Projection of Temperature-Related Myocardial Infarction in Augsburg, Germany
Moving on from the Paris Agreement on Climate Change
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Background: Substantial efforts are required to limit global warming to under 2 °C, with 1.5 °C as the target (Paris Agreement goal). We set out to project future temperature-related myocardial infarction (MI) events in Augsburg, Germany, at increases in warming of 1.5 °C, 2 °C, and 3 °C.
Methods: Using daily time series of MI cases and temperature projections under two climate scenarios, we projected changes in temperature-related MIs at different increases in warming, assuming no changes in population structure or level of adaptation.
Results: In a low-emission scenario that limits warming to below 2 °C throughout the 21st century, temperature-related MI cases will decrease slightly by –6 (confidence interval −60; 50) per decade at 1.5 °C of warming. In a high-emission scenario going beyond the Paris Agreement goals, temperature-related MI cases will increase by 18 (−64; 117) and 63 (−83; 257) per decade with warming of 2 °C and 3 °C, respectively.
Conclusion: The future burden of temperature-related MI events in Augsburg at 2 °C and 3 °C of warming will be greater than at 1.5 °C. Fulfilling the Paris Agreement goal of limiting global warming to no more than 1.5 °C is therefore essential to avoid additional MI events due to climate change.
Climate change is the biggest global health threat, and tackling it could be the greatest global health opportunity of the 21st century (1). To reduce the health risks of climate change, in 2015 the United Nations Framework Convention on Climate Change (UNFCCC) adopted the Paris Agreement, which aims at holding global warming to well below 2 °C above pre-industrial levels and pursuing efforts to limit it to 1.5 °C (2). However, little is known about the difference in health impacts between the 1.5 °C and 2 °C warming targets (3, 4). Although emerging evidence from regional, national, and global studies shows a potential increase in temperature-related mortality as a result of climate change (5–9), nearly all these studies have focused on a certain future period but not on a specific warming target (3). Thus, it remains unclear whether limiting global warming to 1.5 °C instead of 2 °C will avoid temperature-related health impacts (3, 10).
In October 2018, the Intergovernmental Panel on Climate Change (IPCC) issued a Special Report on the impacts of global warming of 1.5 °C (SR15) and concluded with very high confidence that heat-related health impacts will be greater at 2 °C of warming than at 1.5 °C (11). However, cold-related mortality is projected to decrease with warming winters in some regions (11), and it remains unclear to which extent heat-related impacts may offset this decrease, leading to an uncertain overall impact of temperature on health (12). Moreover, most of the previous projection studies have focused on mortality rather than morbidity (13), leading to limited evidence regarding climate change impacts on heat-related morbidity. Cold exposure has been reported as a trigger of MI events (14), and a recent study of ours found that heat exposure is also a potential trigger (15). Plausible pathophysiological mechanisms are shown in Figure 1. In the study described here, we aimed to project future temperature-related myocardial infarction (MI) events in Augsburg, Germany, at levels of warming consistent with the Paris Agreement goals (1.5 °C and 2 °C) and higher (3 °C). This information may help health professionals and policy makers to better understand the potential health threat of climate change.
We used data from the population-based Cooperative Health Research in the Region of Augsburg (KORA) MI registry. The study area comprises the city of Augsburg and the two adjacent counties (Augsburg and Aichach-Friedberg). All recorded cases of MI and coronary deaths among residents aged 25 to 74 years (about 400,000 inhabitants) from 1 January 2001, to 31 December 2014 were included in analysis. We also evaluated subtypes of MI events, including ST-segment elevation MI (STEMI) and non-ST segment elevation MI (NSTEMI). Details of this registry are given in the eMethods. This study was approved by the ethics committee of the Bavarian Chamber of Physicians and performed in accordance with the Declaration of Helsinki.
We obtained daily mean temperatures for the period 2010 to 2099 from four global climate models under the Inter-Sectoral Impact Model Intercomparison Project Phase 2b (ISIMIP2b) (16). We used two climate change scenarios under the Representative Concentration Pathway (RCP), RCP2.6 and RCP8.5, corresponding to low and high warming and emissions, respectively (Box 2). We applied the method described in Ebi et al. (2018) (3) to determine the decade in which 1.5 °C, 2 °C, and 3 °C of warming above pre-industrial levels will be reached, using the decade 2010 to 2019 as baseline (eMethods).
Health impact assessment
We estimated the number and fraction of MI cases attributable to heat, cold, and net change (the summed impacts of heat and cold) for different levels of warming based on the assumption of no changes in population structure or level of adaptation, using a recently developed approach (17). Briefly, we used the previously estimated exposure–response functions between daily mean temperature and daily MI events (eFigure 1) (15), the temperature projections, and baseline MI cases to calculate the daily attributable number of MI events. The baseline MI cases were calculated as the average observed number of cases for each day of the year during the period 2001 to 2014. Finally, we computed the future changes as the differences between the future decades in which different levels of warming will be reached and the baseline period for each RCP. We used Monte Carlo simulations to estimate empirical confidence intervals (eCI) to address the uncertainty in exposure–response functions and the variability across global climate models. Key elements in the assessment are provided in the eBox. Details of the health impact assessment can be found in the eMethods.
Figure 2 shows the 10-year moving global mean temperature projections from the average of four global climate models in two RCP scenarios relative to pre-industrial levels. Global mean temperature in RCP8.5 exceeds 3 °C relative to pre-industrial levels by the end of the 21st century, whereas it remains below 2 °C in RCP2.6. Thus, we used RCP2.6 for the scenario fulfilling the Paris Agreement goal of 1.5 °C and RCP8.5 for warming of 2 °C and 3 °C. Based on these scenarios, warming of 1.5 °C will be reached around 2031 (Table 1). Warming of 2 °C and 3 °C will be reached around 2037 and 2052, respectively.
From 2001 to 2014, there were on average 967 coronary events per year, of which 235 were STEMI and 331 were NSTEMI. Relative to the baseline period, heat-related MIs will increase in all warming scenarios, whereas cold-related MIs will decrease (Table 2). If the Paris Agreement target of limiting warming to 1.5 °C is met, temperature-related MI cases per decade in Augsburg will decrease slightly overall (–6 [−60; 50]). Warming of 2 °C yields larger increases in heat-related MIs than reductions in cold-related MIs, leading to a net increase of 18 [−64; 117] MI cases per decade. At 3 °C of warming, beyond the Paris Agreement target, temperature-related MIs are projected to increase by 63 [−83; 257] per decade, which corresponds to an increase of about 0.7% in the burden of MI events.
Figure 3 summarizes the net changes in temperature-related MIs in the different warming scenarios overall and for the subtypes of MI. Total and NSTEMI events are generally projected to increase with increasing level of warming. Conversely, STEMI events are projected to decrease because the decrease in cold-related cases will exceed the rise in heat-related events. Most of the increased temperature-related MIs will be NSTEMI events, with the increase ranging from 21 [−13: 63] at 1.5 °C of warming to 102 [21; 201] at 3 °C of warming.
Our analyses show that all of our projected increases in global warming will increase heat-related MIs but reduce cold-related MIs in Augsburg, Germany. Holding warming to 1.5 °C instead of 2 °C or 3 °C will avoid a substantial number of temperature-related MIs. In the low-emission scenario RCP2.6, warming will be kept below 2 °C right up to 2100, resulting in a negligible net change in the number of MIs. In contrast, warming will exceed 3 °C by 2100 in the high-emission scenario RCP8.5, leading to a considerable increase in the burden of MIs.
Very few studies have directly estimated the regional health impacts of stabilizing climate warming at 1.5 °C instead of 2 °C (3). Our finding of greater heat-related impacts for warming at 2 °C than at 1.5 °C is consistent with the conclusion of IPCC Special Report 15 (11) and the findings of two recent multicenter European studies (10, 12). We also found a much lower total number of heat-related total MIs at 2 °C than at 3 °C in Augsburg for the high-emission scenario RCP8.5. A recent worldwide study found a net increase in temperature-related mortality in central and southern European cities (12), suggesting that emission reductions in line with the Paris Agreement goals can avoid heat-related impacts on MI burden.
The climate scenario RCP2.6 meets the Paris Agreement target of keeping warming well below 2 °C (Figure 1, Table 1), confirming a previous review (3), and yields a negligible change (−0.1%) in MI burden if warming is limited to 1.5 °C. In comparison, temperature-related MIs in scenario RCP8.5 will increase by 0.2% at 2 °C of warming and by 0.7% at 3 °C of warming (Table 2). Similarly, a previous study also estimated a much smaller temperature-related mortality burden for RCP2.6 than for RCP8.5 in central and southern European cities over the course of the 21st century (5).
According to the Federal Statistical Office, 135 218 MI events occurred in patients aged between 25 and 74 years in Germany in 2015 (including both acute MI and deaths from cardiac arrest) (18). Assuming our projected changes in attributable fractions in the Augsburg region could be applied to the whole of Germany, a rough calculation shows that holding warming at 1.5 °C, compared with 3 °C, would prevent 1 082 MI cases each year. This is likely to be an underestimate, as we only considered patients aged below 75, whereas the elderly have been demonstrated to be more vulnerable to heat-related mortality and morbidity (19, 20). Our findings suggest that ambitious greenhouse gas emission reductions are required to achieve the Paris Agreement targets and to prevent adverse temperature-related health impacts.
Implications for healthcare professionals
Healthcare professionals have vital roles in accelerating progress to tackle climate change. They are trained to educate patients about health threats, may be trusted more than environmentalists, and can better communicate the health risks posed by climate change and thus potentially also convince politicians that emissions of greenhouse gases must be reduced (1, 21). With the ability to effectively highlight the associated health threats, healthcare professionals should be at the forefront of the battle against climate change (22). To encourage primary care physicians and other health professionals to lead on tackling climate change, it is important to understand how climate change can impact health outcomes (23). The results of this study suggests that global warming higher than 1.5 °C will lead to increasing temperature-related MI cases. We therefore appeal to healthcare professionals to inform the public and policymakers about the potential health threats of climate change and the benefits of climate protection measures.
Strengths and limitations
To the best of our knowledge, this is the first study project the effects on heat-related MIs of global temperature increases below and above the goals set by the Paris Agreement. Our estimates are based on a validated, complete, and detailed registration of all MIs and coronary deaths in Augsburg, in combination with an established advanced approach to account for uncertainty in exposure–response functions and variability across climate models (5). Our estimates can be interpreted as the changes in heat-related MI events if the current Augsburg population were exposed to future temperatures resulting from global warming of 1.5 °C, 2 °C, and 3 °C. Thus, our projections allow isolation of the effects of a changing climate from other factors such as demographic change and population adaptation (5).
Our study has several limitations. First, our projections of the health impacts focus on specific Paris Agreement targets rather than consistent future periods. This approach uses different periods for different warming targets, which limits our ability to consider impacts of future population changes such as size, age structure, lifestyle, and underlying MI rates. As we expect more NSTEMI events but fewer STEMI events in Augsburg in the future (15), the future changes in total temperature-related MI burden may be underestimated. Moreover, the temperature projections we used have a relatively coarse spatial resolution (~ 50 km). Future studies using higher resolution temperature projections, such as those from COSMO-CLM developed by the German Weather Service (Deutscher Wetterdienst), are needed to enable estimation of the regional health impact of climate change. Furthermore, we did not consider population adaptation to heat (24). However, heat-related vulnerability may further increase in Augsburg (15), resulting in increased future temperature-related impacts.
The higher the increase in global temperature (1.5 °C, 2 °C, or 3 °C), the greater will be the burden of temperature-related MIs in Augsburg, Germany. Compared with inaction on climate change in a high-emission scenario, limiting global warming to 1.5 °C in a low-emission scenario will avoid additional MI events, suggesting that climate change mitigation policies are needed to fulfill the Paris Agreement goal of 1.5 °C.
Kai Chen PhD acknowledges support from the Alexander von Humboldt Foundation for the Humboldt Research Fellowship. The KORA research platform was initiated and financed by the Helmholtz Zentrum München, German Research Center for Environmental Health, which is funded by the German Federal Ministry of Education, Science, Research, and Technology and by the state of Bavaria. Since 2000, the MI data collection has been co-financed by the German Federal Ministry of Health and Social Security to provide population-based MI morbidity data for the official German Health Report (see www.gbe-bund.de).
Conflict of interest statement
The authors declare that no conflict of interest exists.
Manuscript received on 5 March 2019, revised version accepted on 17 June 2019
Kai Chen PhD
Helmholtz Zentrum München
Deutsches Forschungszentrum für Gesundheit und Umwelt
Institut für Epidemiologie
Ingolstädter Landstr. 1, Neuherberg
85764 München, Germany
Cite this as:
Chen K, Breitner S, Wolf K, Rai M, Meisinger C, Heier M, Kuch B, Peters A, Schneider A; on behalf of the KORA Study Group: Projection of temperature-related myocardial infarction in Augsburg, Germany: moving on from the Paris Agreement on Climate Change.
Dtsch Arztebl Int 2019; 116: 521–7. DOI: 10.3238/arztebl.2019.0521
eFigure, eBox, eMethods:
Institute for Medical Information Processing, Biometry and Epidemiology, Ludwig-Maximilians-Universität München, Munich: Dr. Susanne Breitner, Prof. Annette Peters
Ludwig-Maximilians-Universität München, Chair of Epidemiology at UNIKA-T, University of Augsburg;
Independent Research Group Clinical Epidemiology, Helmholtz Zentrum München–German Research Center for Environmental Health, Munich;
MONICA/KORA Myocardial Infarction Registry, University Hospital of Augsburg:
Prof. Christa Meisinger
KORA Study Center, University Hospital of Augsburg: Dr. Margit Heier
Department of Internal Medicine I – Cardiology, University Hospital of Augsburg; Department of Internal Medicine/Cardiology, Nördlingen Hospital, Nördlingen: Prof. Bernhard Kuch
German Research Center for Cardiovascular Research (DZHK), Partner-Site Munich:
Prof. Annette Peters
The KORA-Study Group consists of A. Peters (spokesperson), H. Schulz, L. Schwettmann, R. Leidl, M. Heier, K. Strauch, and their co-workers, who are responsible for the design and conduct of the KORA studies.
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