The Role of Humidity in Associations of High Temperature with Mortality: A Multicountry, Multicity Study.
- Armstrong B Department of Public Health, Environments and Society, London School of Hygiene and Tropical Medicine, London, UK.
- Sera F Department of Public Health, Environments and Society, London School of Hygiene and Tropical Medicine, London, UK.
- Vicedo-Cabrera AM Department of Public Health, Environments and Society, London School of Hygiene and Tropical Medicine, London, UK.
- Abrutzky R Universidad de Buenos Aires, Facultad de Ciencias Sociales, Instituto de Investigaciones Gino Germani, Buenos Aires, Argentina.
- Åström DO Section of Sustainable Health, Department of Occupational and Environmental Medicine, Umeå University, Umeå, Sweden.
- Bell ML School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA.
- Chen BY National Institute of Environmental Health Science, National Health Research Institutes, Zhunan, Taiwan.
- de Sousa Zanotti Stagliorio Coelho M Institute of Advanced Studies, University of São Paulo, São Paulo, Brazil.
- Correa PM Department of Public Health, Universidad de los Andes, Santiago, Chile.
- Dang TN Institute of Research and Development, Duy Tan University, Da Nang, Vietnam.
- Diaz MH Department of Environmental Health, National Institute of Public Health, Cuernavaca, Morelos, Mexico.
- Dung DV Department of Environmental Health, Faculty of Public Health, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam.
- Forsberg B Department of Public Health and Clinical Medicine, Umeå University, Sweden.
- Goodman P Technological University Dublin (TU Dublin), Dublin, Ireland.
- Guo YL National Institute of Environmental Health Science, National Health Research Institutes, Zhunan, Taiwan.
- Guo Y Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.
- Hashizume M Department of Pediatric Infectious Diseases, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
- Honda Y Faculty of Health and Sport Sciences, University of Tsukuba, Tsukuba, Japan.
- Indermitte E Department of Family Medicine and Public Health, University of Tartu, Tartu, Estonia.
- Íñiguez C Department of Statistics and Computational Research, University of València, València, Spain.
- Kan H Department of Environmental Health, School of Public Health, Fudan University, Shanghai, China.
- Kim H Graduate School of Public Health, Seoul National University, Seoul, Republic of Korea.
- Kyselý J Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
- Lavigne E School of Epidemiology and Public Health, Faculty of Medicine, University of Ottawa, Ottawa, Canada.
- Michelozzi P Department of Epidemiology, Lazio Regional Health Service, Rome, Italy.
- Orru H Department of Family Medicine and Public Health, University of Tartu, Tartu, Estonia.
- Ortega NV Department of Public Health, Universidad de los Andes, Santiago, Chile.
- Pascal M Santé Publique France, Department of Environmental Health, French National Public Health Agency, Saint Maurice, France.
- Ragettli MS Swiss Tropical and Public Health Institute, Basel, Switzerland.
- Saldiva PHN Institute of Advanced Studies, University of São Paulo, São Paulo, Brazil.
- Schwartz J Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
- Scortichini M Air Health Science Division, Health Canada, Ottawa, Canada.
- Seposo X Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, Kyoto, Japan.
- Tobias A Institute of Environmental Assessment and Water Research (IDAEA), Spanish Council for Scientific Research (CSIC), Barcelona, Spain.
- Tong S Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
- Urban A Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
- De la Cruz Valencia C Department of Environmental Health, National Institute of Public Health, Cuernavaca, Morelos, Mexico.
- Zanobetti A Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
- Zeka A Institute for the Environment, Brunel University London, London, UK.
- Gasparrini A Department of Public Health, Environments and Society, London School of Hygiene and Tropical Medicine, London, UK.
- 2019-09-26
Published in:
- Environmental health perspectives. - 2019
English
BACKGROUND
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.
OBJECTIVES
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.
METHODS
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.
RESULTS
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.
DISCUSSION
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.
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.
OBJECTIVES
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.
METHODS
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.
RESULTS
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.
DISCUSSION
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.
- Language
-
- English
- Open access status
- gold
- Identifiers
-
- DOI 10.1289/EHP5430
- PMID 31553655
- Persistent URL
- https://sonar.ch/global/documents/203432
Statistics
Document views: 88
File downloads:
- Full-text: 0