Table 3.
Distribution of the daily number of ER admissions for respiratory diseases and daily concentrations of chemical air pollution and aeroallergens during the study period, according to the potential confounders considered in the analysisa
| ER admissions (counts) | PM2.5 (μg/m3) | NO2 (μg/m3) | O3 (μg/m3) | Aeroallergens (grains/m3) | |
|---|---|---|---|---|---|
| Day of the week | |||||
| Monday | 22.7 ± 10.2 | 30.4 ± 26.5 | 47.2 ± 25.1 | 38.2 ± 27.7 | 12.7 ± 20.9 |
| Tuesday | 21.4 ± 9.8 | 30.8 ± 25.4 | 50.3 ± 24.5 | 37.8 ± 28.6 | 14.9 ± 28.8 |
| Wednesday | 20.4 ± 9.6 | 32.5 ± 25.4 | 51.0 ± 23.8 | 38.9 ± 29.2 | 18.8 ± 38.1 |
| Thursday | 21.6 ± 9.7 | 35.1 ± 27.8 | 52.9 ± 25.9 | 38.9 ± 30.2 | 15.1 ± 23.0 |
| Friday | 23.4 ± 11.1 | 33.3 ± 25.0 | 50.9 ± 24.7 | 39.9 ± 29.7 | 17.2 ± 32.1 |
| Saturday | 31.1 ± 12.4 | 31.5 ± 26.0 | 45.0 ± 25.1 | 42.2 ± 29.8 | 18.2 ± 33.4 |
| Sunday | 32.2 ± 12.8 | 30.4 ± 27.4 | 40.9 ± 24.0 | 41.3 ± 28.5 | 15.8 ± 27.4 |
| p | <0.001 | 0.79 | 0.002 | 0.87 | 0.73 |
| Holidays | |||||
| Christmas and Easter | 47.6 ± 17.5 | 25.4 ± 15.2 | 45.1 ± 27.5 | 32.0 ± 29.9 | 1.0 ± 1.9 |
| 3 days before/after Christmas and Easter | 34.9 ± 16.3 | 37.9 ± 21.7 | 58.6 ± 25.8 | 25.7 ± 23.7 | 6.4 ± 15.8 |
| Other holidays | 35.6 ± 15.6 | 37.4 ± 27.7 | 49.3 ± 22.7 | 32.2 ± 30.4 | 12.6 ± 1.9 |
| Other days | 23.8 ± 10.9 | 31.6 ± 26.4 | 48.0 ± 25.0 | 40.4 ± 29.1 | 16.6 ± 30.2 |
| p | <0.001 | 0.39 | 0.23 | 0.02 | 0.20 |
| Influenza outbreaks | |||||
| No | 19.9 ± 9.0 | 22.8 ± 21.0 | 36.8 ± 16.9 | 55.2 ± 27.4 | 23.8 ± 31.9 |
| Yes | 31.0 ± 12.0 | 43.9 ± 27.5 | 63.0 ± 25.8 | 19.9 ± 16.4 | 6.3 ± 23.0 |
| p | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 |
| Summer population decrease | |||||
| 2 weeks around 15 August | 13.4 ± 4.71 | 15.8 ± 5.6 | 20.7 ± 6.3 | 66.1 ± 15.4 | 34.7 ± 28.5 |
| From 16/7 to 31/8 (except 2 weeks around 15 August) | 14.4 ± 5.8 | 14.5 ± 6.4 | 26.1 ± 8.5 | 78.0 ± 19.3 | 29.1 ± 31.6 |
| Other days | 26.4 ± 11.6 | 34.5 ± 27.1 | 52.5 ± 24.5 | 33.7 ± 26.3 | 13.4 ± 28.7 |
| p | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 |
| Temperatureb (°C) | |||||
| −6.4, 6.4 | 29.1 ± 11.6 | 57.3 ± 28.3 | 78.9 ± 27.6 | 12.1 ± 8.8 | 0.8 ± 2.5 |
| 6.5, 12.8 | 28.1 ± 11.3 | 31.7 ± 21.5 | 51.7 ± 15.2 | 23.3 ± 17.3 | 10.1 ± 31.9 |
| 12.9, 20.3 | 24.8 ± 11.5 | 27.5 ± 23.9 | 43.4 ± 17.1 | 41.2 ± 20.2 | 14.9 ± 21.6 |
| 20.4, 28.5 | 19.5 ± 8.2 | 14.9 ± 6.8 | 29.4 ± 9.5 | 73.7 ± 18.4 | 32.5 ± 39.7 |
| p | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 |
| Cumulative precipitation | |||||
| <1 mm | 25.4 ± 11.4 | 35.5 ± 28.0 | 51.5 ± 26.2 | 38.0 ± 33.7 | 16.0 ± 29.9 |
| ≥1 mm | 25.2 ± 11.5 | 25.5 ± 19.2 | 45.0 ± 20.1 | 33.7 ± 26.0 | 9.5 ± 27.3 |
| p | 0.87 | <0.001 | 0.01 | 0.10 | 0.02 |
| Relative humidity b(%) | |||||
| 30.4, 60.4 | 26.4 ± 10.3 | 17.8 ± 13.1 | 41.6 ± 17.9 | 52.1 ± 24.6 | 25.1 ± 34.3 |
| 60.5, 68.6 | 23.1 ± 11.6 | 25.5 ± 18.9 | 43.2 ± 22.2 | 50.9 ± 31.3 | 21.8 ± 37.5 |
| 68.7, 76.4 | 25.3 ± 11.3 | 44.7 ± 30.5 | 56.9 ± 32.1 | 28.3 ± 23.0 | 9.6 ± 25.4 |
| 76.5, 85.5 | 26.7 ± 12.1 | 42.5 ± 28.8 | 58.4 ± 22.1 | 16.7 ± 15.9 | 1.9 ± 6.0 |
| p | 0.01 | <0.001 | <0.001 | <0.001 | <0.001 |
amean ± SD reported; overall p-values were calculated using non-parametric Kruskall-Wallis tests, under the null hypothesis that the distribution of a variables is homogeneous among the strata of a potential confounder
b coded in groups according to the quartiles of their frequency distribution