A thermo-physiologically consistent approach for studying the heat-health nexus with hierarchical generalized additive modelling: Application in Athens urban area (Greece)

Abstract

The significance of the thermo-physiological determinants of heat-related deaths has been recognized since antiquity. Still, the impact of heat on human health in the modern era is repeatedly assessed in the epidemiological literature based solely on the environmental drivers of heat stress, primarily using aggregated daily metrics of air temperature. Going beyond this simplified approach, here we showcase a prototype heat-health modelling method that incorporates thermo-physiological principles and accounts for variability across different regions and populations, using the advanced human-biometeorological mPET (modified Physiologically Equivalent Temperature) index. This novel approach is based on a hierarchical general additive modelling framework. By applying the framework in the vulnerable to heat stress Athens urban area in Greece, we demonstrate, for the first time in epidemiological terms, that fatal heat-related risk is strongly associated with daylong (> 6 h) strong heat stress exposure. We also show that atmospherically and thermo-physiologically driven location- and population-specific variations in exposure, as well as short-term acclimatization, contribute to heat-effect occurrence and modification. These novel outcomes assist in establishing links between environmental epidemiological and thermo-physiological research. This is of great importance for supporting robust and effective public health interventions, especially in cities, which are particularly heat stress susceptible.