Table 1– Potential risk factors considered for fitting the predictive models
Risk factorsTotal participants#Missing dataImputed
Subjects n1570
Subjects in SOLAR II aged ≤21 years+552 (35.2)0No
Female918 (58.5)0No
Study location Munich758 (48.3)0No
Nationality German1518 (96.7)5 (0.3)Yes
High socioeconomic status§921 (58.7)21 (1.3)Yes
Exposure to environmental tobacco smoke25 (1.6)Yes
 ISAAC phase II: current exposure439 (28.0)
 ISAAC phase II: former exposure135 (8.6)
 SOLAR I960 (61.2)6 (0.4)Yes
Ever smokersƒ as indicated in SOLAR I480 (30.6)12 (0.8)Yes
Having been breastfed1348 (85.9)12 (0.8)Yes
Kindergarten attendance1550 (98.7)10 (0.6)Yes
Presence of siblings1273 (81.1)13 (0.8)Yes
Parental history of
 Allergic rhinitis595 (37.9)138 (8.8)Yes
 Asthma166 (10.6)127 (8.1)Yes
 Atopic dermatitis304 (19.4)157 (10.0)Yes
Positive skin prick test response in ISAAC phase II320 (23.7)221 (14.1)No
Occupational exposure166 (10.6)Yes##
 No risk624 (39.7)
 Low risk383 (24.4)
 High risk563 (35.9)
  • Data are presented as n (%), unless otherwise stated. SOLAR: Study on Occupational Allergy Risks; ISAAC: International Study of Asthma and Allergies in Childhood. #: frequencies displayed for one random imputed data set; : frequencies of missing values before imputation; +: age was dichotomised in two groups of comparable range (19–21 years and 22–24 years); §: mother or father qualified for university entrance or university diploma; ƒ: ≥1 pack-year, never-smoker defined as <1 pack-year until SOLAR I; ##: only missing time values were imputed to assess relevance of job regarding duration and intensity of potential occupational exposure; jobs lasting ≥4 weeks with ≥8 working hours per week were deemed relevant.