Table 1 Sample composition

Sample size

9432

21,554

318,167

Mean age of asthma onset in years (SD)

6 (3)

44 (10)

NA

Any asthma medication use (%)

41.6

44.8

0.5

Female sex (%)

40.7

63.6

53.5

Allergic disease (ever, %)

34.0

24.6

10.6

Allergic rhinitis (%)

26.9

21.6

8.6

Atopic dermatitis (%)

11.9

4.3

2.3

Food allergy (%)

1.5

0.8

0.4

Mean FEV1 percent predicted (SD)

87.62 (18.20)

91.80 (17.05)

98.41 (15.62)

Mean FEV1/FVC (SD)

0.71 (0.08)

0.74 (0.07)

0.76 (0.06)

Mean eosinophil count (SD)

0.23 (0.18)

0.22 (0.17)

0.17 (0.12)

Mean tobacco exposure in home (SD)^a

0.58 (4.89)

0.62 (4.93)

0.51 (4.35)

Current tobacco smoking (% never/occasionally/most days)

91.4/ 6.0/ 2.6

93.5/ 4.7/ 1.8

90.4/ 7.0/ 2.6