IJE Advance Access published online on June 3, 2008
International Journal of Epidemiology, doi:10.1093/ije/dyn086
International study of temperature, heat and urban mortality: the ‘ISOTHURM’ project
1 National Centre for Epidemiology and Population Health, The Australian National University College of Medicine and Health Sciences, Canberra, Australia.
2 Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK.
3 Faculty of Public Health, Thammasat University, Pathumtani, Thailand.
4 Air Pollution Epidemiology and Research Laboratory, Institute of Public Health, Bucharest, Romania.
5 Faculty of Health Sciences, University of Cape Town Institute of Infectious Disease and Molecular Medicine, Cape Town, South Africa.
6 Research Institute for Health Sciences, Chiang Mai University, Chiang Mai, Thailand.
7 Department for Environment and Health, Institute of Public Health of the Republic of Slovenia, Ljubljana, Slovenia.
8 Departments of Epidemiology and Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI, USA.
9 Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México.
10 Comisión de Evidencia y Manejo de Riesgos (COFEPRIS), Secretaría de Salud, Mexico City, México.
11 Instituto de Saúde Coletiva, Federal University of Bahia, Salvador, Brazil.
12 Department of Preventive Medicine, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
13 National Centre of Hygiene, Medical Ecology, and Nutrition, Sofia, Bulgaria (posthumous).
* Corresponding author. Public and Environmental Health Research Unit (PEHRU), London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT. E-mail: sari.kovats{at}lshtm.ac.uk
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Abstract |
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Background This study describes heat- and cold-related mortality in 12 urban populations in low- and middle-income countries, thereby extending knowledge of how diverse populations, in non-OECD countries, respond to temperature extremes.
Methods The cities were: Delhi, Monterrey, Mexico City, Chiang Mai, Bangkok, Salvador, São Paulo, Santiago, Cape Town, Ljubljana, Bucharest and Sofia. For each city, daily mortality was examined in relation to ambient temperature using autoregressive Poisson models (2- to 5-year series) adjusted for season, relative humidity, air pollution, day of week and public holidays.
Results Most cities showed a U-shaped temperature-mortality relationship, with clear evidence of increasing death rates at colder temperatures in all cities except Ljubljana, Salvador and Delhi and with increasing heat in all cities except Chiang Mai and Cape Town. Estimates of the temperature threshold below which cold-related mortality began to increase ranged from 15°C to 29°C; the threshold for heat-related deaths ranged from 16°C to 31°C. Heat thresholds were generally higher in cities with warmer climates, while cold thresholds were unrelated to climate.
Conclusions Urban populations, in diverse geographic settings, experience increases in mortality due to both high and low temperatures. The effects of heat and cold vary depending on climate and non-climate factors such as the population disease profile and age structure. Although such populations will undergo some adaptation to increasing temperatures, many are likely to have substantial vulnerability to climate change. Additional research is needed to elucidate vulnerability within populations.
Keywords Temperature, heat, mortality, low income populations, epidemiology, cities, meteorological factors, climate
Accepted 15 April 2008