ORIGINAL ARTICLE Extremely cold and hot temperatures increase the risk of ischaemic heart disease mortality: epidemiological evidence from China Yuming Guo, 1,2 Shanshan Li, 3 Yanshen Zhang, 4 Ben Armstrong, 5 Jouni J K Jaakkola, 6 Shilu Tong, 7 Xiaochuan Pan 1 ▸ Additional supplementary files are published online only. To view these files please visit the journal online (http://dx.doi. org/10.1136/heartjnl-2012- 302518). 1 Department of Occupational and Environmental Health, School of Public Health, Peking University, Beijing, China 2 School of Medicine, The University of Queensland, Brisbane, Australia 3 Department of Epidemiology and Biostatistics, School of Population Health, The University of Queensland, Brisbane, Australia 4 Center for Environmental Risk and Damage Assessment, Chinese Academy for Environmental Planning, Beijing, China 5 Department of Social and Environmental Health Research, London School of Hygiene & Tropical Medicine, London, UK 6 Center for Environmental and Respiratory Health Research, Institute of Health Sciences, University of Oulu, Oulu, Finland 7 School of Public Health and Social Work and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia Correspondence to: Dr Yuming Guo, School of Medicine, The University of Queensland, Brisbane, QLD 4006, Australia; guoyuming@yahoo.cn Professor Xiaochuan Pan, Department of Occupational and Environmental Health, School of Public Health, Peking University, Beijing 100191, China; xcpan@hsc.pku.edu.au Accepted 6 October 2012 ABSTRACT Objective To examine the effects of extremely cold and hot temperatures on ischaemic heart disease (IHD) mortality in five cities (Beijing, Tianjin, Shanghai, Wuhan and Guangzhou) in China; and to examine the time relationships between cold and hot temperatures and IHD mortality for each city. Design A negative binomial regression model combined with a distributed lag non-linear model was used to examine city-specific temperature effects on IHD mortality up to 20 lag days. A meta-analysis was used to pool the cold effects and hot effects across the five cities. Patients 16 559 IHD deaths were monitored by a sentinel surveillance system in five cities during 2004–2008. Results The relationships between temperature and IHD mortality were non-linear in all five cities. The minimum- mortality temperatures in northern cities were lower than in southern cities. In Beijing, Tianjin and Guangzhou, the effects of extremely cold temperatures were delayed, while Shanghai and Wuhan had immediate cold effects. The effects of extremely hot temperatures appeared immediately in all the cities except Wuhan. Meta-analysis showed that IHD mortality increased 48% at the 1st percentile of temperature (extremely cold temperature) compared with the 10th percentile, while IHD mortality increased 18% at the 99th percentile of temperature (extremely hot temperature) compared with the 90th percentile. Conclusions Results indicate that both extremely cold and hot temperatures increase IHD mortality in China. Each city has its characteristics of heat effects on IHD mortality. The policy for response to climate change should consider local climate–IHD mortality relationships. INTRODUCTION Extremely cold and hot temperatures are natural hazards for the human body. The adverse effects of extremely cold and hot temperatures may vary according to climatic types and population charac- teristics, because people may acclimatise to their local environmental conditions, through adaptation in physiology, behaviour and culture. 1 The health impacts of extreme temperatures are likely to depend on local conditions, and may be modified by social, economic and demographic factors, and characteristics of infrastructure. 2 Other factors such as income, education, social isolation, inten- sity of urban heat islands, housing characteristics, access to air conditioning and availability of health- care services can also modify the effects of extreme temperatures on human health. 34 Therefore, there is a need to assess the effect of extreme tempera- tures on health in different regions. Previous studies have provided evidence that extremely cold and hot temperatures have negative impacts on vulnerable people. 5–7 The elderly and children are more vulnerable to extreme tempera- tures than youth. 89 People with particular diseases such as cardiovascular and respiratory diseases, dia- betes, chronic mental disorders or other pre- existing medical conditions are more susceptible to the health effects of extreme temperatures than healthy people. 10–12 Ischaemic heart disease (IHD) is the leading cause of death worldwide 13 and the incidence is increasing in China. 14 IHD was ranked fifth for the causes of disability adjusted life years worldwide in 1990, and is projected be ranked first in 2020. 15 Previous studies indicate a seasonal trend in IHD mortality, with the highest rate in winter. 16 17 Studies have examined the effects of temperature on IHD mortality, 18–20 but few studies have assessed the lag effects of heat on IHD mortality, especially in China. Developing countries are anticipated to be sus- ceptible to the impact of extreme temperatures, because they have more limited adaptive capacity and more vulnerable people than developed coun- tries. 1 People have the ability to adapt to their local climates, through physiological, behavioural and cultural adaptation. So we need to consider human capacity to adapt to varied climates and environments. In China, only a few studies have examined the impact of temperature on non- accidental, cardiovascular and respiratory mortality in Shanghai, 21 22 Beijing 23 and Tianjin. 24 To date, no study has examined the impact of extreme tem- peratures on IHD death in multiple cities in China. In this study, we aimed to assess the regional char- acteristics of the associations between ambient tem- perature and IHD mortality in five cites (Beijing, Tianjin, Shanghai, Wuhan and Guangzhou, from north to south) in China ( figure 1); and to examine the lag effects of extremely cold and hot tempera- tures on IHD mortality for each city. METHODS Data collection We collected data from five cities (Beijing, Tianjin, Shanghai, Wuhan and Guangzhou) in China ( figure 1). Beijing and Tianjin are located in Heart 2012;0:1–9. doi:10.1136/heartjnl-2012-302518 1 Epidemiology Heart Online First, published on November 13, 2012 as 10.1136/heartjnl-2012-302518 Copyright Article author (or their employer) 2012. Produced by BMJ Publishing Group Ltd (& BCS) under licence. group.bmj.com on November 13, 2012 - Published by heart.bmj.com Downloaded from