Kidney injury risk during prolonged exposure to current and projected wet bulb temperatures occurring during extreme heat events in healthy young men

Abstract

Wet bulb temperatures (Twet) during extreme heat events are commonly 31°C. Recent predictions indicate that Twet will approach or exceed 34°C. Epidemiological data indicate that exposure to extreme heat events increases kidney injury risk. We tested the hypothesis that kidney injury risk is elevated to a greater extent during prolonged exposure to Twet=34°C compared to Twet=31°C. Fifteen healthy men rested for eight hours in Twet=31 (0)°C and Twet=34 (0)°C. Insulin-like growth factor-binding protein 7 [IGFBP7], tissue inhibitor of metalloproteinase 2 [TIMP-2], and thioredoxin 1 (TRX-1) were measured from urine samples. The primary outcome was the product of IGFBP7 and TIMP-2 [IGFBP7·TIMP-2], which provided an index of kidney injury risk. Plasma interleukin-17a (IL-17a) was also measured. Data are presented at pre and after eight hours of exposure, and as mean (SD) change from preexposure. The increase in [IGFBP7·TIMP-2] was markedly greater at eight hours in the 34°C (+26.9 (27.1) [ng/mL]2/1000) compared to the 31°C (+6.2 (6.5) [ng/mL]2/1000) trial (p<0.01). Urine TRX-1, a marker of renal oxidative stress, was higher at eight hours in the 34°C (+77.6 (47.5) ng/min) compared to the 31°C (+16.2 (25.1) ng/min) trial (p<0.01). Plasma IL-17a, an inflammatory marker, was elevated at eight hours in the 34°C (+199.3 (90.0) fg/dL; p<0.01) compared to the 31°C (+9.0 (95.7) fg/dL) trial. Kidney injury risk is exacerbated during prolonged resting exposures to Twet experienced during future extreme heat events (34°C) compared to that experienced currently (31°C), likely due to oxidative stress and inflammatory processes.

Shifting focus: Time to look beyond the classic physiological adaptations associated with human heat acclimation

“…This phenomenon is exacerbated by mild dehydration/hypohydration (2.5% of body mass) in healthy young males and females (Chapman et al., 2023 , 2020 ). This portrait is supported by studies showing an increased AKI prevalence during active heat stress in occupational (Moyce et al., 2016 ; Schlader et al., 2017 ; Schrier et al., 1970 ) and sports (Divine et al., 2018 ; Hodgson et al., 2017 ) settings, but also an increased risk of kidney injury during prolonged passive heat stress in healthy young males (8 h, 32–35°C, 95% humidity) (Hess et al., 2022 ). Thermal and cardiovascular adaptations inherent to heat acclimation, namely, improved body fluid regulation, expanded plasma volume, increased sodium reabsorption, and lowered core temperature during heat stress, suggest that heat acclimation may preserve kidney function and reduce the risk of AKI associated with heat stress.…”

“…It is important to mention that an increased risk of kidney injury may occur even in the absence of reductions in kidney function (i.e., reductions in GFR and/or elevations in serum creatinine) (Hess et al., 2022 ). Few studies have investigated the effects of heat acclimation on AKI incidence during subsequent heat stress.…”

Occupational Heat Stress Recommendation Compliance Attenuates AKI Risk Compared with a Work–Rest Ratio–Matched, Positive Control Scenario

“…Outdoor workers are regularly exposed to hot environments, 1 the frequency and intensity of which is predicted to increase because of climate change. 2 The resulting heat strain, that is, the physiologic effect of heat exposure, 3 increases the risk of AKI, as supported by findings from workplace, 3 laboratory-based human subjects, 4,5 and preclinical 6 studies. To mitigate the deleterious effects of heat, federal and non-federal entities issue exposure limit recommendations.…”

Sex differences in the association of long-term exposure to heat stress on kidney function in a large Taiwanese population study

“…However, existing literature on the differential impact of heat stress on kidney function between males and females is relatively sparse, particularly studies with a large sample size, and the outcomes of previous investigations have been heterogeneous, reflecting differences in study methodologies [18][19][20] . Consequently, our study aims to provide a comprehensive analysis of the association of heat stress on kidney function, explicitly accounting for sex-based differences.…”