Impact of low-intensity heat events on mortality and morbidity in regions with hot, humid summers: a scoping literature review

Abstract

The objective of this study is to determine the impacts of low-intensity heat on human health in regions with hot, humid summers. Current literature has highlighted an increase in mortality and morbidity rates during significant heat events. While the impacts on high-intensity events are established, the impacts on low-intensity events, particularly in regions with hot, humid summers, are less clear. A scoping review was conducted searching three databases (PubMed, EMBASE, Web of Science) using key terms based on the inclusion criteria. We included papers that investigated the direct human health impacts of low-intensity heat events (single day or heatwaves) in regions with hot, humid summers in middle- and high-income countries. We excluded papers written in languages other than English. Of the 600 publications identified, 33 met the inclusion criteria. Findings suggest that low-intensity heatwaves can increase all-cause non-accidental, cardiovascular-, respiratory- and diabetes-related mortality, in regions experiencing hot, humid summers. Impacts of low-intensity heatwaves on morbidity are less clear, with research predominantly focusing on hospitalisation rates with a range of outcomes. Few studies investigating the impact of low-intensity heat events on emergency department presentations and ambulance dispatches were found. However, the data from a limited number of studies suggest that both of these outcome measures increase during low-intensity heat events. Low-intensity heat events may increase mortality. There is insufficient evidence of a causal effect of low-intensity heat events on increasing morbidity for a firm conclusion. Further research on the impact of low-intensity heat on morbidity and mortality using consistent parameters is warranted.

Heatwaves in Mozambique 1983 – 2016: Characteristics, Trends and City-Level Summaries Using High-Resolution Chirts-Daily

“…Heat-related impacts may already be observed at lower temperature thresholds than at the 90th percentile. This may be the case in tropical regions due to high humidity levels, or in vulnerable regions where people and systems have low capacity to cope with extreme heat (Gasparrini et al, 2015;Pasquini et al, 2020;Strathearn et al, 2022). However, CHIRTS-daily is currently only available until 2016 and therefore not usable in the context for monitoring or early warnings of heatwaves.…”

“…First, despite the advantages related to the heatwave definitions employed, humidity is not included in those. Humidity may play an important role in amplifying health impacts even at lower temperature thresholds than what would be considered climatologically extreme (Gasparrini et al, 2015;Pasquini et al, 2020;Strathearn et al, 2022). This is mainly of importance for the tropical regions of Mozambique, mostly in the north of the country.…”

Groundwater in terrestrial systems modelling: a new climatology of extreme heat events in Europe

“…Note that the use of terms "heat event" and "heat wave" is similar in the context of this paper, with "heat event" referring to a series of unusually hot days. Furthermore, low-intensity heat events are also mentioned in literature as either a single-day or a multi-day event over a temperature threshold between the 85 and 92.5th percentile (Strathearn et al, 2022). In addition, some authors classify heat waves as low-intensity, severe, and extreme (Nairn and Fawcett, 2014).…”

Intestinal microflora promotes Th2-mediated immunity through NLRP3 in damp and heat environments

“…Most tropical and subtropical areas experience long summers and short winters with extended periods of sunshine. Studies have found that the incidence of respiratory, cardiovascular and renal diseases, as well as mortality in patients with cardiovascular disease ( 2 ), were closely related to low-intensity heatwaves in tropical and subtropical humid areas ( 3 ). The Lingnan region of China, located in the east Asian monsoon region, is characterized by a subtropical monsoon oceanic climate.…”