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Table 5 Results of linear mixed models with random intercept on schools to investigate associations between short and medium term background air pollution and peak expiratory flow (n = 425)

From: Impact of close-proximity air pollution on lung function in schoolchildren in the French West Indies

 

O3(in μg/m3)

NO2(in μg/m3)

SO2(in μg/m3)

PM10(in μg/m3)

 

β

(95% CI)

β

(95% CI)

β

(95% CI)

β

(95% CI)

Medium-term exposure

        

Model 1

        

Pollutant

−0.44

(−2.61; 1.74)

−0.215

(−3.89; 3.46)

1.18

(−2.65; 5.00)

3.05

(0.04; 6.05)

Variability of school random intercept: \( {\widehat{\upsigma}}_{\upgamma 0}^2 \) (P value)

90.20 (0.05)

105.34 (0.11)

86.80 (0.04)

11.05 (0.50)

Model 2 (Interaction of pollutant with asthma)

        

Non-asthmatic children

−0.13

(−2.32; 2.07)

−0.56

(−4.27; 3.15)

0.67

(−3.20; 4.54)

2.95

(0.12; 5.78)

Asthmatic children

−1.88

(−4.50; 0.74)

1.40

(−2.97; 5.78)

3.54

(−1.06; 8.14)

3.48

(0.31; 6.64)

Variability of school random intercept: \( {\widehat{\upsigma}}_{\upgamma 0}^2 \) (P value)

89.30 (0.04)

107.99 (0.19)

91.89 (0.04)

19.82 (0.50)

Short-term exposure

        

Model 3

        

D0

−0.24

(−5.09; 4.61)

0.54

(−2.44; 3.51)

0.41

(−35.98; 36.80)

0.14

(−1.82; 2.09)

D1

−0.52

(−1.62; 0.58)

0.11

(−2.19; 2.42)

−0.53

(−14.32; 13.27)

0.55

(−1.94; 3.04)

D2

−0.56

(−4.06; 2.94)

−0.15

(−2.54; 2.24)

−1.03

(−4.21; 2.14)

0.79

(−2.17; 3.75)

D3

−0.37

(−3.68; 2.94)

−0.27

(−2.68; 2.14)

−1.11

(−14.25; 12.04)

0.87

(−2.19; 3.94)

D4

0.05

(−0.63; 0.73)

−0.23

(−2.60; 2.15)

−0.74

(−18.06; 16.56)

0.79

(−2.02; 3.59)

D5

0.70

(−4.99; 6.39)

−0.03

(−3.06; 2.99)

0.04

(−15.52; 15.60)

0.53

(−1.86; 2.92)

  Cumulative effect

−0.94

(−4.82; 2.95)

−0.03

(−14.01; 13.94)

−2.96

(−12.69; 6.77)

3.67

(−11.47; 18.81)

Variability of school random intercept \( {\widehat{\upsigma}}_{\upgamma 0}^2 \) (P value)

0.00 (0.50)

0.00 (0.50)

0.00 (0.50)

0.00 (0.50)

  1. Note. The peak expiratory flow (PEF) corresponds to baseline peak expiratory flow before running in children. The coefficients (β) and their 95% confidence interval were obtained using linear mixed models regarding models 1–2 and a distributed-lag model regarding model 3. Variables such as sex, age, body mass index, full-term birth, rainy season, temperature and relative humidity are forced in each model. Other confounding factors are included: atopy for model 1–2 and atopy, asthma and day of week for model 3.
  2. Short-term exposure was defined by the average of each pollutant concentration on the current day and up to five days corresponding to five different lags (D0, D1, D2, D3, D4, D5). These lags were classified into two categories: short-delay exposure and cumulative short delay exposure, which indicates the mean exposure to pollutants on the five preceding days.
  3. Abbreviations: PEF, peak expiratory flow; O3, ozone; NO2, nitrogen dioxide; SO2, sulphur dioxide; PM10, small particulate matter; CI, confidence interval.