Adverse heat‐health outcomes and critical environmental limits (Pennsylvania State University Human Environmental Age Thresholds project)

Abstract

Background The earth's climate is warming and the frequency, duration, and severity of heat waves are increasing. Meanwhile, the world's population is rapidly aging. Epidemiological data demonstrate exponentially greater increases in morbidity and mortality during heat waves in adults ≥65 years. Laboratory data substantiate the mechanistic underpinnings of age‐associated differences in thermoregulatory function. However, the specific combinations of environmental conditions (i.e., ambient temperature and absolute/relative humidity) above which older adults are at increased risk of heat‐related morbidity and mortality are less clear. Methods This review was conducted to (1) examine the recent (past 3 years) literature regarding heat‐related morbidity and mortality in the elderly and discuss projections of future heat‐related morbidity and mortality based on climate model data, and (2) detail the background and unique methodology of our ongoing laboratory‐based projects aimed toward identifying the specific environmental conditions that result in elevated risk of heat illness in older adults, and the implications of using the data toward the development of evidence‐based safety interventions in a continually‐warming climate (PSU HEAT; Human Environmental Age Thresholds). Results The recent literature demonstrates that extreme heat continues to be increasingly detrimental to the health of the elderly and that this is apparent across the world, although the specific environmental conditions above which older adults are at increased risk of heat‐related morbidity and mortality remain unclear. Conclusion Characterizing the environmental conditions above which risk of heat‐related illnesses increase remains critical to enact policy decisions and mitigation efforts to protect vulnerable people during extreme heat events.

Extreme climatic events and human biology and health: A primer and opportunities for future research

“…Using small, portable weather stations in field sites, like the Kestrel 5400 Heat Stress Tracker, can provide real‐time changes in ambient conditions, including temperature, relative humidity, wind speed, solar radiation, heat index, and wet bulb globe temperature to link to physiological variables being measured. The use of climate chambers is a more expensive, yet gold‐standard measure of ensuring exposures to precise climatic conditions, including both heat and humidity as well as cold. These experimental methods are providing a way to understand human environmental limits (Vecellio et al, 2022; Wolf et al, 2023) and to test biogeographical rules in relation to different climatic conditions (Maddux, Ocobock, & Cowgill, in process). Finally, the use of mapping and GIS software will help to assess differential impacts of extreme climatic events ranging from extreme flooding to hurricanes to extreme heat with respect to social disparities and environmental injustice. Mapping their spatial relation to health outcomes will demonstrate how risk differs by intersecting marginalities like low socioeconomic status and race/ethnicity (Sanders et al, 2022).…”

“…In this issue, Wolf et al (2023) provide an updated review of the literature to examine how extreme heat affects adverse‐health events and human environmental age thresholds to extreme heat. They highlight the relations between extreme heat on morbidity and mortality, including kidney failure, heart attacks, stroke, hospital admissions, circulatory and respiratory mortality, and all‐cause mortality.…”

“…This finding has large‐scale implications for human adaptability in hotter and more humid settings. They highlight experimental procedures, including heat chambers and psychometric charts to better understand these limits (Wolf et al, 2023). Further, they discuss how global demographic patterns of an aging population will play into this dilemma, as those aged 65 and over are at greatest risk of mortality from heat stress.…”

“…At what limit does heat stress increase risk of cardiovascular and kidney damage? (Pradhan et al, 2019;Wolf et al, 2023) How does extreme heat experienced in utero affect human water needs, thirst perception, and sweat gland distribution? (Best et al, 2019;Rosinger, 2020) How does extreme heat affect cognitive processes?…”

“…The use of climate chambers is a more expensive, yet gold-standard measure of ensuring exposures to precise climatic conditions, including both heat and humidity as well as cold. These experimental methods are providing a way to understand human environmental limits (Vecellio et al, 2022;Wolf et al, 2023) and to test biogeographical rules in relation to different climatic conditions (Maddux, Ocobock, & Cowgill, in process). 5.…”