Association of climatic factors with the 12 month period prevalence rates (in %) of symptoms of asthma, assessed by written questionnaire (WQ), in children; results of the multilevel linear regression analyses
| Worldwide* | Western Europe | |||
|---|---|---|---|---|
| 13–14 years RC† (95% CI) | 6–7 years RC† (95% CI) | 13–14 years RC† (95% CI) | 6–7 years RC† (95% CI) | |
| *Adjusted for GNP. | ||||
| †Regression coefficient with 95% confidence interval. | ||||
| ‡All centres had ⩾1 month with mean relative humidity indoors below 50%. | ||||
| Latitude (degrees) | −0.02 (−0.11 to 0.07) | −0.02 (−0.13 to 0.08) | 0.18 (−0.13 to 0.49) | −0.01 (−0.26 to 0.23) |
| Altitude (100 m) | −0.15 (−0.40 to 0.10) | −0.30 (−0.62 to 0.03) | −0.88 (−1.40 to −0.36) | −0.47 (−0.84 to −0.10) |
| Outdoor temperature | ||||
| Mean annual temperature (°C) | 0.06 (−0.10 to 0.23) | 0.06 (−0.18 to 0.31) | 0.37 (−0.15 to 0.89) | 0.12 (−0.29 to 0.54) |
| Annual variation in mean temperature (°C) | −0.31 (−1.30 to 0.69) | −0.06 (−1.38 to 1.26) | −5.00 (−8.43 to −1.57) | −4.10 (−6.22 to −1.98) |
| Lowest monthly mean temperature (°C) | 0.02 (−0.07 to 0.11) | 0.01 (−0.12 to 0.14) | 0.36 (0.03 to 0.69) | 0.31 (0.04 to 0.57) |
| Mean temperature of ⩾1 month below 0°C | −0.51 (−2.97 to 1.96) | −1.86 (−5.68 to 1.96) | −0.96 (−7.64 to 5.73) | −1.09 (−4.61 to 2.43) |
| Outdoor relative humidity | ||||
| Mean annual relative humidity (%) | −0.03 (−0.11 to 0.06) | −0.05 (−0.13 to 0.04) | 0.17 (−0.05 to 0.38) | 0.11 (−0.04 to 0.26) |
| Annual variation in mean relative humidity (%) | −0.31 (−1.13 to 0.51) | −0.12 (−0.86 to 0.62) | −1.84 (−3.06 to −0.62) | −1.13 (−1.91 to −0.35) |
| Lowest monthly mean relative humidity (%) | 0.00 (−0.05 to 0.06) | 0.00 (−0.05 to 0.04) | 0.13 (0.04 to 0.23) | 0.09 (0.02 to 0.15) |
| Mean relative humidity of ⩾1 month below 50% | 0.03 (−1.99 to 2.05) | 0.19 (−1.66 to 2.04) | −5.67 (−9.12 to −2.22) | −2.92 (−5.12 to −0.71) |
| Indoor relative humidity at 20°C | ||||
| Mean annual relative humidity (%) | 0.00 (−0.04 to 0.05) | −0.01 (−0.06 to 0.03) | 0.27 (0.10 to 0.45) | 0.15 (0.03 to 0.27) |
| Annual variation in mean relative humidity (%) | −0.01 (−0.43 to 0.42) | 0.12 (−0.22 to 0.47) | 0.41 (−0.68 to 1.49) | −0.12 (−0.91 to 0.68) |
| Lowest monthly mean relative humidity (%) | 0.02 (−0.03 to 0.06) | 0.00 (−0.04 to 0.04) | 0.26 (0.05 to 0.46) | 0.22 (0.08 to 0.36) |
| Mean relative humidity of ⩾1 month below 50% | 0.85 (−1.21 to 2.90) | 1.95 (−0.20 to 4.10) | * | * |