Renal Considerations in the Heat Stress Recommendations

NCT04767347 | Completed

• 1 other identifier: 1902420140
• Study Type: interventional
• Target: 38
• Locations: 1 country
• Sites: 1

Brief Summary

An epidemic of chronic kidney disease is occurring in laborers who undertake physical work outdoors in hot conditions. The reason for this is unknown, but may be related to kidney dysfunction caused by increases in body temperature and dehydration. The current heat stress recommendations for workers were not developed with regards for kidney health. The purpose of this study is to determine if the current recommendations protect against kidney dysfunction.

Conditions

Hot Weather; Adverse Effect; Kidney Dysfunction; Kidney Injury; Hyperthermia; Dehydration

Outcome Measures

Primary Outcomes (1)

• Peak urinary [IGFBP7•TIMP-2]

  Kidney injury marker

  through study completion, up to 20 weeks

Secondary Outcomes (7)

• Urinary NGAL

  through study completion, up to 20 weeks

• Urinary IGFBP7

  through study completion, up to 20 weeks

• Urinary TIMP-2

  through study completion, up to 20 weeks

• Urinary IL-18

  through study completion, up to 20 weeks

• Urinary L-FABP

  through study completion, up to 20 weeks

Other Outcomes (17)

• Core body temperature

  through study completion, up to 20 weeks

• Mean skin temperature

  through study completion, up to 20 weeks

• Oxygen uptake

  through study completion, up to 20 weeks

Study Arms (2)

Fixed Work Rate

EXPERIMENTAL

Participants will walk on a treadmill at 3 mph and the grade will be adjusted to elicit 430 W of metabolic heat production (the most common work intensity). This study will systematically examine the NIOSH recommendations for prescribing work-to-rest ratios with increasing environmental heat stress (defined as Wet Bulb Globe Temperature, WBGT) at this fixed rate of metabolic heat production on kidney function.

Other: 23.0°C WBGT - Fixed Work Rate; Other: 25.5°C WBGT - Fixed Work Rate; Other: 27.5°C WBGT - Fixed Work Rate; Other: 28.5°C WBGT - Fixed Work Rate; Other: 35.5°C WBGT - Fixed Work Rate

Fixed work-to-rest ratio

EXPERIMENTAL

This study will systematically examine the NIOSH recommendations on changes in kidney function when the work-to-rest ratio is fixed at 30 min per hour (the most commonly prescribed work-to-rest ratio), but the rate of metabolic heat production and environmental heat stress differs (Figure 2). As described in Study 1, the appropriate rate of metabolic heat production will be elicited by having participants walk on a treadmill at 3 mph and the grade will be adjusted accordingly.

Other: 26.0°C WBGT - Fixed work-to-rest ratio; Other: 30.5°C WBGT - Fixed work-to-rest ratio; Other: 30.5°C WBGT - Fixed work-to-rest ratio (high intensity)

Interventions

23.0°C WBGT - Fixed Work Rate OTHER

For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 23.0°C WBGT (29°C, 46% relative humidity) @ 60 min exercise per hour

Fixed Work Rate

25.5°C WBGT - Fixed Work Rate OTHER

For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 25.5°C WBGT (31°C, 52% relative humidity) @ 45 min exercise per hour

Fixed Work Rate

27.5°C WBGT - Fixed Work Rate OTHER

For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 27.5°C WBGT (33°C, 53% relative humidity) @ 30 min exercise per hour

Fixed Work Rate

28.5°C WBGT - Fixed Work Rate OTHER

For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 28.5°C WBGT (34°C, 54% relative humidity) @ 15 min exercise per hour

Fixed Work Rate

35.5°C WBGT - Fixed Work Rate OTHER

For four hours, participants will walk on a treadmill to elicit 430 W of metabolic heat production in the following conditions: 35.5°C WBGT (40°C, 65% relative humidity) @ 15 min exercise per hour

Fixed Work Rate

26.0°C WBGT - Fixed work-to-rest ratio OTHER

For four hours, participants will walk on a treadmill at differing levels of metabolic heat production and environmental conditions (noted below), but at a fixed work-rest ratio of 30 minutes per hour. 26.0°C WBGT (31°C, 55% relative humidity) @ 530 W metabolic heat production

Fixed work-to-rest ratio

30.5°C WBGT - Fixed work-to-rest ratio OTHER

For four hours, participants will walk on a treadmill at differing levels of metabolic heat production and environmental conditions (noted below), but at a fixed work-rest ratio of 30 minutes per hour. 30.5°C WBGT (36°C, 55% relative humidity) @ 230 W metabolic heat production

Fixed work-to-rest ratio

30.5°C WBGT - Fixed work-to-rest ratio (high intensity) OTHER

For four hours, participants will walk on a treadmill at differing levels of metabolic heat production and environmental conditions (noted below), but at a fixed work-rest ratio of 30 minutes per hour. 30.5°C WBGT (36°C, 55% relative humidity) @ 530 W metabolic heat production

Fixed work-to-rest ratio

Eligibility Criteria

• Age: 18 Years - 44 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Men and women
• y old
• Body mass index ≤35.0 kg/m2
• Self-reported to be healthy.

You may not qualify if:

• Not within defined age range
• Estimated glomerular filtration rate (eGFR) \< 60 mL/min/1.73m2
• Deemed highly active according to the physical activity questionnaire (i.e., \>3500 MET\*min/wk)
• Body mass index \>35.0 kg/m2
• Current or history of any renal disease, heart disease, stroke, immune or autoimmune disease, and/or gastrointestinal disease/surgery
• Hypertension during screening (systolic blood pressure \>139 or diastolic blood pressure \>89)
• Using medications that blunt the physiological response to exercise (e.g., beta blockers)
• Prescription medication with a known side effect of impaired temperature regulation or fluid balance (e.g., diuretics)
• Positive pregnancy test at any time during the study or breast feeding
• Current tobacco or electronic cigarette use or consistent use within the last 2 years
• Inability to safely complete the peak oxygen uptake test

Sponsors & Collaborators

• Indiana University: lead
• State University of New York at Buffalo: collaborator

Study Sites (1)

School of Public Health

Bloomington, Indiana, 47405-7109, United States

Location

Related Publications (3)

• Hess HW, Hite MJ, Heikkinen ME, Tarr ML, Tourula E, Johnson BD, Hostler D, Schlader ZJ. Critical Assessment of the Recommended Alert Limit Curves for Occupational Heat Exposure. Am J Ind Med. 2025 Nov;68(11):1004-1012. doi: 10.1002/ajim.70022. Epub 2025 Sep 7.

  PMID: 40914830 DERIVED

• Hess HW, Baker TB, Tarr ML, Zoh RS, Johnson BD, Hostler D, Schlader ZJ. Occupational Heat Stress Recommendation Compliance Attenuates AKI Risk Compared with a Work-Rest Ratio-Matched, Positive Control Scenario. Kidney360. 2023 Dec 1;4(12):1752-1756. doi: 10.34067/KID.0000000000000288. Epub 2023 Nov 1.

  PMID: 37907448 DERIVED

• Hess HW, Tarr ML, Baker TB, Hostler D, Schlader ZJ. Ad libitum drinking prevents dehydration during physical work in the heat when adhering to occupational heat stress recommendations. Temperature (Austin). 2022 Jul 20;9(3):292-302. doi: 10.1080/23328940.2022.2094160. eCollection 2022.

  PMID: 36211944 DERIVED

MeSH Terms

Conditions

Hyperthermia; Dehydration

Condition Hierarchy (Ancestors)

Body Temperature Changes; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Heat Stress Disorders; Wounds and Injuries; Water-Electrolyte Imbalance; Metabolic Diseases; Nutritional and Metabolic Diseases; Pathologic Processes

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: The participant will not be directly informed of the experimental conditions and will be blinded to the hypotheses. The outcomes assessor will be blinded to the experimental conditions when analyzing the data.
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Associate Professor of Kinesiology

Model Details: This study will systematically examine the NIOSH recommendations for prescribing work-to-rest ratios during occupational heat stress on kidney function.

Study Record Dates

• First Submitted: February 17, 2021
• First Posted: February 23, 2021
• Study Start: March 1, 2021
• Primary Completion: May 4, 2023
• Study Completion: May 4, 2023
• Last Updated: November 8, 2023

Record last verified: 2023-11

Locations

US (1)