Table 2.
Segmented poisson regression results *
| Monthly trend before law was passed (β 1 ) | Step change when law took effect (β 2 ) | Change in trend after law took effect (β 3 ) | Monthly trend after law took effect (β 1 + β 3 ) | |
|---|---|---|---|---|
| COPD | ||||
| β (SE) | -0.002 (0.002) | -0.091 (0.065) | -0.004 (0.004) | -0.006 (0.003) |
| RR (95% CI) | 0.998 (0.993, 1.002) | 0.913 (0.804, 1.036) | 0.994 (0.989, 0.999) | |
| p value | 0.331 | 0.158 | 0.313 | 0.028 |
| Asthma | ||||
| Overall | ||||
| β (SE) | +0.003 (0.002) | -0.206 (0.061) | -0.002 (0.003) | +0.000 (0.003) |
| RR (95% CI) | 1.003 (0.998, 1.007) | 0.814 (0.722, 0.918) | 1.000 (0.995, 1.005) | |
| p value | 0.236 | <0.001 | 0.502 | 0.876 |
| Adults | ||||
| β (SE) | -0.000 (0.003) | -0.175 (0.072) | +0.002 (0.004) | +0.002 (0.003) |
| RR (95% CI) | 1.000 (0.994, 1.005) | 0.840 (0.729, 0.966) | 1.002 (0.996, 1.008) | |
| p value | 0.922 | 0.015 | 0.611 | 0.552 |
| Children | ||||
| β (SE) | +0.011 (0.004) | -0.287 (0.118) | -0.015 (0.007) | -0.004 (0.005) |
| RR (95% CI) | 1.011 (1.002, 1.020) | 0.751 (0.595, 0.947) | 0.996 (0.986, 1.006) | |
| p value | 0.015 | 0.015 | 0.027 | 0.424 |
*The segmented Poisson regression model adjusted for age and sex provides estimates for the trend in ED visits over time prior to the law being passed (β1), the step change after the law took effect (β2) and the change in trend after the law took effect (β3). The sum of β1 and β3 corresponds to the trend over time after the law took effect.
Abbreviation: COPD chronic obstructive pulmonary disease.