Figures
- FIGURE 1
The four stages of the analysis to test mediators of the association between socioeconomic circumstances (SECs) (parental education) and wheezing. a) Estimate unadjusted risk ratio by SECs, also adjusted for demographic factors, e.g. sex and ethnicity; b) explore association between SECs and hypothetical mediators; c) explore association between hypothetical mediators and wheezing; d) enter hypothetical mediators into model; mediation taken to be a reduction in relative risk ratio.
- FIGURE 2
Relative risk ratios (RRRs) for wheezing phenotypes comparing the lowest maternal education group to the highest in sequentially adjusted models. The final adjusted model includes maternal education + sex + ethnicity + maternal age at birth of child + maternal atopy + smoking in pregnancy + low birthweight (LBW) + preterm birth + Caesarean section + breastfeeding + postnatal environment (environmental tobacco smoke, “grime”, damp, pets, siblings and childcare). BMI: body mass index.
- FIGURE 3
Fully adjusted associations between covariates and wheezing phenotypes. GCSE: General Certificate of Secondary Education; BMI: body mass index; ETS: environmental tobacco smoke; RRR: relative risk ratio.
Tables
- TABLE 1
Characteristics of the total study population, by maternal qualifications
Total Degree plus Diploma A-levels GCSE grades A–C GCSE grades D–G None p-value# Subjects n (%) 11 141 (100) 1088 (17.8) 1165 (9.4) 1165 (9.8) 3861 (36.1) 1145 (11.2) 1722 (15.7) Wheeze phenotype Never 66.0 69.8 69.3 71.7 65.2 63.3 59.7 <0.001 Early remitting 17.1 15.7 14.2 13.1 17.6 19.6 19.9 Persistent/relapsing 12.0 11.5 11.6 11.0 12.1 12.9 12.9 Transient/intermittent 4.9 3.0 4.8 4.2 5.1 4.3 7.5 Female 49.1 49.9 47.3 49.8 48.4 48.6 48.6 0.95 Child's ethnicity White 88.0 88.9 90.5 89.7 92.2 91.4 72.5 <0.001 Mixed 3.0 3.7 2.8 2.7 2.6 2.7 3.7 Indian 1.7 2.4 1.4 2.4 0.9 1.2 2.7 Pakistani and Bangladeshi 3.8 1.2 1.2 3.0 2.3 2.6 13.1 Black or black British 2.5 2.5 3.4 1.3 1.6 1.9 5.3 Other 1.0 1.3 0.7 0.9 0.5 0.2 2.7 Maternal age years 14–19 7.5 0 0.5 3.9 8.0 16.7 14.8 <0.001 20–24 16.7 2.8 9.2 15.1 19.1 25.9 26.0 25–29 28.6 25.4 33.7 30.6 28.6 31.0 25.9 30–34 30.3 42.7 37.2 32.6 29.3 18.8 21.2 35–39 14.8 25.6 17.5 14.7 13.2 7.1 10.3 ≥40 2.1 3.5 1.9 3.1 1.8 0.6 1.8 Maternal atopy None 73.0 69.4 70.6 69.3 68.6 71.6 70.4 0.18 Asthma or eczema 23.4 21.4 25.0 21.6 24.6 23.9 22.4 Asthma and eczema 6.5 5.9 5.4 7.4 6.5 7.2 6.3 Maternal BMI Underweight 5.5 3.1 3.0 3.4 5.3 8.4 9.9 <0.001 Normal range 65.7 75.5 68.0 66.7 63.5 61.7 59.7 Overweight 20.1 15.5 20.6 20.5 21.3 19.5 22.5 Obese 6.3 5.0 5.9 6.3 7.3 7.2 5.4 Morbidly obese 2.4 0.9 2.6 3.0 2.6 3.2 2.5 Maternal smoking Never 65.2 87.8 77.6 76.0 60.3 47.7 48.8 <0.001 Smoked before pregnancy 14.7 9.4 14.6 14.2 18.4 17.2 10.5 Smoked during pregnancy 20.2 2.8 7.8 9.8 21.2 35.0 40.7 Low birthweight 6.2 3.6 5.3 5.3 6.2 6.4 10.0 <0.001 Caesarean section 20.5 24.8 24.1 19.1 20.1 18.4 16.9 <0.001 Preterm <37 weeks gestation 5.8 4.7 5.4 3.9 6.5 5.3 7.1 0.008 Breastfeeding Never 31.5 7.1 18.6 19.7 35.8 47.3 52.8 <0.001 ≤1 week 12.1 8.1 13.0 11.0 12.6 16.5 12.1 1–6 weeks 13.1 10.0 13.9 14.0 15.4 13.2 10.7 6 weeks–6 months 19.8 26.9 24.9 24.9 19.1 13.2 11.7 ≥6 months 23.6 47.9 29.7 30.5 17.0 9.8 12.7 Exposure to smoke in same room 13.1 2.9 4.4 6.8 13.2 23.0 26.2 <0.001 Damp exposure 13.5 9.8 9.7 11.4 13.0 16.0 20.6 <0.001 “Grime” in the environment 21.1 20.8 18.9 19.3 20.2 20.6 26.3 0.004 Furry pets 37.5 29.8 38.5 33.0 41.5 42.0 35.9 <0.001 Siblings in household n 1 49.5 44.6 45.1 41.5 45.8 31.6 42.2 2/3 51.1 47.2 51.9 51.3 53.1 48.6 51.8 <0.001 ≥4 6.9 3.3 3.3 3.8 6.2 6.4 17.2 Childcare None 68.2 49.0 59.1 60.5 70.9 76.8 87.9 <0.001 Informal 18.0 14.6 21.6 22.5 20.6 18.2 10.9 Formal 13.8 36.4 19.2 17.0 8.5 5.0 1.2 Data are presented as %, unless otherwise stated. All percentages are adjusted for sampling design and attrition. Item missingness: ethnicity 23, maternal age 7, maternal atopy 17, maternal body mass index (BMI) 657, maternal smoking 36, preterm birth 155, Caesarean section 9, environmental tobacco smoke exposure 1, damp exposure 16, grime exposure 103, furry pet exposure 1, childcare type 42. GCSE: General Certificate of Secondary Education. #: Chi-squared.
- TABLE 2
Prevalence of wheeze patterns by covariates and univariate relative risk ratios (RRRs) for wheeze patterns for each covariate
Never Early remitting Persistent/relapsing % RRR (95% CI) % RRR (95% CI) % RRR (95% CI) Total 66 17.1 12.0 Maternal qualifications Degree plus 69.8 1 15.7 1.00 (1.00–1.00) 11.5 1.00 (1.00–1.00) Diploma 69.3 1 14.2 0.91 (0.72–1.15) 11.6 1.02 (0.77–1.35) A-levels 71.7 1 13.1 0.81 (0.66–1.00) 11 0.93 (0.72–1.20) GCSE grades A–C 65.2 1 17.6 1.20 (1.02–1.41) 12.1 1.12 (0.92–1.37) GCSE grades D–G 63.3 1 19.6 1.37 (1.10–1.71) 12.9 1.24 (0.94–1.63) None 59.7 1 19.9 1.48 (1.22–1.80) 12.9 1.31 (1.04–1.65) Demographic factors Male 62.9 1 17.6 1.00 (1.00–1.00) 14.2 1.00 (1.00–1.00) Female 69.6 1 16.4 0.84 (0.75–0.94) 9.7 0.61 (0.53–0.71) Ethnicity White 66.1 1 17.1 1.00 (1.00–1.00) 12 1.00 (1.00–1.00) Mixed 63.3 1 18.7 1.14 (0.80–1.63) 11.9 1.03 (0.72–1.49) Indian 69.4 1 12.4 0.69 (0.45–1.06) 13.1 1.04 (0.62–1.73) Pakistani and Bangladeshi 66.6 1 14.4 0.84 (0.68–1.03) 12.8 1.06 (0.79–1.41) Black or black British 62.9 1 21.1 1.30 (0.92–1.84) 10.5 0.92 (0.61–1.38) Other 78 1 9 0.45 (0.28–0.72) 8.6 0.60 (0.32–1.14) Maternal age years 14–19 60.7 1 22.9 1.82 (1.40–2.37) 10.7 0.90 (0.65–1.25) 20–24 63.2 1 19.4 1.48 (1.21–1.81) 12.1 0.98 (0.77–1.25) 25–29 66.1 1 17.1 1.25 (1.03–1.50) 11.8 0.91 (0.74–1.13) 30–34 68.6 1 15.2 1.07 (0.90–1.28) 11.9 0.89 (0.74–1.07) 35–39 67.9 1 14.1 1.00 (1.00–1.00) 13.3 1.00 (1.00–1.00) ≥40 62.5 1 20.7 1.60 (1.12–2.28) 10.9 0.89 (0.57–1.41) Maternal atopy No risk 69.5 1 15.6 1.00 (1.00–1.00) 10.1 1.00 (1.00–1.00) Asthma or eczema/hayfever 59.7 1 19.7 1.47 (1.28–1.67) 15.4 1.76 (1.53–2.03) Asthma and eczema/hayfever 52.9 1 21.9 1.84 (1.46–2.33) 19.8 2.57 (2.03–3.25) Maternal BMI Underweight 65 1 19.9 1.26 (0.95–1.67) 11.9 1.10 (0.79–1.52) Normal range 67.4 1 16.4 1.00 (1.00–1.00) 11.2 1.00 (1.00–1.00) Overweight 63.9 1 17.5 1.13 (0.97–1.31) 13.3 1.25 (1.05–1.48) Obese 63.6 1 18.4 1.19 (0.97–1.47) 14.6 1.38 (1.06–1.80) Morbidly obese 57.6 1 22.2 1.58 (1.10–2.29) 15.1 1.57 (1.01–2.45) Maternal smoking Never 69.4 1 15.1 1.00 (1.00–1.00) 11.2 1.00 (1.00–1.00) Smoked before pregnancy 62.7 1 18.6 1.36 (1.16–1.61) 12.8 1.26 (1.06–1.50) Smoked during pregnancy 58.3 1 22.2 1.75 (1.51–2.03) 13.6 1.44 (1.23–1.69) Cigarettes smoked during pregnancy cigarettes·day-1 0 68.2 1 15.7 1.00 (1.00–1.00) 11.5 1.00 (1.00–1.00) 1–9 61.5 1 21.1 1.49 (1.23–1.80) 11.8 1.13 (0.91–1.41) 10–19 57.9 1 21.7 1.63 (1.33–1.99) 14.7 1.50 (1.17–1.93) ≥20 54.5 1 21.8 1.74 (1.24–2.42) 16.3 1.77 (1.26–2.48) Perinatal factors Low birthweight# 59.2 1 19.5 1.30 (1.03–1.65) 16.4 1.58 (1.18–2.10) Caesarean section# 63.6 1 17.3 1.08 (0.94–1.25) 14 1.29 (1.08–1.53) Preterm <37 weeks gestation# 54.2 1 22.3 1.64 (1.29–2.09) 16.9 1.77 (1.34–2.35) Breastfeeding Never 61.8 1 19.7 1.00 (1.00–1.00) 13.2 1.00 (1.00–1.00) ≤1 week 64.5 1 18.2 0.88 (0.73–1.08) 12.3 0.89 (0.72–1.11) 1–6 weeks 66.9 1 16.5 0.88 (0.73–1.07) 11.3 0.97 (0.78–1.20) 6 weeks–6 months 71 1 13.8 0.71 (0.60–0.84) 11.3 0.72 (0.59–0.87) Postnatal exposures Environmental tobacco smoke# 62.3 1 19.5 1.26 (1.07–1.48) 13 1.17 (0.96–1.44) Damp# 62.6 1 19.1 1.22 (1.02–1.46) 12.5 1.12 (0.93–1.35) Grime# 63.3 1 18.5 1.19 (1.03–1.37) 12.8 1.15 (0.99–1.33) Pets# 66.3 1 16.9 0.99 (0.89–1.11) 11.3 0.90 (0.79–1.04) Siblings in household n 1 66.5 1 16.4 1.00 (1.00–1.00) 11.9 1.00 (1.00–1.00) 2/3 65.8 1 17.9 1.10 (0.98–1.24) 11.8 1.00 (0.89–1.12) ≥4 66.5 1 13.9 0.85 (0.66–1.09) 14.4 1.21 (0.93–1.56) Childcare No 65.8 1 16.5 1.00 (1.00–1.00) 5.3 1.00 (1.00–1.00) Informal 66.3 1 17.7 1.06 (0.91–1.24) 4.4 0.94 (0.79–1.12) Formal 67.6 1 18.3 1.08 (0.93–1.24) 3.5 0.84 (0.68–1.04) Data are presented as % or RRR (95% CI). n=11 141. GCSE: General Certificate of Secondary Education; BMI: body mass index. #: reference group for binary variables not shown; reference not low birthweight/Caesarean section/preterm birth.
Disclosures
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