Table 3. The relative risk for pediatric outpatient visits for asthma during 20-day cold spell in 2008 compared with the same periods in 2007 and 2009a.
| Lag | RR (95% CI) | |||
| Model 1b | Model 2c | Model 3d | Model 4e | |
| Lag 0 | 1.40 (1.21, 1.61) | 1.37 (1.18, 1.58) | 1.45 (1.26, 1.67) | 1.41 (1.22, 1.63) |
| Lag 1–2 | 1.44 (1.25, 1.66) | 1.42 (1.22, 1.64) | 1.51 (1.30, 1.75) | 1.46 (1.25, 1.72) |
| Lag 3–6 | 1.47 (1.29, 1.68) | 1.46 (1.27, 1.67) | 1.49 (1.30, 1.71) | 1.47 (1.27, 1.72) |
| Lag 7–14 | 1.71 (1.46, 1.99) | 1.66 (1.41, 1.96) | 1.75 (1.49, 2.06) | 1.70 (1.43, 2.02) |
| Lag 15–30 | 1.68 (1.50, 1.93) | 1.71 (1.43, 2.03) | 1.72 (1.48, 2.00) | 1.65 (1.36, 2.00) |
| Lag 1–30 | 1.62 (1.46, 1.79) | 1.63 (1.46, 1.82) | 1.65 (1.48, 1.84) | 1.64 (1.46, 1.84) |
a
All the models were adjusted for day of the week, season and long-term trend; and all RRs were statistically significant (P<0.01);
b
Model 1 did not controlled for relative humidity and O3;
c
Model 2 controlled for relative humidity;
d
Model 3 controlled for O3;
e
Model 4 controlled for relative humidity and O3;