Figures
- Fig. 1—
A map illustrating the results from the dispersion model for Umeå in 50-m squares. Darker colours indicate higher winter mean levels of nitrogen dioxide.
Tables
- Table 1—
Characteristics of cases and noncases from the population at risk
Onset asthma Incident asthma Cases Noncases p-value Cases Noncases p-value Total n 116 3708 58 3766 Males n 41 1739 18 1762 Females n 75 1969 0.01¶ 40 2004 0.02 BMI mean kg·m2 25.4 24.7 0.06+ 25.3 24.7 0.26+ Age in 1999 mean yrs 39.4 39.7 0.61+ 39.7 39.7 0.97+ Smoking % never/former/current 46/29/25 51/25/24 0.50§ 41/32/27 51/25/24 0.32§ Hay fever % 48.7 18.6 <0.00§ 40.4 19.2 <0.00§ Water/mould# % 24.3 23.2 0.74§ 20.7 23.3 0.76§ The table includes those who received a modelled value of nitrogen dioxide and could be classified as cases or noncases according to the definition of onset and incident asthma. BMI: body mass index. #: water damage or mould in the home at any time during the last 8 yrs; ¶: Pearson’s Chi-squared test comparing the proportional difference of males and females among cases; +: unpaired t-test comparing cases with asthma with those without asthma; §: Pearson’s Chi-squared test comparing cases with asthma with those without asthma.
- Table 2—
Descriptive information on the modelled winter average levels of nitrogen dioxide for cities and for onset and incident cases and noncases
Mean±sd Percentiles Minimum Maximum p-value# 25th 50th 75th Total 17.9±6.4 12.9 17.2 21.9 3.3 45.6 Gothenburg 19.1±6.8 13.1 18.3 24.4 3.3 45.6 Umeå 18.9±5.8 15.0 18.5 22.4 7.9 41.4 Uppsala 14.6±4.7 10.8 14.7 17.8 5.4 28.7 Onset asthma Noncases 17.9±6.4 12.9 17.1 21.8 3.3 45.0 0.03 Cases 19.2±7.1 13.7 17.8 24.0 6.8 45.6 Incident asthma Noncases 17.9±6.4 12.9 17.1 21.8 3.3 45.6 0.12 Cases 19.2±6.1 15.6 18.2 24.1 6.8 33.7 Distance to major road <50 m Onset cases 25.1±7.8 21.7 23.2 29.4 12.7 45.6 Onset noncases 24.1±6.8 19.8 23.1 27.3 9.6 44.6 Incident cases 24.3±6.0 21.1 24.4 29.1 12.7 32.7 Incident noncases 24.1±6.9 20.0 23.1 27.3 9.6 45.6 Data are given in μg·m−3 as winter half-yr concentrations, unless otherwise stated. #: unpaired t-test comparing the mean value for cases and noncases.
- Table 3—
The number of cases and noncases for two definitions of asthma in relation to the distance to the nearest major road
Distance to major road# Onset asthma Incident asthma Cases Noncases Cases Noncases ≥50 m 129 4370 58 4441 <50 m 17 220 10 227 #: ≥8,000 vehicles per 24 h.
- Table 4—
Associations between exposures to nitrogen dioxide(NO2), distance to nearest major road and the onset and incidence of asthma
Onset asthma Incident asthma OR 95% CI OR 95% CI Crude# NO2 per 10 μg·m−3 1.39 1.05–1.84 1.36 0.92–2.02 Distance to nearest major road <50 m¶ 2.81 1.66–4.76 3.55 1.78–7.01 Fully adjusted+ NO2 per 10 μg·m−3 1.46 1.07–1.99 1.54 1.00–2.36 Distance to nearest major road <50 m¶ 2.92 1.70–4.98 3.88 1.93–7.82 OR: odds ratio; CI: confidence interval. #: includes the same population as in the fully adjusted model; ¶: yes versus no, major road is defined as ≥8,000 vehicles per 24 h; +: including city, sex, body mass index, age, smoking history, water damage or mould in the home at any time during the last 8 yrs.
- Table 5—
Results from the adjusted logistic regression model, describing the relationship between nitrogen dioxide and the risk of onset and incident asthma among males and females and subjects with and without hay fever and wheeze
Strata Onset asthma Incident asthma OR# 95% CI p-value for interaction OR# 95% CI p-value for interaction Females 1.30 0.96–2.04 0.71 1.67 0.98–2.74 0.63 Males 1.57 0.97–2.52 1.32 0.64–2.74 Hay fever 1.31 0.85–2.04 0.58 1.15 0.59–2.24 0.30 No hay fever 1.55 1.03–2.35 1.79 1.04–3.05 Wheeze 1.62 1.03–2.57 0.53 2.08 1.12–3.87 0.18 No wheeze 1.34 0.90–2.00 1.19 0.66–2.12 OR: odds ratio; CI: confidence interval. #: per 10 μg·m−3 from the fully adjusted model including city, sex, body mass index, age, smoking history and water damage or mould in the home at any time during the last 8 yrs.
Supplementary tables
Table 4a . Odds ratios for co-variates in the adjusted logistic regression model of the relationship between onset and incident asthma and modelled levels of nitrogen dioxide (NO2). Table 4b . Odds ratios for co-variates in the adjusted logistic regression model of the relationship between onset and incident asthma and living less than 50 meters from nearest major (>=8000 vehicles per 24 hours) road.
Files in this Data Supplement:
- Supplementary tables - Table 4a . Odds ratios for co-variates in the adjusted logistic regression model of the relationship between onset and incident asthma and modelled levels of nitrogen dioxide (NO2). Table 4b . Odds ratios for co-variates in the adjusted logistic regression model of the relationship between onset and incident asthma and living less than 50 meters from nearest major (>=8000 vehicles per 24 hours) road.
