title: Defining indoor heat thresholds for health in the UK.
abstract: BACKGROUND
  It has been recognised that as outdoor ambient temperatures increase past a particular threshold, so do mortality/morbidity rates. However, similar thresholds for indoor temperatures have not yet been identified. Due to a warming climate, the non-sustainability of air conditioning as a solution, and the desire for more energy-efficient airtight homes, thresholds for indoor temperature should be defined as a public health issue.
  
  
  OBJECTIVE
  The aim of this paper is to outline the need for indoor heat thresholds and to establish if they can be identified. Our objectives include: describing how indoor temperature is measured; highlighting threshold measurements and indices; describing adaptation to heat; summary of the risk of susceptible groups to heat; reviewing the current evidence on the link between sleep, heat and health; exploring current heat and health warning systems and thresholds; exploring the built environment and the risk of overheating; and identifying the gaps in current knowledge and research.
  
  
  METHODS
  A global literature search of key databases was conducted using a pre-defined set of keywords to retrieve peer-reviewed and grey literature. The paper will apply the findings to the context of the UK.
  
  
  RESULTS
  A summary of 96 articles, reports, government documents and textbooks were analysed and a gap analysis was conducted. Evidence on the effects of indoor heat on health implies that buildings are modifiers of the effect of climate on health outcomes. Personal exposure and place-based heat studies showed the most significant correlations between indoor heat and health outcomes. However, the data are sparse and inconclusive in terms of identifying evidence-based definitions for thresholds. Further research needs to be conducted in order to provide an evidence base for threshold determination.
  
  
  CONCLUSIONS
  Indoor and outdoor heat are related but are different in terms of language and measurement. Future collaboration between the health and building sectors is needed to develop a common language and an index for indoor heat and health thresholds in a changing climate.
authors: Extreme Events and Health Protection Section, London, UK. exeter95@hotmail.com
authors: Mindy
authors: M
authors: Anderson
authors: Catriona
authors: C
authors: Carmichael
authors: Virginia
authors: V
authors: Murray
authors: Andy
authors: A
authors: Dengel
authors: Michael
authors: M
authors: Swainson
mesh_terms: D000367:Age Factors; D000389:Air Conditioning / Q000009:adverse effects / Q000592:standards* / Q000639:trends; D002028:Building Codes / Q000592:standards; D057231:Climate Change; D006304:Health Status; D006361:Heating / Q000009:adverse effects / Q000592:standards*; D006358:Hot Temperature / Q000009:adverse effects*; D006798:Housing / Q000592:standards*; D006801:Humans; D059205:Renewable Energy / Q000592:standards; D012890:Sleep / Q000502:physiology; D006113:United Kingdom