title: Changing patterns of the temperature-mortality association by time and location in the US, and implications for climate change.
abstract: The shape of the non-linear relationship between temperature and mortality varies among cities with different climatic conditions. There has been little examination of how these curves change over space and time. We evaluated the short-term effects of hot and cold temperatures on daily mortality over six 7-year periods in 211 US cities, comprising over 42 million deaths. Cluster analysis was used to group the cities according to similar temperatures and relative humidity. Temperature-mortality functions were calculated using B-splines to model the heat effect (lag 0) and the cold effect on mortality (moving average lags 1-5). The functions were then combined through meta-smoothing and subsequently analyzed by meta-regression. We identified eight clusters. At lag 0, Cluster 5 (West Coast) had a RR of 1.14 (95% CI: 1.11,1.17) for temperatures of 27 °C vs 15.6 °C, and Cluster 6 (Gulf Coast) has a RR of 1.04 (95% CI: 1.03,1.05), suggesting that people are acclimated to their respective climates. Controlling for cluster effect in the multivariate-meta regression we found that across the US, the excess mortality from a 24-h temperature of 27 °C decreased over time from 10.6% to 0.9%. We found that the overall risk due to the heat effect is significantly affected by summer temperature mean and air condition usage, which could be a potential predictor in building climate-change scenarios.
authors.affiliation: TIMI Study Group, Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; Department of Environmental Health, Exposure, Epidemiology, and Risk Program, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Francesco
authors.initials: F
authors.lastname: Nordio
authors.affiliation: Department of Environmental Health, Exposure, Epidemiology, and Risk Program, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Antonella
authors.initials: A
authors.lastname: Zanobetti
authors.affiliation: Department of Environmental Health, Exposure, Epidemiology, and Risk Program, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Colicino
authors.affiliation: Department of Geography and Environmental Development, Ben-Gurion University of the Negev, Beer Sheva, Israel.
authors.forename: Itai
authors.initials: I
authors.lastname: Kloog
authors.affiliation: Department of Environmental Health, Exposure, Epidemiology, and Risk Program, Harvard School of Public Health, Boston, MA, USA. Electronic address: jschwrtz@hsph.harvard.edu.
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
mesh_terms: D002947:Cities; D057231:Climate Change; D016000:Cluster Analysis; D006801:Humans; D008962:Models, Theoretical; D009026:Mortality; D012306:Risk; D012621:Seasons; D013696:Temperature; D014481:United States / Q000453:epidemiology
keywords: Climate change; Health effects; Meta-smoothing; Temperature