The role of humidity in associations of high temperature with mortality : a multicountry, multicity study

Armstrong, Ben and Sera, Francesco and Vicedo-Cabrera, Ana Maria and Abrutzky, Rosana and Åström, Daniel Oudin and Bell, Michelle L. and Chen, Bing-Yu and de Sousa Zanotti Stagliorio Coelho, Micheline and Correa, Patricia Matus and Dang, Tran Ngoc and Diaz, Magali Hurtado and Dung, Do Van and Forsberg, Bertil and Goodman, Patrick and Guo, Yue-Liang Leon and Guo, Yuming and Hashizume, Masahiro and Honda, Yasushi and Indermitte, Ene and Íñiguez, Carmen and Kan, Haidong and Kim, Ho and Kyselý, Jan and Lavigne, Eric and Michelozzi, Paola and Orru, Hans and Ortega, Nicolás Valdés and Pascal, Mathilde and Ragettli, Martina S. and Saldiva, Paulo Hilario Nascimento and Schwartz, Joel and Scortichini, Matteo and Seposo, Xerxes and Tobias, Aurelio and Tong, Shilu and Urban, Aleš and De la Cruz Valencia, César and Zanobetti, Antonella and Zeka, Ariana and Gasparrini, Antonio. (2019) The role of humidity in associations of high temperature with mortality : a multicountry, multicity study. Environmental Health Perspectives, 127 (9). p. 97007.

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Official URL: https://edoc.unibas.ch/72059/

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There is strong experimental evidence that physiologic stress from high temperatures is greater if humidity is higher. However, heat indices developed to allow for this have not consistently predicted mortality better than dry-bulb temperature.; We aimed to clarify the potential contribution of humidity an addition to temperature in predicting daily mortality in summer by using a large multicountry dataset.; In 445 cities in 24 countries, we fit a time-series regression model for summer mortality with a distributed lag nonlinear model (DLNM) for temperature (up to lag 3) and supplemented this with a range of terms for relative humidity (RH) and its interaction with temperature. City-specific associations were summarized using meta-analytic techniques.; Adding a linear term for RH to the temperature term improved fit slightly, with an increase of 23% in RH (the 99th percentile anomaly) associated with a 1.1% [95% confidence interval (CI): 0.8, 1.3] decrease in mortality. Allowing curvature in the RH term or adding terms for interaction of RH with temperature did not improve the model fit. The humidity-related decreased risk was made up of a positive coefficient at lag 0 outweighed by negative coefficients at lags of 1-3 d. Key results were broadly robust to small model changes and replacing RH with absolute measures of humidity. Replacing temperature with apparent temperature, a metric combining humidity and temperature, reduced goodness of fit slightly.; The absence of a positive association of humidity with mortality in summer in this large multinational study is counter to expectations from physiologic studies, though consistent with previous epidemiologic studies finding little evidence for improved prediction by heat indices. The result that there was a small negative average association of humidity with mortality should be interpreted cautiously; the lag structure has unclear interpretation and suggests the need for future work to clarify. https://doi.org/10.1289/EHP5430.
Faculties and Departments:09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Environmental Exposures and Health Systems Research > Physical Hazards and Health (Röösli)
UniBasel Contributors:Ragettli, Martina
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:National Institute of Environmental Health Sciences
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:30 Sep 2019 07:19
Deposited On:30 Sep 2019 07:19

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