Development of heat stress charts for older people under indoor environmental conditions

Abstract

It has been acknowledged that as outdoor temperature and relative humidity increase past threshold values, so do older people mortality and morbidity rates. Similarly, there exist indoor conditions of temperature (Tamb) and relative humidity (RH) that would pose a health-risk to older people when they are exposed to these conditions for extended periods. However, these indoor conditions need to be identified to set protective measures for this vulnerable population. The aim of this work is to develop heat stress indices for older people similar to the standard effective temperature (SET) for a wide range of indoor conditions, activity levels and clothing insulation. A robust and validated bioheat model for older people was used to predict thermal responses and deduce the limits of Tamb and RH that would present a heat-related health risk when the core temperature exceeds 38 °C, or percentage of body water loss exceeds 2%, or when skin wettedness and SET exceed given thresholds. The results were consistent with published experimental data. At relatively cool ambient conditions, Tamb < 21 °C, older people have higher mean skin temperatures and feel cooler than younger people. At Tamb ≥ 25 °C, older people have lower mean skin temperatures and SET values become greater than younger ones, indicating that older people would rate their indoor conditions more stressful than younger people.