HeatSuite Phoenix Pilot: Assesing Non-life Threatening Health Outcomes to Extreme Heat in Older Adults Living in Phoenix, Arizona

Extreme heat is experienced at higher intensity and duration in cities worldwide. Understanding how heat impacts people's lives is vital to creating solutions that support well-being. However, methodological research gaps that relate personal heat exposures (PHE) to impacts on behavior and illness have led to a lack of empirical data on individuals in free-living conditions. Setting the ground for a virtual, international, and community-driven NSF Global Center for Heat Adaptation, this research makes part of a new research pilot to better understand the pathways from exposure to individual-level responses that result in adverse heat-health outcomes.

We collected ecologically valid data on indoor/outdoor exposures alongside behavior, health impacts, and perception during the summer of 2024 in Phoenix, Arizona, USA, using the HeatSuite™ system. This measuring system gathers air temperature and humidity exposure at home and, paired with an open-source smartwatch, integrates blood pressure measures, near skin and oral temperature, heart rate, location, and self-reports of thermal perception, sleep, urination, thirst, and heat-related symptoms (fatigue, headache, concentration problems, dizziness, stress). With pre-and post-surveys to inform the HeatSuite™ measurements with the participant's backgrounds, the whole dataset allows us to comprehensively assess how resources (including housing type), knowledge, health status, etc., affect behavior and health responses.

Intra- and inter-subject experiences with the heat of 43 individuals (>45 years) from diverse socio-economic backgrounds were analyzed using measurements of time-varying PHE, associated health responses, and behavior measured during 21-day periods from May to October. Participants of this research dwelled in single-unit, multi-unit, and manufactured homes. Finally, we estimate the range of theoretically safe (liveable) activities and contrast that information with the occurrence of health outcomes and activity level proxies.

Results show marked differences in indoor vs. outdoor exposure and why adequate housing is crucial for surviving Phoenix's summer heat. We also fVariability in health outcomes partially corresponds to heat exposures and heat avoided (as a proxy of the adaptative response) but also is related to adaptative capacities of individuals (thermal preferences, pre-existent medical conditions, heat mitigation strategies, risk perception towards heat, socioeconomics, social capital, demographics, and the time spent indoors vs outdoors). This work demonstrates the importance of capturing individual-level variability in physiological, behavioral, and/or socio-ecological factors predisposing people to adverse heat-related outcomes in real-world exposures. It provides a practical framework for understanding individual heat adaptation, enabling the creation of context-based mitigation strategies.