Factors associated with increased all-cause mortality during the COVID-19 pandemic in Italy

Background: The number of excess deaths during February–March 2020 in Italy, in comparison with previous years, was considerably higher than the recorded COVID19-related deaths. The present study aimed to explore the association of excess mortality with some indices related to the COVID-19 pandemic and its management. Methods: Data on all-cause mortality from 20 February–31 March in the years 2015–2020, and demographic, socioeconomic and healthcare organisation data of each Italian region were obtained from the Italian Institute of Statistics. Non-COVID-19-Imputed Excess Mortality (NCIEM) was calculated as the difference between the excess 2020 mortality and reported COVID-19 mortality. The association of NCIEM with the rate of COVID-19 cases, COVID-19 mortality and other potential moderators was assessed using linear regression models. Results: The nationwide number of excess deaths and COVID-19 deaths was 26,701 and 13,710, respectively, with a difference of 12,991. The NCIEM in different regions showed a direct correlation with COVID-19 mortality (r2 = 0.61, p < 0.001) and total cases (r2 = 0.30, p = 0.012), and an inverse correlation with cases/total tests ratio (r2 = 0.49, p = 0.001). Direct correlations were also found with the proportion of institutionalised elderly, whereas inverse correlations were observed with prevalence of diabetes, cardiovascular mortality and density of general practitioners. Conclusions: The impact of the COVID-19 pandemic on all-cause mortality was considerably greater than that indicated by official counts of victims. Limited testing capacity and causes of death other than COVID-19 could have contributed to the increase in overall mortality rates.