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  • Is Physiological Equivalent Temperature (PET) a superior screening tool for heat stress risk than Wet-Bulb Globe Temperature (WBGT) index? Eight years of data from the Gothenburg half marathon

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Original research
Is Physiological Equivalent Temperature (PET) a superior screening tool for heat stress risk than Wet-Bulb Globe Temperature (WBGT) index? Eight years of data from the Gothenburg half marathon
  1. Sofia Thorsson1,
  2. David Rayner1,
  3. Gunnar Palm1,
  4. Fredrik Lindberg1,
  5. Eric Carlström2,3,
  6. Mats Börjesson4,5,
  7. Finn Nilson6,
  8. Amir Khorram-Manesh7,
  9. Björn Holmer1
  1. 1 Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden
  2. 2 Institute of Health Sciences, University of Gothenburg Sahlgrenska Academy, Goteborg, Sweden
  3. 3 Department of Business, Historical and Social Science, University of South-Eastern Norway - Campus Vestfold Library, Borre, Vestfold, Norway
  4. 4 Department of Molecular and Clinical Medicine, University of Gothenburg Institute of Medicine, Gothenburg, Sweden
  5. 5 Center for Health and Performance, University of Gothenburg Sahlgrenska Academy, Gothenburg, Sweden
  6. 6 Department of Life and Environmental Sciences, Karlstad University, Karlstad, Sweden
  7. 7 Department of Surgery, Institute of Clinical Sciences, University of Gothenburg Sahlgrenska Academy, Gothenburg, Sweden
  1. Correspondence to Professor Sofia Thorsson, Department of Earth Sciences, University of Gothenburg, Gothenburg SE-405 30, Sweden; sofia.thorsson{at}gvc.gu.se

Abstract

Background The Wet-Bulb Globe Temperature (WBGT) index is a common tool to screen for heat stress for sporting events. However, the index has a number of limitations. Rational indices, such as the physiological equivalent temperature (PET) and Universal Thermal Climate Index (UTCI), are potential alternatives.

Aim To identify the thermal index that best predicts ambulance-required assistances and collapses during a city half marathon.

Methods Eight years (2010–2017) of meteorological and ambulance transport data, including medical records, from Gothenburg’s half-marathon were used to analyse associations between WBGT, PET and UTCI and the rates of ambulance-required assistances and collapses. All associations were evaluated by Monte-Carlo simulations and leave-one-out-cross-validation.

Results The PET index showed the strongest correlation with both the rate of ambulance-required assistances (R2=0.72, p=0.008) and collapses (R2=0.71, p=0.008), followed by the UTCI (R2=0.64, p=0.017; R2=0.64, p=0.017) whereas the WBGT index showed substantially poorer correlations (R2=0.56, p=0.031; R2=0.56, p=0.033). PET stages of stress, match the rates of collapses better that the WBGT flag colour warning. Compared with the PET, the WBGT underestimates heat stress, especially at high radiant heat load. The rate of collapses increases with increasing heat stress; large increase from the day before the race seems to have an impact of the rate of collapses.

Conclusion We contend that the PET is a better predictor of collapses during a half marathon than the WBGT. We call for further investigation of PET as a screening tool alongside WBGT.

  • running
  • exertional heat stress
  • marathon

Data availability statement

Data may be obtained from a third party and are not publicly available. The data are based on ambulance patient records and registers from the Gothenburg half marathon organisation. According to the ethical permission, deidentified data can be shared to other researchers involved in a linked study e.g. for comparative reasons. The data can be obtained from the first author, ST or EC (coauthor). There is no time limit on the availability of the data.

https://doi.org/10.1136/bjsports-2019-100632

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    Data availability statement

    Data may be obtained from a third party and are not publicly available. The data are based on ambulance patient records and registers from the Gothenburg half marathon organisation. According to the ethical permission, deidentified data can be shared to other researchers involved in a linked study e.g. for comparative reasons. The data can be obtained from the first author, ST or EC (coauthor). There is no time limit on the availability of the data.

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    Footnotes

    • Contributors ST led the study. All authors, ST, GP, FL, DR, EC, MB, FN, AK-M and BH conceived the study and provided input on the study design. EC and AK-M selected medical records for the study period. GP, FL and DR collected and processed the metrological data. FL, GP and ST calculated the thermal indices. DR, ST and BH analysed the data. ST drafted the manuscript. All authors edited and approved the final version of the paper.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

    • Provenance and peer review Not commissioned; externally peer reviewed.