Shifts in the seasonal distribution of deaths in Australia, 1968–2007
- 529 Downloads
Studies in temperate countries have shown that both hot weather in summer and cold weather in winter increase short-term (daily) mortality. The gradual warming, decade on decade, that Australia has experienced since the 1960s, might therefore be expected to have differentially affected mortality in the two seasons, and thus indicate an early impact of climate change on human health. Failure to detect such a signal would challenge the widespread assumption that the effect of weather on mortality implies a similar effect of a change from the present to projected future climate. We examine the ratio of summer to winter deaths against a background of rising average annual temperatures over four decades: the ratio has increased from 0.71 to 0.86 since 1968. The same trend, albeit of varying strength, is evident in all states of Australia, in four age groups (aged 55 years and above) and in both sexes. Analysis of cause-specific mortality suggests that the change has so far been driven more by reduced winter mortality than by increased summer mortality. Furthermore, comparisons of this seasonal mortality ratio calculated in the warmest subsets of seasons in each decade, with that calculated in the coldest seasons, show that particularly warm annual conditions, which mimic the expected temperatures of future climate change, increase the likelihood of higher ratios (approaching 1:1). Overall, our results indicate that gradual climate change, as well as short-term weather variations, affect patterns of mortality.
KeywordsTemperature Mortality Climate change Season Poisson modelling Mortality ratio
C.M.B. and A.J.M. were supported by National Health and Medical Research Council Australia Fellowship 0418141. This work was also supported by National Health and Medical Research Council Project Grant 585408.
- Analitis A, Katsouyanni K, Biggeri A, Baccini M, Forsberg B, Bisanti L, Kirchmayer U, Ballester F, Cadum E, Goodman P, Hojs A, Sunyer J, Tittanen P, Michelozzi P (2008) Effects of cold weather on mortality: results from 15 European Cities Within the PHEWE Project. Am J Epidemiol 168:1397–1408CrossRefGoogle Scholar
- Bambrick H, Dear K, Woodruff R, Hanigan I, McMichael A (2008) The impacts of climate change on three health outcomes: temperature-related mortality and hospitalisations, salmonellosis and other bacterial gastroenteritis, and population at risk from dengue. Garnaut Climate Change Review, CanberraGoogle Scholar
- Bureau of Meteorology, CSIRO (2010) State of the Climate. Australian Government Bureau of Meteorology & Commonwealth Scientific and Industrial Research Organisation, MelbourneGoogle Scholar
- Cameron AS, Roder DM, Esterman AJ, Moore BW (1985) Mortality from influenza and allied infections in South Australia during 1968–1981. Med J Aust 142:14–17Google Scholar
- CSIRO and Bureau of Meterology (2007) Climate change in Australia: Technical Report 2007. Melbourne: CSIRO, BoM. http://www.climatechangeinaustralia.gov.au.
- Davis RE, Knappenberger PC, Novicoff WM, Michaels PJ (2003b) Decadal changes in summer mortality in US cities. Int J Biometeorol 47:166–175Google Scholar
- McMichael AJ, Wilkinson P, Kovats RS, Pattenden S, Hajat S, Armstrong B, Vajanapoom N, Niciu EM, Mahomed H, Kingkeow C, Kosnik M, O’Neill MS, Romieu I, Ramirez-Aguilar M, Barreto ML, Gouveia N, Nikiforov B (2008) International study of temperature, heat and urban mortality: the ‘ISOTHURM’ project. Int J Epidemiol 37:1121–1131CrossRefGoogle Scholar
- McMichael AJ, Woodruff RE, Whetton P, Hennessy K, Nicholls N, Hales S, Woodward A, Kjellstrom T (2003) Human health and climate change in Oceania: a risk assessment 2002. Commonwealth Department of Health and Ageing, CanberraGoogle Scholar