Extreme Heat Stress in Older Adults: A Punch to the Gut, Kidneys or More?

Details

• Personal Author:
  Chapman CL ; Schlader ZJ
• Description:
  Older adults aged ≥65 years exposed to heat waves are particularly vulnerable to heat injury, which is characterized by hyperthermia (i.e., increased core temperature) and evidence of end-organ damage (e.g., kidneys, gastrointestinal tract, liver) in the absence of heat stroke. While heat illness exists on a continuum, ranging from heat exhaustion to heat stroke, heat injury is a form of heat illness of moderate-to-high severity that is less recognized despite strong epidemiological evidence of its adverse health effects. For example, the top causes of hospitalizations in older adults during heat waves are related to the kidneys (acute kidney injury (AKI) and fluid and electrolyte disturbances) (Chapman et al., 2021), indicating that heat injury is an important public health concern. The pathophysiology of heat injury is complex and integrated, likely stemming from hyperthermia-induced reductions in blood flow to the splanchnic vascular beds causing ischaemia, oxidative stress and gastrointestinal hyperpermeability (Meade et al., 2020). Surprisingly, however, there are few experimental studies in humans that have directly examined how older age modifies heat injury risk, specifically with end-organ damage outcomes, during heat stress. For example, McKenna, Atkins, Foster, et al. (2024) recently found that older adults had greater reductions in kidney function, indicative of AKI, compared to young adults (18-39 years) when exposed to a hot-dry environment (47 degrees C and 15% relative humidity) for 3 h. The older adults were more hyperthermic in this study. Thus, the primary role of older age for a given level of hyperthermia in end-organ responses could not be determined. In this issue of Experimental Physiology, McKenna, Atkins, Wallace, et al. (2025) addressed these limitations and provided further insight into the gastrointestinal and renal responses during heat stress when the magnitude of hyperthermia was matched between older and young adults. In nine older and nine young adults, the researchers used a water-perfused suit model of controlled hyperthermia (circulating 50 degrees C water) combined with cycling exercise at 20 W to mimic activities of daily living and control the magnitude of core and skin temperature increase until participants reached thermal tolerance. This methodological approach was a strength as it permitted assessments at the same level of hyperthermia in both age groups. The authors observed that small intestinal permeability increased in both groups and resulted in a mild inflammatory response. Moreover, older adults had higher gastroduodenal permeability compared to young adults. Reductions in kidney function (estimated glomerular filtration rate) did not differ between groups, while increases in pre-injury phase urinary AKI biomarkers (insulin-like growth factor-binding protein-7 (IGFBP7) × tissue inhibitor of metalloproteinases-2 (TIMP-2)) were not different between groups and there were no changes in injury phase urinary AKI biomarkers (neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1)). [Description provided by NIOSH]
• Subjects:
  Heat Stress Disorders Hot Temperature Occupational Health Safety
• Keywords:
  Author Keywords: AKI Body Temperature Gastrointenstinal Heat Stress Heat Wave Hot Environments Hyperthermia Kidney Function
• ISSN:
  0958-0670
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Birmingham Region [OSHA] ; Boston Region [OSHA] ; Chicago Region [OSHA] ; Indiana ; Massachusetts ; Tennessee
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  11-12
• Volume:
  110
• Issue:
  1
• NIOSHTIC Number:
  nn:20070639
• Citation:
  Exp Physiol 2025 Jan; 110(1):11-12
• Contact Point Address:
  Christopher L. Chapman, United States Army Research Institute of Environmental Medicine (USARIEM), Natick, MA 01760, USA
• Email:
  christopher.l.chapman22.ctr@health.mil
• Federal Fiscal Year:
  2025
• Performing Organization:
  Indiana University, Bloomington
• Peer Reviewed:
  False
• Start Date:
  20190901
• Source Full Name:
  Experimental Physiology
• End Date:
  20240831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:0229528bd888d335b7e0944a8afbb932e3056526f9bdb9e3d004c00dbfc84ba1b60769f42fa213f6b60c6361a62a3678fe44b16fccd76532cc95821881cf04d4
• Download URL:
  https://stacks.cdc.gov/view/cdc/208818/cdc_208818_DS1.pdf
• File Type:
  [PDF - 204.21 KB ]