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Completed

NCT Number: NCT05303142

Comparing Exertional Heat Illness Risk Factors Between Patients and Controls

The arduous nature of military training and operations require personnel to encounter high heat load, e.g., during intense physical exertion, particularly in the heat. These conditions reduce operational effectiveness and expose personnel to a risk of incapacitation and death from exertional heat illness (EHI). The primary aim of this study is to compare putative 'chronic' EHI risk factors between a cohort who have suffered a history of EHI and a control cohort with no EHI history. The secondary aim is to examine the influence of these EHI risk factors on thermoregulation during a standard heat tolerance assessment.

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Key information

Conditions

Exertional Heat Illness Heat Stress Disorders Wounds and Injuries

Age range

18 year–40 year

Sex eligibility

All sexes

Study type

Observational

Primary location

University of Portsmouth

Portsmouth, Hampshire, PO1 2UP, United Kingdom

About this study

Military training and operations present a risk of incapacitation and death from Exertional Heat Illness (EHI). However, widely accepted EHI risk factors are absent in almost half of all United Kingdom (UK) military EHI cases, indicating that a significant number of EHI cases in military personnel involve alternative risk factors. Risk factors for EHI can been classified along a spectrum ranging from acute (e.g. recent poor sleep) to chronic (e.g. low fitness), with the role of chronic risk factors supported by the observation that individuals who have suffered an EHI are at a substantially increased risk of subsequent EHI. The primary aim of this study is to compare putative 'chronic' EHI risk factors (e.g. composition of gastrointestinal (GI) microbiome, infection and inflammation, trait-like psychological factors) between a cohort who have suffered a history of EHI and a control cohort with no EHI history. The secondary aim is to examine the influence of these EHI risk factors on thermoregulation during a standard heat tolerance assessment.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Individuals with a history of EHI:

  • Previous EHI episode
  • Normal resting ECG
  • Male or female
  • 18 - 40 years

Control participants:

  • No previous history of EHI
  • Normal resting ECG
  • Male or female
  • 18 - 40 years

Treatment and study plan

Heat Tolerance Assessment

Other

60-90 minutes exercise in hot (34 °C; 45% R.H.) conditions at 60%VO2max

Primary outcomes

  1. Core temperature

    Time frame: At 60 minutes (or test termination if earlier) of Heat Tolerance Assessment

    Measured using a rectal thermistor.

  2. Core temperature

    Time frame: Rate of rise from 30 to 60 minutes (or test termination if earlier) of Heat Tolerance Assessment

    Measured using a rectal thermistor.

  3. Diversity of gastrointestinal microbiota

    Time frame: Baseline

    Measured in stool sample. Assessed by alpha diversity score.

  4. Diversity of gastrointestinal microbiota

    Time frame: Baseline

    Measured in stool sample. Assessed by beta diversity score.

  5. Abundance of gastrointestinal microbiota

    Time frame: Baseline

    Measured in stool sample. Assessed at level of phylum.

  6. Detection of sexually transmitted pathogens

    Time frame: Baseline

    Assessed from urine sample. Measured using cobas CT/NG assays.

  7. Detection of respiratory pathogens

    Time frame: Baseline

    Assessed from throat swab. Measured using Allplex assays.

  8. Detection of gastrointestinal pathogens

    Time frame: Baseline

    Assessed from stool swab. Measured using Allplex.

  9. Circulating Interleukin 6

    Time frame: Baseline

    Measured using ELISA

  10. Circulating Interleukin 6

    Time frame: Post Heat Tolerance Assessment (within 15 minutes of test end)

    Measured using ELISA

  11. Circulating C-Reactive Protein

    Time frame: Baseline

    Measured using ELISA

  12. Circulating C-Reactive Protein

    Time frame: Post Heat Tolerance Assessment (within 15 minutes of test end)

    Measured using ELISA

  13. Circulating Claudin 3

    Time frame: Baseline

    Measured using ELISA

  14. Circulating Claudin 3

    Time frame: Post Heat Tolerance Assessment (within 15 minutes of test end)

    Measured using ELISA

  15. Circulating Zonulin

    Time frame: Baseline

    Measured using ELISA

  16. Circulating lipopolysaccharide binding protein

    Time frame: Baseline

    Measured using ELISA

  17. Circulating lipopolysaccharide binding protein

    Time frame: Post Heat Tolerance Assessment (within 15 minutes of test end)

    Measured using ELISA

  18. Circulating intestinal fatty acid binding protein

    Time frame: Baseline

    Measured using ELISA

  19. Circulating intestinal fatty acid binding protein

    Time frame: Post Heat Tolerance Assessment (within 15 minutes of test end)

    Measured using ELISA

  20. Gastrointestinal illness symptomology questionnaire

    Time frame: Baseline

    Visual analogue scale (0-10). Higher scores indicate worse symptomology

  21. Gastrointestinal illness symptomology questionnaire

    Time frame: Pre Heat Tolerance Assessment

    Visual analogue scale (0-10). Higher scores indicate worse symptomology

  22. Gastrointestinal illness symptomology questionnaire

    Time frame: Immediately post Heat Tolerance Assessment

    Visual analogue scale (0-10). Higher scores indicate worse symptomology

  23. Respiratory illness symptomology, measured by Jackson common cold questionnaire

    Time frame: Baseline

    Higher scores indicate worse symptomology

  24. Sleep quality and quantity, measured by Pittsburgh Sleep Quality Index

    Time frame: Baseline -3 days

    Higher scores indicate worse sleep

  25. Motivation, measured by Motivation scale

    Time frame: Baseline -3 days

  26. State-trait anxiety, measured by state-trait anxiety inventory form Y-2

    Time frame: Baseline -3 days

  27. Risk taking, measured by the risk-taking inventory

    Time frame: Baseline -3 days

  28. Resilience, measured by the Connor-Davidson resilience scale

    Time frame: Baseline -3 days

  29. Stress, measured by perceived stress scale

    Time frame: Baseline -3 days

  30. Mental readiness

    Time frame: Baseline

    Visual analogue scale (0-100). Higher scores indicate a lower state of mental readiness.

  31. Stress

    Time frame: Baseline

    Visual analogue scale (0-100). Higher scores indicate a greater state of stress.

Secondary outcomes

  1. Heat rate

    Time frame: At 5 minute intervals during the Heat Tolerance Assessment

  2. Thermal comfort

    Time frame: At 15 minute intervals during Heat Tolerance Assessment

    Modified 9 point Gagge scale. Higher scores indicate worse comfort.

  3. Thermal sensation

    Time frame: At 15 minute intervals during Heat Tolerance Assessment

    Modified 9 point Gagge scale. Higher scores indicate hotter sensation

  4. Rating of Perceived Exertion

    Time frame: At 15 minute intervals during Heat Tolerance Assessment

    6-20 Borg scale. Higher scores indicate higher perceived exertion

  5. Skin Temperature

    Time frame: During Heat Tolerance Assessment

    Weighted mean skin temperature

  6. Sweat rate

    Time frame: During Heat Tolerance Assessment

    Determined from change in nude body mass during the heat tolerance assessment

Other outcomes

  1. Body mass

    Time frame: Baseline

  2. Relative maximal aerobic fitness

    Time frame: Baseline

    Highest value measured in ml.kg-1.min-1 during a treadmill graded exercise test.

  3. Urine osmolality

    Time frame: Baseline

    Measured using freezing point depression

Sponsors and collaborators

Lead sponsor

University of Portsmouth

Other

Collaborators

  • Headquarters Army Recruiting and Initial Training Command (UK)
  • Institute of Naval Medicine (UK)
  • Liverpool John Moores University
  • Public Health Wales

Registry information

Official study title

Comparison of Novel Putative Risk Factors for Exertional Heat Illness Between a Military Patient Cohort and Matched Control Cohort During Exercise Heat Stress

Important dates

Study start
2022
Primary completion
2023
Study completion
2023
First posted
Mar 31, 2022
Registry last updated
May 22, 2023

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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