Table 2.
Multivariable estimates of incidence rate ratios (IRRs) for COVID-19 in Lombardy municipalities between February 20th and April 16th, 2020, according to demographic, socioeconomic and community variables and air pollutants concentrations.
| Model with PM2.5 | Model with PM10 | ||||||
| IRRa | 95% CI | p-value | IRRa | 95% CI | p-value | ||
| Demographic, socioeconomic and community variables | |||||||
| Population sizeb | 0.90 | 0.83–0.98 | 0.01 | 0.90 | 0.83–0.98 | 0.01 | |
| Population densityb | 0.92 | 0.83–1.01 | 0.07 | 0.92 | 0.84–1.01 | 0.10 | |
| Sex ratioc | 0.99 | 0.94–1.05 | 0.83 | 1.00 | 0.94–1.05 | 0.87 | |
| Proportion of population over 75 years oldc | 1.08 | 1.01–1.15 | 0.02 | 1.09 | 1.02–1.16 | 0.01 | |
| Average family sizec | 1.01 | 0.95–1.08 | 0.79 | 1.03 | 0.97–1.10 | 0.33 | |
| House crowding index (high vs low) | 0.93 | 0.84–1.03 | 0.19 | 0.92 | 0.83–1.02 | 0.12 | |
| High to low education ratiob | 0.76 | 0.72–0.81 | <0.01 | 0.76 | 0.72–0.81 | <0.01 | |
| IRPEF per capitac | 1.19 | 1.12–1.27 | <0.01 | 1.18 | 1.11–1.26 | <0.01 | |
| Percentage of private mobility usec | 0.85 | 0.81–0.88 | <0.01 | 0.85 | 0.81–0.89 | <0.01 | |
| Number of beds in nursing homes (>80 vs 0) | 1.49 | 1.32–1.69 | <0.01 | 1.49 | 1.32–1.68 | <0.01 | |
| Distance to the closest hospitalc | 0.92 | 0.87–0.97 | <0.01 | 0.92 | 0.88–0.97 | <0.01 | |
| Number of employees in bars, restaurants and mobile catering activities per capita (>14 vs ≤ 9 per 1000 inhabitants) | 1.11 | 1.00–1.23 | 0.04 | 1.12 | 1.02–1.24 | 0.02 | |
| Number of employees in health and social assistance activities per capita (>0.6 vs 0 per 1000 inhabitants) | 1.02 | 0.92–1.14 | 0.70 | 1.02 | 0.92–1.14 | 0.66 | |
| Number of employees in sports, entertainment and recreational activities per capita (>0.9 vs ≤ 0.4 per 1000 inhabitants) | 1.18 | 1.07–1.30 | <0.01 | 1.18 | 1.07–1.31 | <0.01 | |
| Air pollutants concentrations | |||||||
| PM (per 10 μg/m3) | 1.58 | 1.31–1.90 | <0.01 | 1.34 | 1.16–1.55 | <0.01 | |
| NO2 (per 10 μg/m3) | 0.93 | 0.88–0.99 | 0.02 | 0.95 | 0.89–1.00 | 0.07 | |
Abbreviations: CI, confidence interval; IRPEF, Imposta Regionale Persone Fisiche; IRR, incidence rate ratio; NO2, nitrogen dioxide; PM, particulate matter.
a
Adjusted by weeks since first COVID-19 case report (a proxy for epidemic stage), winter average temperature and winter average absolute humidity as modelled through a 3-knots restrcited cubic spline (Fig. 4).
b
Variable was log2- transformed and standardized.
c
Variable was standardized.