Table 1

Characteristics of the population, comparison of subjects with and without missing data on any of the outcome variables

Outcomes data complete, n = 551 n (%)Missing outcomes data, n = 91 n (%)p value†
n, number of observations.
*Mean (standard deviation).
†p from χ2 test for categorical variables and from two-sample t test for continuous variables.
Male gender (n = 641)294 (53.4)49 (54.4)0.85
Parental asthma (n = 638)137 (25.0)25 (27.8)0.58
Parental atopy (n = 576)320 (63.0)46 (67.7)0.45
Smoking in household at age 5½ (n = 604)198 (35.9)22 (41.5)0.42
Mother’s further education (n = 613)280 (51.2)36 (54.6)0.61
Maternal age at birth (n = 640)27.7 (4.8)*27.5 (5.0)*0.69
Birth weight in grams (n = 639)3407.0 (566.5)*3252.9 (575.7)*0.02
Birth order (n = 642)0.67
    First233 (42.3)37 (40.7)
    Second199 (36.1)37 (40.7)
    Third to sixth119 (21.6)17 (18.7)
First feeding of solids after 3rd month (n = 593)234 (44.6)33 (48.5)0.54
Ever breast fed (n = 623)347 (63.0)41 (56.9)0.32