Introduction
Methods
Study design
Definition of ethnicity
Outcomes
Mediators and confounders
-
Socioeconomic status (SES) defined by net monthly income of the household (<900, 900–2,200 or >2,200 Euro), maternal education (low, intermediate or high vocational training) and marital status (married/living together or living alone).
-
Prenatal environment and perinatal characteristics. Prenatal smoke exposure by the mother and parental atopy were assessed by questionnaire; birth weight (kg) and gestational age (weeks) were obtained from hospital registries.
-
Postnatal environment and nutrition. Based on the answer to pre-and postnatal questionnaires, the variable ‘pets keeping’ was grouped in 4 mutually exclusive categories (never exposed, prenatal exposure only, postnatal exposure only or pre and postnatal exposure). Breastfeeding and the number of siblings in the household were recorded at 6 months. Daycare attendance in the past 12 months was investigated at 12 and at 24 months. Postnatal environmental tobacco smoke exposure was assessed at 24 months.
-
Previous morbidity. At 12 and 24 months doctor-diagnosed child allergy, upper respiratory symptoms (URS), eczema, respiratory and non-respiratory tract infections were assessed.
-
Gender and age of the child at the time of completion of the 12 and 24 months’ questionnaires were included in all regression models as confounders.
Statistical analysis
Results
Study population
Dutch (N = 3,217) | Cape Verdean (N = 163) | Moroccan (N = 350) | Antillean (N = 178) | Surinamese (N = 400) | Turkish (N = 434) | Others (N = 942) | |
---|---|---|---|---|---|---|---|
Male gender | 50 % | 49 % | 49 % | 60 %†
| 46 % | 47 % | 51 % |
Educational level mother* | |||||||
High | 59 % | 13 % | 14 % | 19 % | 19 % | 14 % | 56 % |
Intermediate | 38 % | 63 % | 59 % | 67 % | 68 % | 51 % | 34 % |
Low | 3 % | 24 % | 27 % | 14 % | 13 % | 35 % | 10 % |
Monthly family net income* | |||||||
>2,200 Euro | 75 % | 11 % | 11 % | 20 % | 33 % | 14 % | 53 % |
900–2,200 Euro | 21 % | 51 % | 68 % | 40 % | 45 % | 62 % | 35 % |
<900 Euro | 4 % | 38 % | 21 % | 40 % | 22 % | 23 % | 12 % |
Mother married/living together | 92 % | 58 %‡
| 91 % | 46 %‡
| 66 %‡
| 95 % | 85 %‡
|
Prenatal maternal smoking | 24 % | 22 % | 7 %‡
| 31 %†
| 29 %†
| 35 %‡
| 20 %‡
|
Maternal atopy | 39 % | 35 % | 37 % | 46 % | 36 % | 33 %†
| 35 %†
|
Birth weight: mean (SD) g | 3.485 (0.5)§
| 3.303 (0.5) | 3.523 (0.5) | 3.174 (0.6) | 3.184 (0.6) | 3.387 (0.5) | 3.383 (0.5) |
Gestational age: mean (SD) weeks | 40.0 (1.7)§
| 39.9 (1.4) | 40.3 (1.5) | 39.5 (1.8) | 39.5 (1.8) | 39.9 (1.8) | 39.9 (1.7) |
Pets keeping* | 55 % | 80 % | 92 % | 77 % | 75 % | 85 % | 72 % |
Never | 7 % | 8 % | 4 % | 7 % | 9 % | 7 % | 5 % |
Only prenatal | 6 % | 7 % | 1 % | 4 % | 5 % | 3 % | 4 % |
Only postnatal | 32 % | 5 % | 3 % | 12 % | 11 % | 5 % | 19 % |
Pre and postnatal | |||||||
Breastfeeding | 28 % | 19 %†
| 27 % | 15 %‡
| 19 %‡
| 40 %‡
| 39 %‡
|
Siblings | 34 % | 50 %‡
| 57 %‡
| 34 % | 40 %†
| 51 %‡
| 33 % |
Daycare attendance at 0–12 months | 92 % | 87 % | 66 %‡
| 79 %‡
| 85 %‡
| 59 %‡
| 82 %‡
|
Daycare attendance at 12–24 months | 89 % | 88 % | 51 %‡
| 82 %†
| 81 %‡
| 48 %‡
| 78 %‡
|
Postnatal smoke exposure | 30 % | 25 % | 24 % | 40 %†
| 42 %‡
| 56 %‡
| 30 % |
Child allergy | 6 % | 6 % | 7 % | 8 % | 6 % | 3 % | 7 % |
URS at 0–12 months | 38 % | 50 % | 46 %†
| 40 % | 50 %‡
| 44 % | 43 %†
|
URS at 12–24 months | 30 % | 39 % | 31 % | 36 % | 35 % | 37 %†
| 28 % |
Eczema at 0–12 months | 31 % | 34 % | 48 %‡
| 37 % | 48 %‡
| 36 % | 35 % |
Eczema at 12–24 months | 22 % | 27 % | 16 % | 30 % | 31 %‡
| 14 %‡
| 22 % |
Infections at 0–12 months | |||||||
No | 18 % | 23 % | 20 % | 19 % | 20 % | 14 % | 20 % |
URTI or LRTI | 68 % | 63 % | 76 % | 76 % | 70 % | 84 % | 68 % |
Other infections | 14 % | 14 % | 4 % | 5 % | 10 % | 2 % | 12 % |
Infections at 12–24 months* | |||||||
No | 10 % | 5 % | 11 % | 6 % | 11 % | 5 % | 10 % |
URTI or LRTI | 71 % | 86 % | 78 % | 85 % | 78 % | 89 % | 75 % |
Other infections | 19 % | 9 % | 11 % | 9 % | 11 % | 6 % | 15 % |
Dutch (N = 3,217) | Cape Verdean (N = 163) | Moroccan (N = 350) | Antillean (N = 178) | Surinamese (N = 400) | Turkish (N = 434) | Others (N = 942) | |
---|---|---|---|---|---|---|---|
Wheezing | |||||||
No | 59 % | 30 % | 35 % | 39 % | 4 %3 | 40 % | 54 % |
Yes | 26 % | 17 % | 10 % | 18 % | 15 % | 20 % | 17 % |
Missing | 15 % | 53 % | 55 % | 43 % | 41 % | 40 % | 29 % |
Breathlessness | |||||||
No | 64 % | 41 % | 37 % | 45 % | 49 % | 50 % | 59 % |
Yes | 21 % | 7 % | 8 % | 12 % | 9 % | 10 % | 12 % |
Missing | 15 % | 52 % | 55 % | 43 % | 42 % | 40 % | 29 % |
Dry cough without a cold | |||||||
No | 64 % | 39 % | 36 % | 44 % | 47 % | 46 % | 55 % |
Yes | 20 % | 8 % | 10 % | 11 % | 11 % | 13 % | 15 % |
Missing | 16 % | 53 % | 54 % | 45 % | 42 % | 41 % | 30 % |
Persistent phlegm | |||||||
No | 75 % | 36 % | 36 % | 41 % | 49 % | 44 % | 59 % |
Yes | 9 % | 10 % | 10 % | 15 % | 10 % | 14 % | 10 % |
Missing | 16 % | 54 % | 54 % | 44 % | 41 % | 14 % | 31 % |
Doctor-diagnosed asthma | |||||||
No | 82 % | 45 % | 43 % | 53 % | 56 % | 56 % | 67 % |
Yes | 2 % | 1 % | 2 % | 4 % | 2 % | 2 % | 3 % |
Missing | 16 % | 53 % | 55 % | 43 % | 42 % | 42 % | 30 % |
LRS at 0–12 months | |||||||
No | 41 % | 23 % | 28 % | 24 % | 31 % | 26 % | 40 % |
Yes | 45 % | 25 % | 18 % | 33 % | 28 % | 34 % | 31 % |
Missing | 14 % | 52 % | 54 % | 43 % | 41 % | 40 % | 29 % |
Dutch (N = 3,217) | Cape Verdean (N = 163) | Moroccan (N = 350) | Antillean (N = 178) | Surinamese (N = 400) | Turkish (N = 434) | Others (N = 942) | |
---|---|---|---|---|---|---|---|
Wheezing | |||||||
No | 68 % | 40 % | 41 % | 34 % | 45 % | 46 % | 59 % |
Yes | 16 % | 12 % | 7 % | 14 % | 14 % | 14 % | 13 % |
Missing | 16 % | 48 % | 52 % | 52 % | 41 % | 40 % | 28 % |
Breathlessness | |||||||
No | 68 % | 43 % | 43 % | 36 % | 52 % | 53 % | 62 % |
Yes | 16 % | 9 % | 6 % | 12 % | 7 % | 7 % | 10 % |
Missing | 16 % | 48 % | 51 % | 52 % | 41 % | 40 % | 28 % |
Dry cough without a cold | |||||||
No | 64 % | 37 % | 40 % | 34 % | 47 % | 43 % | 56 % |
Yes | 20 % | 13 % | 9 % | 15 % | 13 % | 20 % | 16 % |
Missing | 16 % | 50 % | 51 % | 51 % | 40 % | 37 % | 28 % |
Persistent phlegm | |||||||
No | 77 % | 38 % | 45 % | 39 % | 50 % | 51 % | 65 % |
Yes | 7 % | 14 % | 3 % | 10 % | 9 % | 12 % | 7 % |
Missing | 16 % | 48 % | 51 % | 51 % | 41 % | 37 % | 28 % |
Doctor-diagnosed asthma | |||||||
No | 82 % | 49 % | 48 % | 46 % | 57 % | 60 % | 71 % |
Yes | 2 % | 3 % | 1 % | 2 % | 3 % | 2 % | 2 % |
Missing | 16 % | 48 % | 51 % | 52 % | 40 % | 38 % | 27 % |
LRS at 12–24 months | |||||||
No | 47 % | 28 % | 32 % | 21 % | 33 % | 30 % | 43 % |
Yes | 38 % | 25 % | 16 % | 28 % | 26 % | 33 % | 30 % |
Missing | 15 % | 47 % | 52 % | 51 % | 41 % | 37 % | 27 % |
Ethnicity and lower respiratory symptoms
Basic model | Model ‘SES’ | Model ‘Prenatal’ | Model ‘Postnatal’ | Model ‘Morbidity’ | |
---|---|---|---|---|---|
Ethnicity | |||||
Dutch | Reference | Reference | Reference | Reference | Reference |
Cape Verdean | 1.07 (0.88–1.32) | 1.07 (0.88–1.32) | 1.08 (0.88–1.33) | 1.02 (0.85–1.25) | 1.06 (0.87–1.29) |
Moroccan | 0.95 (0.81–1.12) | 0.99 (0.84–1.18) | 1.01 (0.85–1.19) | 1.01 (0.87–1.18) | 0.92 (0.80–1.07) |
Antillean | 1.12 (0.89–1.41) | 1.11 (0.89–1.38) | 1.10 (0.88–1.38) | 1.09 (0.88–1.35) | 1.09 (0.94–1.26) |
Surinamese | 0.95 (0.82–1.10) | 0.96 (0.83–1.11) | 0.96 (0.83–1.12) | 0.95 (0.81–1.12) | 0.91 (0.80–1.04) |
Turkish | 1.14 (1.02–1.27) | 1.19 (1.06–1.34) | 1.19 (1.06–1.33) | 1.21 (1.06–1.37) | 1.20 (1.07–1.35) |
Others | 0.89 (0.83–0.96) | 0.89 (0.82–0.97) | 0.90 (0.83–0.97) | 0.92 (0.85–0.99) | 0.92 (0.84–0.99) |
Basic model | Model ‘SES’ | Model ‘Prenatal’ | Model ‘Postnatal’ | Model ‘Morbidity’ | |
---|---|---|---|---|---|
Ethnicity | |||||
Dutch | Reference | Reference | Reference | Reference | Reference |
Cape Verdean | 1.18 (0.92–1.51) | 1.09 (0.84–1.42) | 1.11 (0.85–1.45) | 1.05 (0.80–1.39) | 0.95 (0.79–1.16) |
Moroccan | 0.92 (0.75–1.12) | 0.91 (0.74–1.12) | 0.93 (0.76–1.15) | 0.95 (0.78–1.15) | 0.88 (0.73–1.06) |
Antillean | 1.32 (1.12–1.57) | 1.21 (1.02–1.43) | 1.21 (1.01–1.44) | 1.16 (0.96–1.40) | 1.07 (0.92–1.25) |
Surinamese | 1.04 (0.91–1.18) | 0.99 (0.86–1.13) | 0.99 (0.87–1.14) | 0.97 (0.84–1.11) | 0.97 (0.85–1.10) |
Turkish | 1.21 (1.07–1.38) | 1.21 (1.05–1.40) | 1.22 (1.05–1.41) | 1.22 (1.05–1.42) | 1.06 (0.96–1.17) |
Others | 0.94 (0.85–1.05) | 0.93 (0.83–1.04) | 0.94 (0.84–1.04) | 0.94 (0.85–1.05) | 0.98 (0.90–1.06) |