Crude and adjusted associations between level of physical activity and number of COPD admissions in COPD subjects (zero-inflated negative binomial regression)
| n* | Crude IRR(95% CI) | p value | Adjusted† IRR(95% CI) | p value | |
|---|---|---|---|---|---|
| IRR, incident rate ratio; CI, confidence interval. | |||||
| *The number of subjects may be lower in the multivariate models as some values are missing for certain variables (see tables 1 and 2). One subject was excluded from the zero-inflated negative binomial regression model for recording 65 COPD admissions during follow up (outlier value). | |||||
| †Multivariate model adjusted for sputum and FEV1 in the count component, and for age, ischaemic heart disease, smoking habit, sputum, visits to doctor, and FEV1 in the zero-inflated component of the zero-inflated negative binomial regression. | |||||
| Physical activity (combined) | |||||
| Very low | 219 | 1 | 1 | ||
| Low/moderate/high | 2155 | 0.63 (0.46 to 0.86) | 0.004 | 0.72 (0.53 to 0.97) | 0.033 |
| Physical activity (categories) | |||||
| Very low | 219 | 1 | 1 | ||
| Low | 294 | 0.73 (0.49 to 1.08) | 0.113 | 0.77 (0.53 to 1.14) | 0.192 |
| Moderate | 1089 | 0.63 (0.45 to 0.88) | 0.006 | 0.68 (0.49 to 0.93) | 0.018 |
| High | 772 | 0.57 (0.40 to 0.82) | 0.002 | 0.76 (0.53 to 1.08) | 0.121 |
| p for linear trend | 0.002 | 0.104 | |||