Hot Weather; Adverse EffectAim1NCT04767347
Renal Considerations in the Heat Stress Recommendations
A study testing 23.0°C WBGT - Fixed Work Rate, 25.5°C WBGT - Fixed Work Rate and 27.5°C WBGT - Fixed Work Rate in people with Hot Weather; Adverse Effect and Kidney Dysfunction, run by Indiana University at 1 site in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 to 44 yearsHealthy volunteers can take part
- Conditions the study is for
- Hot Weather; Adverse Effect, Kidney Dysfunction, Kidney Injury
- What is being tested?
- 23.0°C WBGT - Fixed Work Rate, 25.5°C WBGT - Fixed Work Rate and 27.5°C WBGT - Fixed Work Rate
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 38 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Mar 2021to 4 May 2023
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 44 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Men and women
- 18-44 y old
- Body mass index ≤35.0 kg/m2
- Self-reported to be healthy.
Who cannot join
- 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)
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- 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
Trial locations and contacts
1 site in 1 country.
United States1 site
School of Public Health
Bloomington, Indiana, 47405-7109
About this study
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.
- Being tested
- 23.0°C WBGT - Fixed Work Rate, 25.5°C WBGT - Fixed Work Rate, 27.5°C WBGT - Fixed Work Rate, 28.5°C WBGT - Fixed Work Rate, 35.5°C WBGT - Fixed Work Rate
- Medical subject headings
- Hyperthermia, Dehydration
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
23.0°C WBGT - Fixed Work RateOther
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
25.5°C WBGT - Fixed Work RateOther
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
27.5°C WBGT - Fixed Work RateOther
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
28.5°C WBGT - Fixed Work RateOther
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
35.5°C WBGT - Fixed Work RateOther
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
26.0°C WBGT - Fixed work-to-rest ratioOther
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
30.5°C WBGT - Fixed work-to-rest ratioOther
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
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
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: 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. Receives: 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) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Peak urinary [IGFBP7•TIMP-2]
Kidney injury marker
Measured: through study completion, up to 20 weeks
Secondary outcomes (7)
Urinary NGAL
Kidney injury marker
Measured: through study completion, up to 20 weeks
Urinary IGFBP7
Kidney injury marker
Measured: through study completion, up to 20 weeks
Urinary TIMP-2
Kidney injury marker
Measured: through study completion, up to 20 weeks
Urinary IL-18
Kidney injury marker
Measured: through study completion, up to 20 weeks
Urinary L-FABP
Kidney injury marker
Measured: through study completion, up to 20 weeks
Renal artery blood velocity
Index of kidney blood flow
Measured: through study completion, up to 20 weeks
Segmental artery blood velocity
Index of kidney blood flow
Measured: through study completion, up to 20 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Feb 2021
- Study start1 Mar 2021
- Primary completion4 May 2023
- Study completion4 May 2023
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (3)Papers the sponsor has linked to this study.
- Other trials for Hot Weather; Adverse EffectStudies of the same condition, open and under way.
- More trials run by Indiana UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- This study will systematically examine the NIOSH recommendations for prescribing work-to-rest ratios during occupational heat stress on kidney function.
- Masking
- Double blind
- Who is masked
- Participant, Outcomes assessor
- Enrolment
- 38 participants (actual)
Sponsor and investigators
- Lead sponsor
- Indiana University
- Sponsor type
- University, hospital or other
- Collaborators
- State University of New York at Buffalo
- Responsible party
- Principal investigator, Zachary J. Schlader, Indiana University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04767347
- Sponsor's protocol ID
- 1902420140
- Acronym
- Aim1
- Status last verified
- Nov 2023
- First submitted
- 17 Feb 2021
- Last updated
- 8 Nov 2023
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Publications
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.
PubMed 40914830Hess 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.
PubMed 37907448Hess 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.
PubMed 36211944
Study at a glance
From the registry record, last updated by the sponsor on 8 Nov 2023. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Renal Considerations in the Heat Stress Recommendations
- ClinicalTrials.gov ID
- NCT04767347
- Acronym / sponsor ID
- Aim1 / 1902420140
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 38 participants (actual)
- Lead sponsor
- Indiana UniversityUniversity, hospital or other
- Collaborators
- State University of New York at Buffalo
- Study start
- 1 Mar 2021 (actual)
- Primary completion
- 4 May 2023 (actual)
- Study completion
- 4 May 2023 (actual)
- First posted
- 23 Feb 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, outcomes assessor)
- Number of arms
- 2
- Model description
- This study will systematically examine the NIOSH recommendations for prescribing work-to-rest ratios during occupational heat stress on kidney function.
| Arm | Type | Receives |
|---|---|---|
| Fixed Work Rate | Experimental | 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 RateParticipants 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 | Experimental | 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)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. |
Who may qualify
- Ages
- 18 to 44 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Men and women
- 18-44 y old
- Body mass index ≤35.0 kg/m2
- Self-reported to be healthy.
Key exclusion criteria (11 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| 23.0°C WBGT - Fixed Work RateFor 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 | Other | Fixed Work Rate |
| 25.5°C WBGT - Fixed Work RateFor 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 | Other | Fixed Work Rate |
| 27.5°C WBGT - Fixed Work RateFor 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 | Other | Fixed Work Rate |
| 28.5°C WBGT - Fixed Work RateFor 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 | Other | Fixed Work Rate |
| 35.5°C WBGT - Fixed Work RateFor 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 | Other | Fixed Work Rate |
| 26.0°C WBGT - Fixed work-to-rest ratioFor 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 | Other | Fixed work-to-rest ratio |
| 30.5°C WBGT - Fixed work-to-rest ratioFor 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 | Other | Fixed work-to-rest ratio |
| 30.5°C WBGT - Fixed work-to-rest ratio (high intensity)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 | Other | Fixed work-to-rest ratio |
Primary outcome
Peak urinary [IGFBP7•TIMP-2]
Time frame: through study completion, up to 20 weeks
Kidney injury marker
7 secondary outcomes
Urinary NGAL
Time frame: through study completion, up to 20 weeks
Urinary IGFBP7
Time frame: through study completion, up to 20 weeks
Urinary TIMP-2
Time frame: through study completion, up to 20 weeks
Urinary IL-18
Time frame: through study completion, up to 20 weeks
Urinary L-FABP
Time frame: through study completion, up to 20 weeks
Renal artery blood velocity
Time frame: through study completion, up to 20 weeks
Segmental artery blood velocity
Time frame: through study completion, up to 20 weeks
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 Nov 2023.
- Derived from this study: PubMed 40914830Hess 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.
- Derived from this study: PubMed 37907448Hess 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.
- Derived from this study: PubMed 36211944Hess 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.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing 23.0°C WBGT - Fixed Work Rate, 25.5°C WBGT - Fixed Work Rate and 27.5°C WBGT - Fixed Work Rate in people with Hot Weather; Adverse Effect and Kidney Dysfunction, run by Indiana University at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 11 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 8 Nov 2023. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Peak urinary [IGFBP7•TIMP-2] (time frame: through study completion, up to 20 weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT04767347, which also lists 3 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 8 Nov 2023; AzTrials last refreshed its copy on 6 Nov 2026.