14 / 2021-06-01 08:05:17

Temperature-mortality association during and before the COVID-19 pandemic in Italy: A nationwide time-stratified case-crossover study

non-COVID-19 deaths,all-cause mortality,temperature,pandemic,Italy

Background: Human lives and the health system have been substantially reshaped by the COVID‐19 pandemic. However, the impacts of temperature on non-COVID and all-cause mortality in the pandemic remains unknown.

Objectives: We aimed to identify the associations of temperature with non-COVID and all-cause deaths in the pandemic 2020 in comparison with the non-COVID-19 period in Italy.

Methods: The daily data on 3,958,989 all-cause deaths (including 3,885,308 non-COVID deaths) and meteorological conditions in 107 Italian provinces between 2015 and 2020 was collected. We employed a time-stratified case-crossover study design combined with the DLNM model to investigate the relationships of temperature with all-cause and non-COVID deaths in 2020 and 2015-2019.

Results: Cold temperature contributed higher risks for both all-cause and non-COVID deaths in the pandemic year 2020 than in 2015-2019. However, no different change was found for the impacts of hot temperature. The relative risk (RR) of non-COVID deaths and all-cause mortality at extremely cold temperature (2 ˚C) in comparison with the estimated minimum mortality temperature (19 ˚C) in 2020 were 1.63 (95% CI: 1.55-1.72) and 1.45 (95%CI: 1.31-1.61) respectively, which were higher than all-cause mortality risk in 2015-2019 with RR of 1.19 (95%CI: 1.17-1.21). A total of 72,914 (95%CI: 66,063-80,658) all-cause deaths and 50,408 (95%CI: 42,088-58,371) non-COVID deaths were attributable to cold temperatures in 2020 pandemic period. Males (RR of 1.74 (95%CI: 1.63-1.86)) suffered greater risk of dying due to extremely cold temperature than females (RR of 1.54 (95%CI: 1.44-1.64)) in the pandemic, but no significant change in temperature-mortality association was found for people above 85 years old between the periods of 2015-2019 and 2020.

Discussion: Cold temperature showed stronger impacts than hot temperature on all-cause and non-COVID mortality in the pandemic year 2020 compared to pre-pandemic periods in Italy. Thus, taking actions to avoid the cold-related excess mortality is critical in the pandemic.