Table 2

Percentage distribution of values of each factor in each group of children, with chi-square tests of association

% of each group of children

Chi2 (df), with p value below


All asthma

(N = 4017)

Asthma, aged 0-1

(N = 535)

Asthma, aged 2+

(N = 3482)

No asthma

(N = 244595)

All asthma

Asthma aged 0-1

Asthma aged 2+


Maternal asthma:


No

92.0

91.0

92.2

97.6

495.6(1)

96.2(1)

409.1(1)


Yes

8.0

9.0

7.8

2.4

0.0001

<0.0001

0.0001


Total

100

100

100

100


Year of birth:


1970-1974

18.9

4.1

21.1

27.9

200.4(3)

497.9 (3)

94.1(3)


1975-1979

21.7

7.7

23.8

22.7

<0.0001

<0.0001

0.0001


1980-1984

28.4

23.2

29.2

24.2


1985-1989

31.0

65.0

25.8

25.2


Total

100

100

100

100



Maternal age:


14-24

37.3

38.5

37.1

34.8

11.8(2)

4.0 (2)

10.2(2)


25-34

55.0

55.3

54.9

57.6

0.003

0.14

0.006


35-49

7.7

6.2

8.0

7.6


Total

100

100

100

100



Social class:


I + II

30.2

29.7

30.2

35.9

48.6(2)

7.4(2)

41.5(2)


III

48.2

48.1

48.2

45.5

<0.0001

0.025

0.0001


IV + V

21.6

22.2

21.6

18.6


Total

100

100

100

100



Marital status:


Married

88.0

79.4

89.4

90.4

25.3(1)

74.0(1)

4.3(1)


Not married

12.0

20.6

10.6

9.6

<0.0001

0.0001

0.04


Total

100

100

100

100



Parity of mother:


0

40.5

35.5

41.2

42.0

14.0(4)

24.2(4)

4.65(4)


1

35.4

35.3

35.3

35.9

0.007

<0.0001

0.33


2

15.3

16.8

15.1

14.5


3

5.9

8.6

5.5

4.9


4+

2.9

3.6

2.9

2.7


Total

100

100

100

100



Maternal smoking:


No

71.7

63.3

73.4

76.5

34.9(1)

46.0(1)

11.7(1)


Yes

28.3

36.7

26.6

23.5

0.0001

0.0001

0.0006


Total

100

100

100

100



Gestational age (wks):


24-37

12.8

18.0

12.1

10.1

43.2(3)

33.2 (2)

13.3(2)


38-41

77.4

70.7

78.3

80.4

0.0001

0.0001

0.001


42-47

9.8

11.3

9.6

9.5


Total

100

100

100

100



Birth weight:


1000-2999

27.1

32.0

26.3

23.6

27.4(2)

22.5 (2)

16.1(2)


3000-3999

64.4

61.8

64.8

67.9

0.0001

0.0001

0.0003


4000-5499

8.5

6.2

8.9

8.5


Total

100

100

100

100



Caesarean delivery:


No

91.0

89.8

91.2

92.6

14.1(1)

5.7(1)

9.7(1)


Yes

9.0

10.2

8.8

7.4

0.0002

0.02

0.002


Total

100

100

100

100



Forceps delivery:


No

88.2

93.4

87.4

86.9

5.9(1)

18.5(1)

1.0(1)


Yes

11.8

6.6

12.6

13.1

0.01

0.0001

0.33


Total

100

100

100

100



Apgar 1:


1-5

8.4

9.3

8.2

9.5

9.4(2)

2.1(2)

8.5(2)


6-8

30.3

31.3

30.2

28.48

0.01

0.35

0.01


9-10

96.1

59.4

61.6

62.5


Total

100

100

100

100



Number of babies in birth delivery:


Singleton

98.1

97.6

98.2

97.8

1.7(1)

0.2(1)

2.9(1)


Multiple birth

1.9

2.4

1.8

2.2

0.19

0.68

0.09


Total

100

100

100

100



Sex of baby:


Female

32.4

30.1

38.5

48.8

205.9(1)

74.6(1)

145.5


Male

67.4

69.9

61.5

51.2

<0.0001

0.0001

0.0001


Total

100

100

100

100



Breastfed or not:


Not breastfed

32.6

41.6

30.9

30.2

8.1(1)

29.7(1)

0.6(1)


Breastfed

67.4

58.4

69.1

69.8

0.004

0.0001

0.46


Total

100

100

100

100


Missing values: maternal asthma none missing; year of birth none; mother's age 7 (0.2% of cases; social class 869 (27.6%*); marital status 8 (0.2%); parity 2 (0.05%); maternal smoking 1278 (31.8%*); gestational age 558 (13.9%); birth weight 114 (2.8%); caesarean section 114 (2.8%); forceps 114 (2.8%); Apgar 1 1164 (29.0%*); number of babies none missing; sex none; breastfeeding 961 (23.9%*). * = data item not collected in the first five years covered by the study. Numbers on which the percentages are based are given in additional files (see Additional file 1).

Davidson et al. BMC Pulmonary Medicine 2010 10:14   doi:10.1186/1471-2466-10-14

Open Data