Climate change and health: more research on adaptation is needed
Authors: Tao Liu, Wenjun Ma
Journal: The Lancet Planetary Health (2019)

Climate change is widely recognised as one of the biggest global threats of the 21st century. The Intergovernmental Panel on Climate Change has projected that global warming is likely to reach 1·5°C between 2030 and 2052 if climate change continues at the current rate.1The Intergrovernmental Panel on Climate ChangeSpecial Report. Global warming of 1·5°C.https://www.ipcc.ch/sr15/Date accessed: July 1, 2019Google Scholar Generally, climate change will exert adverse effects on human health. For example, many studies2Watts N Adger WN Ayeb-Karlsson S et al.The Lancet Countdown: tracking progress on health and climate change.Lancet. 2017; 389: 1151-1164Summary Full Text Full Text PDF PubMed Scopus (241) Google Scholar have found that heat-related mortality would increase in parallel with climate change. However, few studies have considered the effects of adaptation, which might lead to uncertainty in risk assessments of climate change. In The Lancet Planetary Health, Hicham Achebak and colleagues3Achebak H Devolder D Ballester J Trends in temperature-related age-specific and sex-specific mortality from cardiovascular diseases in Spain: a national time-series analysis.Lancet Planet Health. 2019; 3: e297-e306Summary Full Text Full Text PDF PubMed Scopus (70) Google Scholar did a country-wide time-series analysis in mainland Spain and the Balearic Islands to assess trends in temperature-related cardiovascular disease mortality between 1980 and 2016. This is the first study to systematically investigate the health impact of the 1°C increase in annual temperature that has been observed in Spain since 1980. The authors found that the effects of warm and cold temperatures on cardiovascular disease mortality, as assessed by relative risk (RR) and attributable fraction, differed by sex and age group; the RR and attributable fraction of cardiovascular deaths due to warm and cold temperatures decreased over the 37-year time period for both sexes and all age groups. These reductions in RR and attributable fraction of temperature-related cardiovascular disease deaths might be associated with adaptive responses and more general factors, such as socioeconomic development, improved housing conditions, use of air conditioning, and health-care service development. A key message from this study was that the increased temperatures observed in Spain since 1980 occurred in parallel with substantial adaptations to both high and low temperatures. This finding highlights the importance of considering adaptation in health risk assessments of climate change.4Achebak H Devolder D Ballester J Heat-related mortality trends under recent climate warming in Spain: a 36-year observational study.PLoS Med. 2018; 15e1002617Crossref PubMed Scopus (38) Google Scholar Human susceptibility to high temperatures and heatwaves has substantially declined in the past five decades.5Petkova EP Gasparrini A Kinney PL Heat and mortality in New York city since the beginning of the 20th century.Epidemiology. 2014; 25: 554-560Crossref PubMed Scopus (121) Google Scholar However, the temporal health effects of cold temperatures remain uncertain. For example, a multi-country analysis6Vicedocabrera AM Sera F Guo Y et al.A multi-country analysis on potential adaptive mechanisms to cold and heat in a changing climate.Environ Int. 2018; 111: 239-246Crossref PubMed Scopus (95) Google Scholar showed either an increase, a decrease, or a stable trend in the effects of cold temperatures across countries. We hypothesize that if improvements in socioeconomic development and structural transformations contributed to the decline in heat-related mortality, a similar reduction in cold-related mortality would be expected. Consistent with this hypothesis, Achebak and colleagues reported that the effects of cold temperatures on mortality significantly declined between 1980 and 2016 in Spain. These findings suggest that long-term changes in cold-attributable mortality are dependent on location and the magnitude of changes in temperature. Although many studies have assessed the risk of heat-attributable mortality in the context of global warming, several studies7Gasparrini A Guo Y Hashizume M et al.Mortality risk attributable to high and low ambient temperature: a multicountry observational study.Lancet. 2015; 386: 369-375Summary Full Text Full Text PDF PubMed Scopus (20) Google Scholar have reported that cold temperatures were responsible for most temperature-related deaths. Therefore, when considering the effects of adaptation in the health risk assessment of climate change, it is also necessary to comprehensively consider the effects of both warm and cold temperatures and estimate the net effects of temperature changes; this approach could directly indicate the extent to which an expected increase in heat-related mortality could be offset by the decrease in mortality due to cold temperatures and adaptation in different climate change scenarios.8Gasparrini A Guo Y Sera F et al.Projections of temperature-related excess mortality under climate change scenarios.Lancet Planet Health. 2017; 1: e360-e367Summary Full Text Full Text PDF PubMed Scopus (354) Google Scholar Global warming has gained much interest in the health risk assessments associated with climate change, but many knowledge gaps remain. For example, few novel technical approaches and frameworks exist that integrate the effects of adaptation in the risk assessment of climate change. On the basis of their present study, Achebak and colleagues could develop an approach that integrates the associations between temperature and mortality into the risk assessment of climate change, to further estimate the net effects of temperature and adaptation on mortality in Spain. Additionally, causal pathways and physiological acclimatisation might differ with exposure to warm temperatures compared with cold temperatures, and vary among regions.9Arbuthnott K Hajat S Heaviside C Vardoulakis S Changes in population susceptibility to heat and cold over time: assessing adaptation to climate change.Environ Health. 2016; 15: 33Crossref PubMed Scopus (96) Google Scholar Multicentre studies are needed to identify the factors that modify the effects of temperature and temporal variation in mortality, and understand the mechanisms of temporal changes that are associated with human susceptibility to warm and cold temperatures. Although many previous studies have studied mortality as a health outcome of climate change, a 2019 study10Liu T Ren Z Zhang Y et al.Modification effects of population expansion, ageing, and adaptation on heat-related mortality risks under different climate change scenarios in Gangzhou, China.Int J Environ Res Public Health. 2019; 16: 376Crossref Scopus (17) Google Scholar has suggested that years of life lost is the most appropriate measure to summarise the associations between temperature and mortality because it indicates the extent to which lives are shortened by exposure to non-optimum temperature ranges.10Liu T Ren Z Zhang Y et al.Modification effects of population expansion, ageing, and adaptation on heat-related mortality risks under different climate change scenarios in Gangzhou, China.Int J Environ Res Public Health. 2019; 16: 376Crossref Scopus (17) Google Scholar Hence, the use of years of life lost is recommended for the estimation of the burden of diseases resulting from climate change. The study by Achebak and colleagues provides valuable information for policy makers and researchers for the development of strategies that enable adaption to the adverse health impacts of climate change. However, the study only included Spain. Studies that include more countries and time-series data for longer time periods are needed to further investigate the temporal trends in temperature-related mortality, especially regarding the effects of cold temperatures on mortality. We declare no competing interests. Trends in temperature-related age-specific and sex-specific mortality from cardiovascular diseases in Spain: a national time-series analysisIn Spain, the observed warming of the climate has occurred in parallel with substantial adaptation to both high and low temperatures. The reduction in the RR and the attributable fraction associated with heat would be compatible with an adaptive response specifically addressing the negative consequences of climate change. Nevertheless, the simultaneous reduction in the RR and attributable fraction of cold temperatures also highlights the importance of more general factors such as socioeconomic development, increased life expectancy and quality, and improved health-care services in the country. Full-Text PDF Open Access