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Background: As climate change, compound hot extremes (CHEs), daytime and nighttime persistent hot extremes, are projected to become much more frequent and intense, which may pose a serious threat to human health. However, evidence on the impact of CHEs on injury is rare., Methods: We collected injury death data and daily meteorological data from six Chinese provinces during 2013-2018. A time-stratified case-crossover design with two-stage analytic approach was applied to assess the associations of CHEs with injury mortality by intention, mechanism, age and gender. Using the projected daily temperatures of five General Circulation Models (GCMs), we projected the frequency of CHEs and CHEs-attributable mortality burden of injury under three Representative Concentration Pathway (RCP) scenarios., Results: CHEs were significantly associated with increased injury mortality risk (RR = 1.14, 95%CI: 1.09-1.19), with strong effects on unintentional injuries (RR = 1.16, 95%CI:1.11,1.22) and intentional injuries (RR = 1.11, 95%CI:0.99,1.25). Female (RR = 1.21,95%CI: 1.13-1.29) and the elderly (RR = 1.30, 95%CI: 1.22-1.39) were more susceptible to CHEs. Both the frequency and injury mortality burden of CHEs showed a steep rising trend under RCP8.5 scenario, with a 7.37-fold and 8.22-fold increase respectively, by the end of the century, especially in southern, eastern, central and northwestern China., Conclusion: CHEs were associated with increased injury mortality risk, and the CHEs-attributable injury mortality burden was projected to aggravate substantially in the future as global warming. It is urgent to develop targeted adaptation policies to alleviate the health burden of CHEs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Compound day-night heat waves (CohotEs) have more adverse effects on human health and ecosystem, and the consequences vary with humidity. This study classifies the CohotEs over Chinese mainland into wet and dry CohotEs, and compares their characteristics and associated circulation anomalies. Here, a populated region of mid-eastern China (MEC) with higher occurrence of both types of CohotEs is mainly focused. Results show that, during past six decades, wet CohotEs have higher frequency, longer duration and broader spatial scale, while dry CohotEs are less, shorter and more regional. Both types of CohotEs are associated with anticyclonic anomalies accompanied by the strengthening and northwestern expansion of western Pacific subtropical high (WPSH), leading to adiabatic heating with anomalous subsidence. The anomalies in wet CohotEs are influenced by the eastward expansion of East Asian westerly jet stream and northeastward expansion of the south Asia high. Anomalous southwesterlies transport additional water vapor from the tropics, leading to above-normal humidity that could reduce the amplitudes of anomalous subsidence but favor heat maintenance. By contrast, dry CohotEs are related to a more stable barotropic anticyclonic structure, and the anomalous signals are stronger in the middle-lower troposphere. Meanwhile, tropical cyclones appear over the South China Sea below 500 hPa, promoting the intensification of northwestward shifts of WPSH and anomalous northeasterlies over South China. So, lower humidity results from weakened northward water vapor transport could lead to faster heat dissipation and thus shorter duration for dry CohotEs. Our results emphasize the diversity of CohotEs, indicating that different types of CohotEs should be analyzed separately and multiple local and large-scale circulations need to be considered for better forecasts and predictions of CohotEs. • Characteristics of wet and dry compound hot extremes (CohotEs) are analyzed. • Circulation anomalies of wet and dry CohotEs are compared over mid-eastern China. • Anomalous anticyclone and western Pacific subtropical high (WPSH) cause CohotEs. • Wet CohotEs are influenced by eastward (westward) shifts of south Asia high (WPSH). • Dry CohotEs are related to shifts of WPSH and tropic cyclonic anomaly. [ABSTRACT FROM AUTHOR]