title: Changes in Susceptibility to Heat During the Summer: A Multicountry Analysis.
abstract: Few studies have examined the variation in mortality risk associated with heat during the summer. Here, we apply flexible statistical models to investigate the issue by using a large multicountry data set. We collected daily time-series data of temperature and mortality from 305 locations in 9 countries, in the period 1985-2012. We first estimated the heat-mortality relationship in each location with time-varying distributed lag non-linear models, using a bivariate spline to model the exposure-lag-response over lag 0-10. Estimates were then pooled by country through multivariate meta-analysis. Results provide strong evidence of a reduction in risk over the season. Relative risks for the 99th percentile versus the minimum mortality temperature were in the range of 1.15-2.03 in early summer. In late summer, the excess was substantially reduced or abated, with relative risks in the range of 0.97-1.41 and indications of wider comfort ranges and higher minimum mortality temperatures. The attenuation is mainly due to shorter lag periods in late summer. In conclusion, this multicountry analysis suggests a reduction of heat-related mortality risk over the summer, which can be attributed to several factors, such as true acclimatization, adaptive behaviors, or harvesting effects. These findings may have implications on public health policies and climate change health impact projections.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gasparrini
authors.forename: Yuming
authors.initials: Y
authors.lastname: Guo
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hashizume
authors.forename: Eric
authors.initials: E
authors.lastname: Lavigne
authors.forename: Aurelio
authors.initials: A
authors.lastname: Tobias
authors.forename: Antonella
authors.initials: A
authors.lastname: Zanobetti
authors.forename: Joel D
authors.initials: JD
authors.lastname: Schwartz
authors.forename: Michela
authors.initials: M
authors.lastname: Leone
authors.forename: Paola
authors.initials: P
authors.lastname: Michelozzi
authors.forename: Haidong
authors.initials: H
authors.lastname: Kan
authors.forename: Shilu
authors.initials: S
authors.lastname: Tong
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Honda
authors.forename: Ho
authors.initials: H
authors.lastname: Kim
authors.forename: Ben G
authors.initials: BG
authors.lastname: Armstrong
mesh_terms: D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D009026:Mortality; D017711:Nonlinear Dynamics; D015203:Reproducibility of Results; D012621:Seasons; D013997:Time Factors
keywords: adaptation; climate change; distributed lag models; heat; mortality; temperature