Table 1.

Sample composition

	Childhood-onset asthma	Adult-onset asthma	Controls
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

^aHours/week among non-smokers

SD standard deviation