Acute effects of air pollution and extreme temperatures on cause-specific mortality in Italy. Results of the BIGEPI project.

Abstract

Air pollution and extreme temperatures have been associated with multiple adverse health effects, especially on the cardiovascular and respiratory systems. The evidence of a relationship between daily exposures and mortality from metabolic, nervous and mental causes needs to be strengthened. The aim of this study is to investigate the association between daily exposure to fine particulate matter (PM2.5) and extreme temperatures (heat and cold) with cause-specific mortality in the entire Italian population. The daily counts of deaths from natural, cardiovascular, respiratory, metabolic, diabetes, nervous and mental causes were provided by Istat at the municipal level for the period 2006-2015. Through the application of machine-learning models based on satellite data and spatiotemporal variables, population-weighted exposures to daily mean PM2.5 (2013-2015) and air temperature (2006-2015) were estimated at municipality level. Time-series models adjusted for seasonal and long-term trends were applied, and associations between the above exposures and different causes of death at the national level were estimated. The study found a marked effect of PM2.5 on deaths from nervous causes, with a % increase of risk (IR%) of 6.55% (95% confidence interval: 3.38%-9.81%) per PM2.5 increases of 10 µg/m3. The study also highlighted significant effects of low and high temperatures on all study outcomes. The effects were greater for high temperatures. In particular, the effects of heat, expressed as a % increase in risk per temperature increase from the 75th to the 99th percentile, show the highest associations with mortality from nervous causes (58.3%; 95%CI: 49.7%-67.5%), mental causes (48.4%; 95%CI: 40.4%-56.9%), respiratory causes 45.8%; 95%CI: 39.7%-52.1%) and metabolic causes (36.9%; 95%CI: 30.6%-43.5%). The study showed a strong association between daily exposure to PM2.5 and extreme temperatures, especially heat, with mortality outcomes, especially those under-investigated, such as diabetes, metabolic, nervous and mental causes.