TOPLINE:
Older adults show an increase in creatinine and cystatin C levels after exposure to extreme heat in a dry setting despite staying hydrated; however, changes in these kidney function biomarkers are much more modest in a humid setting and in young adults.
METHODOLOGY:
- Older adults are vulnerable to heat-related morbidity and mortality, with kidney complications accounting for many excess hospital admissions during heat waves.
- Researchers investigated plasma-based markers of kidney function following extreme heat exposure for 3 hours in 20 young (21-39 years) and 18 older (65-76 years) adults recruited from the Dallas-Fort Worth area.
- All participants underwent heat exposure in a chamber at 47 °C (116 °F) and 15% relative humidity (dry setting) and 41 °C (105 °F) and 40% relative humidity (humid setting) on separate days. They performed light physical activity mimicking their daily tasks and drank 3 mL/kg body mass of water every hour while exposed to heat.
- Blood samples were collected at baseline, immediately before the end of heat exposure (end-heating), and 2 hours after heat exposure.
- Plasma creatinine was the primary outcome, with a change ≥ 0.3 mg/dL considered as clinically meaningful. Cystatin C was the secondary outcome.
TAKEAWAY:
- The plasma creatinine level showed a modest increase from baseline to end-heating (difference, 0.10 mg/dL; P = .004) and at 2 hours post exposure (difference, 0.17 mg/dL; P < .001) in older adults facing heat exposure in the dry setting.
- The mean cystatin C levels also increased from baseline to end-heating by 0.29 mg/L (P = .01) and at 2 hours post heat exposure by 0.28 mg/L (P = .004) in older adults in the dry setting.
- The mean creatinine levels increased by only 0.06 mg/dL (P = .01) from baseline to 2 hours post exposure in older adults facing heat exposure in the humid setting.
- Young adults didn’t show any significant change in the plasma cystatin C levels during or after heat exposure; however, there was a modest increase in the plasma creatinine levels after 2 hours of heat exposure (difference, 0.06; P = .004).
IN PRACTICE:
“These findings provide limited evidence that the heightened thermal strain in older adults during extreme heat may contribute to reduced kidney function,” the authors wrote.
SOURCE:
The study was led by Zachary J. McKenna, PhD, from the Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, and was published online in JAMA.
LIMITATIONS:
The use of plasma-based markers of kidney function, a short laboratory-based exposure, and a small number of generally healthy participants were the main limitations that could affect the generalizability of this study’s findings to broader populations and real-world settings.
DISCLOSURES:
The National Institutes of Health and American Heart Association funded this study. Two authors declared receiving grants and nonfinancial support from several sources.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication. A version of this article appeared on Medscape.com.