A statistical model to identify excess mortality in Italy in the period 2011–2022

• Published in: European physical journal plus 2024-04, Vol.139 (4), p.348, Article 348
• Main Authors: Bella, Antonino, Bonifazi, Gianluca, Lista, Luca, Menasce, Dario, Mezzetto, Mauro, Pedrini, Daniele, Pezzotti, Patrizio, Rota, Maria Cristina, Spighi, Roberto, Zoccoli, Antonio
• Format: Article
• Language: English
• Subjects: Age; Applied and Technical Physics; Atomic; Casualties; Complex Systems; Condensed Matter Physics; COVID-19; Data analysis; Epidemics; Fatalities; Gender; Heat waves; Mathematical and Computational Physics; Maxima; Molecular; Mortality; Optical and Plasma Physics; Pandemics; Physics; Physics and Astronomy; Public health; Regular Article; Scandals; Statistical methods; Statistical models; Summer; Theoretical; Time series; Viral diseases; Winter
• ISSN: 2190-5444; 2190-5444
• DOI: 10.1140/epjp/s13360-024-05136-9

Excess mortality is defined as an increase in the number of deaths above what is expected based on historical trends, hereafter called baseline. In a previous paper, we introduced a statistical method that allows an unbiased and robust determination of the baseline to be used for the computation of excesses. A good determination of the baseline allows us to efficiently evaluate the excess of casualties that occurred in Italy in the last 12 years and in particular in the last 3 years due to the Coronavirus Disease 2019 (COVID-19) epidemic. To this extent, we have analyzed the data on mortality in Italy in the period January 1st 2011 to December 31th 2022, provided by the Italian National Institute of Statistics (ISTAT). The dataset contains information on deaths for all possible causes, without specific reference to any particular one. The data exhibit strikingly evident periodicity in the number of deaths with pronounced maxima in the winter and minima in the summer, repeating itself in amplitude along the whole twelve-year sample. Superimposed on this wave-like structure are often present excesses of casualties, most likely due to occasional causes of death such as the flu epidemics (in winter) and heat waves (in summer). The very accurate periodicity along the seasons (the “baseline”), allows us to determine with great accuracy and confidence the number of expected deaths for each day of the year in the absence of occasional contributions. Each of the latter can be modeled with an additional function that parameterizes the deviation from the baseline. We can then provide an unbiased way of measuring these excesses for each period of the year and for different categories of people (disentangling the sample by age and gender). The study has been extended to include an analysis of the data provided by the Italian Department for Civil Protection (DPC) and the Italian National Institute of Health (ISS), which specifically focuses on deaths labeled as resulting from the COVID-19 pandemic. The effect of COVID-19 on mortality is clearly visible since 2020; in Italy, the excess of deaths (until December 2022), directly or indirectly due to the COVID-19 pandemic, is estimated to be about 217 thousand distributed in 10 different pandemic waves.. The majority of deaths (approximately 95%) occurred in individuals over 60 years of age, and there is evidence indicating lower mortality rates among females. The excess of deaths has also been quantified by analyzing the d