Excess mortality during the COVID-19 outbreak in Italy: a two-stage interrupted time series analysis

Abstract

AbstractBackgroundItaly was the first country outside China to experience the impact of the COVID-19 pandemic, which resulted in a significant health burden. This study presents an analysis of the excess mortality across the 107 Italian provinces, stratified by sex, age group, and period of the outbreak.MethodsThe analysis was performed using a two-stage interrupted time series design using daily mortality data for the period January 2015 – May 2020. In the first stage, we performed province-level quasi-Poisson regression models, with smooth functions to define a baseline risk while accounting for trends and weather conditions and to flexibly estimate the variation in excess risk during the outbreak. Estimates were pooled in the second stage using a mixed-effects multivariate meta-analysis.ResultsIn the period 15 February – 15 May 2020, we estimated an excess of 47,490 (95% empirical confidence intervals: 43,984 to 50,362) deaths in Italy, corresponding to an increase of 29.5% (95%eCI: 26.8 to 31.9%) from the expected mortality. The analysis indicates a strong geographical pattern, with the majority of excess deaths occurring in northern regions, where few provinces experienced up to 800% increase during the peak in late March. There were differences by sex, age, and area both in the overall impact and in its temporal distribution.ConclusionsThis study offers a detailed picture of excess mortality during the first months of the COVID-19 pandemic in Italy. The strong geographical and temporal patterns can be related to implementation of lockdown policies and multiple direct and indirect pathways in mortality risk.Key MessagesThis study evaluated mortality trends in Italy during the COVID-19 pandemic, reporting an excess of 47,490 (95% empirical confidence intervals: 43,984 to 50,362) deaths in the period 15 February – 15 May 2020, corresponding to an increase of 29.5% (95%eCI: 26.8 to 31.9%) from the expected mortality.There is a strong geographical pattern, with 71.0% of the estimated excess deaths occurring in just three northern regions (Lombardy, Veneto, and Emilia-Romagna), and few provinces showing increases in mortality up to 800% during the peak of the pandemic.The impact was slightly higher is men compared to women, with 24,655 and 23,125 excess deaths respectively, and varied by age, with higher mortality in the group 70-79 years old and evidence of a lower but measurable risk even in people less than 60.The analysis by week suggests differential trends, with more delayed impacts in women and elderly, and the risk limited to the early period in Central and Southern Italy, likely related to the implementation of lockdown policies and contributions from direct and indirect risk pathways.