Folkerts Mireille A, Bröde Peter, Botzen W J Wouter, Martinius Mike L, Gerrett Nicola, Harmsen Carel N, Daanen Hein A M
Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, Netherlands.
Leibniz Research Centre for Working Environment and Human Factors (IfADo), Dortmund, Germany.
Front Physiol. 2020 Mar 18;11:225. doi: 10.3389/fphys.2020.00225. eCollection 2020.
It is essentially unknown how humans adapt or will adapt to heat stress caused by climate change over a long-term interval. A possible indicator of adaptation may be the minimum mortality temperature (MMT), which is defined as the mean daily temperature at which the lowest mortality occurs. Another possible indicator may be the heat sensitivity, i.e., the percentage change in mortality per 1°C above the MMT threshold, or heat attributable fraction (AF), i.e., the percentage relative excess mortality above MMT. We estimated MMT and heat sensitivity/AF over a period of 23 years for older adults (≥65 years) in the Netherlands using three commonly used methods. These methods are segmented Poisson regression (SEG), constrained segmented distributed lag models (CSDL), and distributed lag non-linear models (DLNM). The mean ambient temperature increased by 0.03°C/year over the 23 year period. The calculated mean MMT over the 23-year period differed considerably between methods [16.4 ± 1.2°C (SE) (SEG), 18.9 ± 0.5°C (CSDL), and 15.3 ± 0.4°C DLNM]. MMT increased during the observed period according to CSDL (0.11 ± 0.05°C/year) and DLNM (0.15 ± 0.02°C/year), but not with SEG. The heat sensitivity, however, decreased for the latter method (0.06%/°C/year) and did not change for CSDL. Heat AF was calculated for the DLNM method and decreased with 0.07%/year. Based on these results we conclude that the susceptibility of humans to heat decreases over time, regardless which method was used, because human adaptation is shown by either an increase in MMT (CSDL and DLNM) or a decrease in heat sensitivity for unchanged MMT (SEG). Future studies should focus on what factors (e.g., physiological, behavioral, technological, or infrastructural adaptations) influence human adaptation the most, so it can be promoted through adaptation policies. Furthermore, future studies should keep in mind that the employed method influences the calculated MMT, which hampers comparability between studies.
从本质上讲，人类如何适应或将会如何适应气候变化在长期内所造成的热应激尚不清楚。适应的一个可能指标或许是最低死亡率温度（MMT），它被定义为出现最低死亡率时的日平均温度。另一个可能指标或许是热敏感性，即高于MMT阈值每升高1°C时死亡率的百分比变化，或者是热归因分数（AF），即高于MMT的相对超额死亡率百分比。我们使用三种常用方法估算了荷兰老年人（≥65岁）在23年期间的MMT以及热敏感性/AF。这些方法分别是分段泊松回归（SEG）、约束分段分布滞后模型（CSDL）和分布滞后非线性模型（DLNM）。在这23年期间，平均环境温度每年升高0.03°C。三种方法计算出的23年期间的平均MMT差异很大[16.4±1.2°C（标准误）（SEG）、18.9±0.5°C（CSDL）和15.3±0.4°C（DLNM）]。根据CSDL（0.11±0.05°C/年）和DLNM（0.15±0.02°C/年），MMT在观测期内有所升高，但SEG方法未显示出升高。然而，对于后一种方法热敏感性降低了（0.06%/°C/年），而CSDL方法的热敏感性没有变化。我们针对DLNM方法计算了热AF，其以每年0.07%的速度下降。基于这些结果我们得出结论，无论使用哪种方法，人类对热的易感性都会随着时间降低，因为人类适应表现为MMT升高（CSDL和DLNM）或者在MMT不变时热敏感性降低（SEG）。未来的研究应聚焦于哪些因素（例如生理、行为、技术或基础设施适应）对人类适应影响最大，以便能够通过适应政策加以促进。此外，未来的研究应牢记所采用的方法会影响计算出的MMT，这会妨碍不同研究之间的可比性。
