Characterization of sample by sex: middle school cohort, ELANA study, 2010 and (2012)

 Age (CI 95 %)

11.2 (11.0–11.3)

11.0 (10.9–11.1)

0.037 ^a

 Pre-pubescent

5.8

6.4

<0.001 ^b

 Early spurt

73.1

28.9

 Maximum speed peak

16.3

47.0

 Slowing growth

4.4

17.7

 Public

30.7

30.9

0.953^b

 Private

69.3

69.1

 Less asset ownership

25.3

12.7

<0.001 ^b

 More asset ownership

74.7

87.3

 Mean (CI 95 %)

20.6 (20.1–21.2)

20.2 (19.7–20.7)

0.265^a

 Normal (%)

82.4

87.8

 Overweight/obesity (%)

17.6

12.2

0.090^b

 Mean (CI 95 %)

66.0(58.7–73.3)

43.9(38.4–49.5)

<0.001^a

  > 60 min/day^c (%)

36.5

22.5

  ≤ 60 min/day ((%)

63.5

77.5

<0.001 ^b

 Mean (CI 95 %)

320.9 (293.6–348.2)

301.1(271.1–331.1)

0.337^a

  ≤ 4 h/day^c (%)

48.0

53.6

  > 4 h/day (%)

52.0

46.4

0.199^b

 Mean (CI 95 %)

49.5 (47.5–50.1)

50.2(48.8–51.4)

0.405^a

 Poor (%)

12.3

13.3

 Good (%)^c

87.7

86.7

0.737^b

 Mean (CI 95 %)

42.1(37.2–46.9)

29.5(24.7–34.3)

<0.001 ^a

  > 60 min/day^c (%)

26.0

13.3

  ≤ 60 min/day ((%)

74.0

86.7

<0.001 ^b

 Mean (CI 95 %)

355.5(326.3–384.7)^d

381.1(348.9–413.3)^d

0.245^a

  ≤ 4 h/day^c (%)

43.7

39.8

  > 4 h/day (%)

56.3

60.2

0.362^b