Renal Considerations in the Heat Stress Recommendations

Not Applicable

Completed

• Conditions: Hot Weather; Adverse Effect; Dehydration; Kidney Injury; Kidney Dysfunction; Hyperthermia
• Interventions: Other: 26.0°C WBGT - Fixed work-to-rest ratio; Other: 23.0°C WBGT - Fixed Work Rate; Other: 25.5°C WBGT - Fixed Work Rate; Other: 30.5°C WBGT - Fixed work-to-rest ratio; Other: 27.5°C WBGT - Fixed Work Rate; Other: 30.5°C WBGT - Fixed work-to-rest ratio (high intensity); Other: 28.5°C WBGT - Fixed Work Rate; Other: 35.5°C WBGT - Fixed Work Rate

• Registration Number: NCT04767347
• Lead Sponsor: Indiana University

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.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2021-02-17
• Study First Submitted QC: 2021-02-19
• Study First Posted: 2021-02-23
• Study Start: 2021-03-01
• Primary Completion: 2023-05-04
• Study Completion: 2023-05-04
• Status Verified: 2023-11
• Last Update Submitted: 2023-11-06
• Last Update Posted: 2023-11-08

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 38

Inclusion Criteria

• Men and women
• 18-44 y old
• Body mass index ≤35.0 kg/m2
• Self-reported to be healthy.

Exclusion Criteria

• 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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Fixed Work Rate	25.5°C WBGT - Fixed Work Rate	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.
Fixed Work Rate	27.5°C WBGT - Fixed Work Rate	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.
Fixed Work Rate	35.5°C WBGT - Fixed Work Rate	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.
Fixed work-to-rest ratio	26.0°C WBGT - Fixed work-to-rest ratio	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.
Fixed Work Rate	23.0°C WBGT - Fixed Work Rate	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.
Fixed Work Rate	28.5°C WBGT - Fixed Work Rate	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.
Fixed work-to-rest ratio	30.5°C WBGT - Fixed work-to-rest ratio	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.
Fixed work-to-rest ratio	30.5°C WBGT - Fixed work-to-rest ratio (high intensity)	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.

Primary Outcome Measures

Name	Time	Method
Peak urinary [IGFBP7•TIMP-2]	through study completion, up to 20 weeks	Kidney injury marker

Secondary Outcome Measures

Name	Time	Method
Urinary IL-18	through study completion, up to 20 weeks	Kidney injury marker
Urinary TIMP-2	through study completion, up to 20 weeks	Kidney injury marker
Renal artery blood velocity	through study completion, up to 20 weeks	Index of kidney blood flow
Urinary NGAL	through study completion, up to 20 weeks	Kidney injury marker
Urinary L-FABP	through study completion, up to 20 weeks	Kidney injury marker
Urinary IGFBP7	through study completion, up to 20 weeks	Kidney injury marker
Segmental artery blood velocity	through study completion, up to 20 weeks	Index of kidney blood flow

Trial Locations

Locations (1)

School of Public Health; 🇺🇸 Bloomington, Indiana, United States