title: Susceptibility to exertional heat illness and hospitalisation risk in UK military personnel.
abstract: BACKGROUND
  Susceptibility to exertional heat illness (EHI) is considered multifactorial in nature. The aims of this study were to (1) review traditional susceptibility factors identified in cases of EHI and (2) determine how they are related to risk of hospitalisation.
  
  
  METHODS
  Review of an electronic database of EHI reported in the British Army between 1 September 2007 and 31 December 2014. Cases were categorised by demographic, situational and susceptibility variables. Univariate and multivariate logistic regression was performed for the OR for hospitalisation by risk factor.
  
  
  RESULTS
  361 reports were included in the analysis. 33.5% of cases occurred in hot climates, 34.6% in temperate climates during summer months and 31.9% in temperate climates outside of summer months. Traditional susceptibility factors were reported in 193 but entirely absent from 168 cases. 137 cases (38.0%) were admitted to hospital. Adjusted OR for hospitalisation was lower for recruits (OR 0.42, 95% CI 0.18 to 0.99, p<0.05) and for personnel wearing occlusive dress (OR 0.56, 95% CI 0.34 to 0.93, p<0.05) or unacclimatised to heat (OR 0.31, 95% CI 0.15 to 0.66, p<0.01).
  
  
  CONCLUSIONS
  The global, year-round threat of EHI is highlighted. Absence of susceptibility factors in nearly half of reports highlights the challenge of identifying EHI-prone individuals. Paradoxical association of traditional susceptibility factors with reduced hospitalisation risk may reflect the contemporary contexts in which severe EHI occurs. These findings also suggest a need for better evidence to inform guidelines that aim to prevent severe EHI concurrent to reducing overall morbidity.
authors.affiliation: Section of Anaesthetics, Pain Medicine and Intensive Care, Imperial College, London, UK; Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Stacey
authors.affiliation: Department of Military Medicine , Royal Centre for Defence Medicine , Birmingham , UK.
authors.forename: Iain T
authors.initials: IT
authors.lastname: Parsons
authors.affiliation: Department of Military Medicine, Royal Centre for Defence Medicine, Birmingham, UK; Professor of Sport and Exercise Endocrinology, Carnegie Faculty, Leeds Beckett University, Leeds UK.
authors.forename: David R
authors.initials: DR
authors.lastname: Woods
authors.affiliation: Thyroid Research Group, Institute of Molecular & Experimental Medicine, Cardiff University School of Medicine, Cardiff, UK.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Taylor
authors.affiliation: Parkes Professor of Preventive Medicine, Army Health Unit, Former Army Staff College, Camberley, UK.
authors.forename: David
authors.initials: D
authors.lastname: Ross
authors.affiliation: Section of Anaesthetics, Pain Medicine and Intensive Care, Imperial College, London, UK; Reader in Critical Care, Centre for Perioperative Medicine and Critical Care Research, Imperial College Healthcare NHS Trust, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: J Brett
keywords: Environment; Heat acclimatisation; Heat stress