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. 2020 Sep 28;6(3):00458-2020.
doi: 10.1183/23120541.00458-2020. eCollection 2020 Jul.

Magnitude and time-course of excess mortality during COVID-19 outbreak: population-based empirical evidence from highly impacted provinces in northern Italy

Sara Conti  1 , Pietro Ferrara  1 , Giampiero Mazzaglia  1 , Marco I D'Orso  1 , Roberta Ciampichini  2 , Carla Fornari  1 , Fabiana Madotto  1   3 , Michele Magoni  4 , Giuseppe Sampietro  2 , Andrea Silenzi  4   5 , Claudio V Sileo  4 , Alberto Zucchi  2 , Giancarlo Cesana  1 , Lamberto Manzoli  6 , Lorenzo G Mantovani  1   3
Affiliations

Magnitude and time-course of excess mortality during COVID-19 outbreak: population-based empirical evidence from highly impacted provinces in northern Italy

Sara Conti et al. ERJ Open Res. .

Abstract

Background: The real impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on overall mortality remains uncertain as surveillance reports have attributed a limited number of deaths to novel coronavirus disease 2019 (COVID-19) during the outbreak. The aim of this study was to assess the excess mortality during the COVID-19 outbreak in highly impacted areas of northern Italy.

Methods: We analysed data on deaths that occurred in the first 4 months of 2020 provided by the health protection agencies (HPAs) of Bergamo and Brescia (Lombardy), building a time-series of daily number of deaths and predicting the daily standardised mortality ratio (SMR) and cumulative number of excess deaths through a Poisson generalised additive model of the observed counts in 2020, using 2019 data as a reference.

Results: We estimated that there were 5740 (95% credible set (CS) 5552-5936) excess deaths in the HPA of Bergamo and 3703 (95% CS 3535-3877) in Brescia, corresponding to a 2.55-fold (95% CS 2.50-2.61) and 1.93 (95% CS 1.89-1.98) increase in the number of deaths. The excess death wave started a few days later in Brescia, but the daily estimated SMR peaked at the end of March in both HPAs, roughly 2 weeks after the introduction of lockdown measures, with significantly higher estimates in Bergamo (9.4, 95% CI 9.1-9.7).

Conclusion: Excess mortality was significantly higher than that officially attributed to COVID-19, disclosing its hidden burden likely due to indirect effects on the health system. Time-series analyses highlighted the impact of lockdown restrictions, with a lower excess mortality in the HPA where there was a smaller delay between the epidemic outbreak and their enforcement.

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Conflict of interest statement

Conflict of interest: S. Conti has nothing to disclose. Conflict of interest: P. Ferrara has nothing to disclose. Conflict of interest: G. Mazzaglia has nothing to disclose. Conflict of interest: M.I. D'Orso has nothing to disclose. Conflict of interest: R. Ciampichini has nothing to disclose. Conflict of interest: C. Fornari has nothing to disclose. Conflict of interest: F. Madotto has nothing to disclose. Conflict of interest: M. Magoni has nothing to disclose. Conflict of interest: G. Sampietro has nothing to disclose. Conflict of interest: A. Silenzi has nothing to disclose. Conflict of interest: C.V. Sileo has nothing to disclose. Conflict of interest: A. Zucchi has nothing to disclose. Conflict of interest: G. Cesana has nothing to disclose. Conflict of interest: L. Manzoli has nothing to disclose. Conflict of interest: L.G. Mantovani has nothing to disclose.

Figures

FIGURE 1
FIGURE 1
Comparison of 2020 and 2019 cumulative daily counts of death from 1 January to 30 April, stratified by health protection agency (HPA).
FIGURE 2
FIGURE 2
Predicted standardised mortality ratio (SMR) from 1 January to 30 April 2020. Results from the overall analysis and from analyses stratified by age or sex, by health protection agency (HPA).
FIGURE 3
FIGURE 3
Estimated cumulative excess deaths and percentage increase compared to 2019, over the period 1 January to 30 April 2020, stratified by health protection agency (HPA) and age or sex.
FIGURE 4
FIGURE 4
Time-series of daily number of deaths, stratified by health protection agency (HPA). a) 21 February: first confirmed case in Lombardy; b) 22 February: lockdown and quarantine for 11 municipalities; c) 25 February: schools closed and crowd restrictions in six northern regions; d) 4 March: schools closed and crowd restrictions extended to the whole country, e) 7 March: lockdown and quarantine for Lombardy and 14 provinces, f) 11 March: lockdown and quarantine extended to the whole country.
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References

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