Period life expectancy is one of the most used summary indicators for the overall health of a population. Its levels and trends direct health policies, and researchers try to identify the determining risk factors to assess and forecast future developments. The use of period life expectancy is often based on the assumption that it directly reflects the mortality conditions of a certain year. Accordingly, the explanation for changes in life expectancy are typically sought in factors that have an immediate impact on current mortality conditions. It is frequently overlooked, however, that this indicator can also be affected by at least three kinds of effects, in particular in the situation of short-term fluctuations: cohort effects, heterogeneity effects, and tempo effects. We demonstrate their possible impact with the example of the almost Europe-wide decrease in life expectancy in 2015, which caused a series of reports about an upsurge of a health crisis, and we show that the consideration of these effects can lead to different conclusions. Therefore, we want to raise an awareness concerning the sensitivity of life expectancy to sudden changes and the menaces a misled interpretation of this indicator can cause.

Existing studies commonly rely on national official reports to estimate the impact of COVID-19 on human life. This is problematic because classification, estimation and reporting of COVID-19 mortality are not consistent across countries. To overcome these problems, this study exploits all cause daily death registrations data provided by the Italian Statistical Office (ISTAT) from January 1 to April 15, 2020. This allows us to: 1) calculate excess mortality in 2020 compared to the average of the years 2015 to 2019; and 2) estimate life expectancy on a seasonal and annual basis. Focusing on the five most severely hit provinces in Italy (Bergamo, Brescia, Cremona, Lodi and Piacenza) and Lombardy region, this analysis captures the impact of COVID-19 on mortality and life expectancy, which are likely to be underestimated when only national level data are considered. We find that seasonal life expectancy in 2020 in the five provinces reduced by 5.1 to 7.8 and 3.2 to 5.8 years for men and women, respectively. For annual life expectancy for the year 2020, in a scenario with no harvesting effect i.e. mortality rates resume to an average level of the years 2015-2019 after the end of the first epidemic wave, the years of life lost is equivalent to 2 to 3.5 years for men and 1.1. to 2.5 years for women in the five provinces. This represents the largest decline in life expectancy after the 1918 influenza pandemic and the Second World War.