Impact of indoor heat on mortality in the elderly

A team of researchers has developed a model to assess the impact of indoor heat on the health status of populations, and more specifically on the mortality of people over 65 years of age. 

In a study published last December in Environmental Health Perspectives, a team of researchers summarised the various studies correlating heat peaks and the risk of death. The researchers noted that the impact of exposure to indoor heat was a parameter that was not often studied. This is an important correlation, however, as the elderly, who are more vulnerable, spend 80-90% of their time at home. 


Previous studies show the relationship between heat peaks and the increase in the number of hospitalisations or emergency calls related to heat peaks (heart problems, dehydration, etc.). They indicate that children, the elderly or people with chronic illnesses are more vulnerable to heat. Heat-related deaths occur more frequently in people's homes, and mainly affect isolated or poor people (Fouillet et al. 2006; Kaiser et al. 2007; Semenza et al. 1996). 


In order to better assess the impact of indoor heat, the researchers developed a model based on data collected in a neighborhood in the city of Houston. Their goal is to propose a tool that could be used more systematically to better prevent health risks for the most vulnerable people. 


This model combines the following data, collected between 2000 and 2015:     

  • The number of deaths, obtained from death certificates provided by Texas Health Services. These certificates specify the cause of death,     
  • The number of emergency hospitalisations,     
  • Ozone concentration and meteorological data,     
  • An energy model of buildings (based on the EnergyPlus tool, already developed by the US Department of Energy). This model is used to estimate indoor temperatures hour by hour.  


Although the main raison d'être of this study is to provide a reusable tool to prevent heat-related health risks, a few figures could be extracted. Over the summer periods between 2000 and 2015, and with indoor temperatures ranging from 23 to 48.5°C, the following figures were found for people over 65 in Harris County, Texas: 


Number of deaths and emergecy admissions by cause

Cause of death or of the admission to the hospital 

Number of deaths 

Number of emergency hospital admissions 

Heat (including respiratory or circulatory problems) 

32,043 54,152

Circulatory problems 

24,513 34,484

Respiratory problems 

5,806 14,832



The authors conclude that the impact of heat on health is likely to be underestimated and that knowledge gaps remain regarding indoor heat and health thresholds, vulnerability, and adaptive capacity. 

Their study allows to quantify the extent to which short-term exposures to high indoor heat are associated with increased adverse health outcomes, especially death, among the elderly population.   

Additional data will be necessary to better understand variation in indoor thermal conditions, particularly in homes with central air conditioning.