An empirical mechanistic framework for heat-related illness

A physiologically based, mechanistic framework was developed to understand key risk factors associated with adverse health effects from heat waves. Th e framework consists of a number of integrated transdisciplinary modules. E nvironmental conditions and behavioral responses link to a physiological mo del, which predicts core temperature. Core temperature over time is then co nverted into a time-at-temperature metric. The output of the framework is a heat-related health effects index (HEI), reflecting the potential relative severity of the heat stress on health. The framework is flexible, allowing the individual models to be adapted to conditions at specific locations an d to be updated as new information becomes available. Scenario analyses are easily accommodated, enabling the framework to evaluate issues such as int ervention strategies and the possible effects of global climate change on h eat-related illnesses. The framework and an initial set of component models were applied to conditions during the 1995 Chicago event and the results c ompared with published studies. For individuals, there was reasonably good agreement between HEI ratios and actual mortality risk ratios when comparin g indoor versus outdoor environments. When aggregating across populations, predicted HEI ratios were significantly smaller than actual mortality ratio s when comparing healthy versus compromised populations, supporting the not ion that mortality may not be the best indicator of heat stress effects. Fu ture work should include refinement of the initial models and application t o other cities and heat events.