2015 Excess mortality in Italy: the role of an ageing population, heat waves and factors influencing seasonal mortality

INTRODUCTION: 2015 registered excess deaths throughout Europe. The Italian National Institute of Statistics estimated an increase in mortality of +11.3% (45000 excess deaths) between January-August 2015 compared to 2014 creating great media attention. The study aims to evaluate the excess mortality in considering factors influencing seasonal mortality (extreme weather events, flu epidemics) and population dynamics. METHODS: Daily deaths from the rapid mortality surveillance system and temperature data from the National Heat Plan operational in 32 major Italian cities were used. Standardized mortality rates (deaths per 100,000) were calculated by month and age class for the period 2012-2015 to allow a comparison across years. Annual population data was applied to standardize class-specific mortality rates. RESULTS: In winter (January-March) 2015 mortality rates were significantly higher than previous years only among the very old subjects (85-89, 90+ years). A similar excess was observed in other European countries and was related to the predominant strain of influenza that was particularly virulent. During summer 2015 an increase in heat-related deaths was registered across Europe associated to heat wave events. In Italy, excess deaths among the elderly (65+) increased by 23% during the intense heat wave of July 2015; mortality rates were higher than previous years not only among the very old but also in the younger age classes (55-64 years). Overall, excess deaths in 2015 could also be explained by the lower-than-expected mortality in the two previous years which “inflated” the pool of susceptible elderly subjects. Another factor worth mentioning is the abrupt increase in the elderly in Italy due to post war demographic boom. Conclusions: The use of rapid mortality surveillance data and methods to estimate the impact are important for the planning of public health response measures to both extreme weather events and risk factors influencing seasonal mortality.