While the number of heat wave days in France will likely continue to increase over the
century, extreme heat is associated with excess mortality and morbidity in urban heat
islands. The first objective of H3Sensing is to investigate outdoor environmental,
building, dwelling, situational, and behavioral determinants of objectively assessed
personal heat stress over daily movements during warm periods. We will explore
environmental determinants associated with micro-urban heat islands at an unprecedented
level of accuracy; we will assess building and dwelling characteristics associated with
in-home heat stress; and we will examine how daily activities (trips, etc.) and practices
(how people dress, manage heat at home) contribute to heat stress. The second aim is to
investigate how these heat stress determinants and momentary and cumulated heat stress
itself are related to physiological indicators of heat stress, sleep, thermal discomfort,
and well-being. One hundred eighty (180) participants recruited through internet
advertisements will be followed over 4 day periods in March-May and then a second time in
June-September 2025. Research assistants will use a detailed assessment sheet (defined
from the a priori visit to 10 dwellings) to collect information on building and dwelling
characteristics. Participants will carry a smartphone with a GPS receiver and the Eco Emo
tracker application permitting to identify their trips and visited places and to collect
additional information on these trips (including their access to air conditioned). GPS
data will permit to dynamically assess exposures in participants' everyday mobility. To
move beyond simplistic assessments of personal heat stress, we will assess it in an
ambulatory way considering personal ambient temperature, humidity, wind speed, and
radiant temperature combined into the universal thermal climate index. Additionally, a
meteorological station will be placed in the bedroom, while sensors measuring solar flux
will be installed outdoor on the windows and balcony. Participants will also carry two
bracelets for the measurement of physiological parameters (blood pressure, skin
temperature, galvanic skin response as a marker of sweating, and heart rate). As part of
the VF++ project, core temperature data will be additionally collected in a subsample of
participants (e.g., 20 participants). Personal thermal discomfort, well-being, and sleep
quality will be self-reported on the smartphone using the Eco Emo tracker application. An
a posteriori phone questionnaire will collect detailed information on heat-related
practices and health impacts over the observation period. Analyses of short-term effects
will use repeated measure models. Investigations of momentary objective heat stress as
the outcome will use statistical techniques for complex mixtures to handle the wide set
of exposures. Analyses of sleep quality, well-being, and physiological measures as the
outcomes will use two complementary designs: fixed-effect analyses of matched
observations in the warm and in the cooler periods for the same participants; and
participant-level fixed-effect analyses of pooled observations in the warm period.
H3Sensing brings together epidemiologists, urbanists, and climate scientists. As
research-to-policy translation, experts in urbanism involved in the project will
formulate concrete technical recommendations and will identify practical solutions (in a
pedagogical document of synthesis) to help urban actors willing to integrate
considerations related to urban heat islands in their urbanistic regulations, public
policies, and urban planning projects.