International study of temperature,heat and urban mortality: the ‘ISOTHURM’ project

Abstract

Background This study describes heat-andcold-related mortality in 12 urban populations in low- and middle-income countries,thereby extending knowledge of how diverse populations,innon-OECD countries,respond to temperature extremes.Methods The cities were:Delhi,Monterrey,MexicoCity,ChiangMai, Bangkok,Salvador,SãoPaulo,Santiago,CapeTown,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 15ºC to 29ºC;the threshold for heat-related deaths ranged from 16ºC to 31ºC. Heat thresholds were generally higher in cities with warmer climates,while cold thresholds were un related to climate.Conclusions Urban populations,in diverse geographic settings,experience in creases inmortality 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 in creasing temperatures,many are likely to have substantial vulnerability to climate change.Additional research is needed to elucidate vulnerability within populations.