"Thermal Indices for Assessing the Impact of Outdoor Thermal Environments on Human Health: A Systematic Review of Observational Studies."
with K. Pantavou, A. Fillon, Z. Maniadis, and G. Nikolopoulos
Background The global rise in temperatures contributes to the increase of climate-sensitive diseases. Despite mitigation efforts, temperatures are projected to keep rising, highlighting the need for integrated methods to assess the impact of thermal environments on human health. Thermal indices quantify the effects of environment on health by considering various meteorological factors. This study summarizes the existing evidence on the association between thermal indices and health outcomes.
Methods Medline, Scopus, and Web of Science were systematically searched from inception until December, 2023 for observational studies examining the association between thermal indices and health outcomes in outdoor environments (protocol registration: PROSPERO CRD42023412470). Quality was assessed using the NIH Quality Assessment Tool.
Findings The search identified 5034 records, with 310 meeting eligibility criteria and examining 1143 associations. These associations represented 51 countries, primarily in North America (n=448, 39.2%) and Europe (n=399, 34.9%). Temperate climates (n=597, 52.2%) and warm thermal conditions (n=547, 47.9%) were the most frequently examined. Seventeen indices were identified, with Apparent Temperature being the most common (141 publications, 634 associations). Frequently used indices included also Heat Index (n=60), Universal Thermal Climate Index (n=42), and Physiologically Equivalent Temperature (n=39). About half of the associations focused on mortality (n=602, 52.7%) and half on morbidity (n=541, 47.3%) covering 18 categories of the International Classification of Diseases (ICD-11). The most frequently examined associations were for diseases of the circulatory system (n=304, 26.6%), all- cause morbidity/mortality (n=288, 25.2%), and diseases of the respiratory system (n=151, 13.2%). Among warm thermal conditions (n=882), 57.8% (n=510) suggested an increased risk of adverse health outcomes as indices increased, while in cool conditions (n=367), 44.1% (n=162) suggested an increased risk as indices decreased.
Interpretation This systematic review reveals significant associations between thermal indices and health outcomes, indicating that thermal indices could be valuable tools for public health planning. However, the diversity in methodologies across studies highlights the need for standardization.
Funding This work was conducted in the context of “SInnoPSis” project funded by the Horizon 2020 under grant agreement ID: 857636