Table 3.
Adjusted long-term associations between air pollutants and COVID-19-related outcomes in single-pollutant models by COVID-19 waves
| First wave | Second wave | ||
|---|---|---|---|
| Exposure | HR (95% CI) | HR (95% CI) | |
| Hospitalization | |||
| NO2 (IQR increase: 16.1) | 1.32 (1.27–1.37) | 1.16 (1.11–1.22) | |
| PM2.5 (IQR increase: 3.2) | 1.25 (1.21–1.28) | 1.11 (1.07–1.14) | |
| ICU admission | |||
| NO2 (IQR increase: 16.1) | 1.48 (1.32–1.67) | 1.34 (1.18–1.53) | |
| PM2.5 (IQR increase: 3.2) | 1.19 (1.09–1.30) | 1.12 (1.02–1.23) | |
| Death | |||
| NO2 (IQR increase: 16.1) | 1.15 (1.06–1.25) | 1.25 (1.10–1.41) | |
| PM2.5 (IQR increase: 3.2) | 1.12 (1.06–1.20) | 1.14 (1.04–1.25) | |
| Hospital LOS | |||
| NO2 (IQR increase: 16.1) | 1.06 (1.03–1.10) | 1.03 (0.99–1.06) | |
| PM2.5 (IQR increase: 3.2) | 1.07 (1.04–1.09) | 1.05 (1.02–1.07) | |
Time-stratified Cox model adjusted as Model 4: age (continuous term, penalized spline with 6 df) + sex (strata, 2 categories) + smoking status (factor, 3 categories) + individual income (factor, 3 categories) + health risk group (factor, 4 categories) + small area socioeconomic index (continuous term) + percentage of non-Spanish nationals (continuous term) + distance to the closest primary care unit (continuous term) + urbanicity (strata, 3 categories) + average weekly of test-positive proportion (continuous term) + health region (strata, 7 categories)