A heat-health watch and warning system with extended season and evolving thresholds

Abstract

Background Many countries have developed heat-health watch and warning systems (HHWWS) or early-warning systems to mitigate the health consequences of extreme heat events. HHWWS usually focuses on the four hottest months of the year and imposes the same threshold over these months. However, according to climate projections, the warm season is expected to extend and/or shift. Some studies demonstrated that health impacts of heat waves are more severe when the human body is not acclimatized to the heat. In order to adapt those systems to potential heat waves occurring outside the hottest months of the season, this study proposes specific health-based monthly heat indicators and thresholds over an extended season from April to October in the northern hemisphere. Methods The proposed approach, an adoption and extension of the HHWWS methodology currently implemented in Quebec (Canada). The latter is developed and applied to the Greater Montreal area (current population 4.3 million) based on historical health and meteorological data over the years. This approach consists of determining excess mortality episodes and then choosing monthly indicators and thresholds that may involve excess mortality. Results We obtain thresholds for the maximum and minimum temperature couple (in °C) that range from (respectively, 23 and 12) in April, to (32 and 21) in July and back to (25 and 13) in October. The resulting HHWWS is flexible, with health-related thresholds taking into account the seasonality and the monthly variability of temperatures over an extended summer season. Conclusions This adaptive and more realistic system has the potential to prevent, by data-driven health alerts, heat-related mortality outside the typical July–August months of heat waves. The proposed methodology is general and can be applied to other regions and situations based on their characteristics.

Efficacy of Cooling Centers for Mitigating Physiological Strain in Older Adults during Daylong Heat Exposure: A Laboratory-Based Heat Wave Simulation

“…We opted to suspend testing in the summer because the health impacts of heat waves are more pronounced early in the summer, likely owing to a lack of natural acclimatization, 15 which occurs with seasonal elevations in heat exposure. 16 , 17 No testing was completed between March and November 2020 because of the COVID-19 pandemic.…”

Effects of Daylong Exposure to Indoor Overheating on Thermal and Cardiovascular Strain in Older Adults: A Randomized Crossover Trial

“… 78 Areas with higher mean summer temperatures experience smaller elevations in heat-related mortality during heat waves (defined based on local temperature thresholds) 79 due, in part, to physiological acclimatization. 30 – 32 Our study is therefore most applicable to public health agencies in Ontario and surrounding areas (e.g., Quebec, Canada, and the Midwest and Northeast regions of the United States). There is, however, indirect evidence that our findings may be generalizable to other geographical locations with continental and/or temperate climates.…”

“…This was done for the sake of ecological relevance since individuals regularly exposed to high summer temperatures (indoors and outdoors) gain some degree of natural acclimatization. 30 – 32 However, six participants completed their trials during late fall or winter because of disturbances stemming from COVID-19–related testing restrictions. Exposure simulations for each participant were separated by a minimum of 48 h. Most participants completed their exposures on the same weekday over four consecutive weeks ( ), resulting in a median 21 d between the first and final laboratory visit (min: 11 d, max: 35 d).…”

Explorative Assessment of the Temperature–Mortality Association to Support Health-Based Heat-Warning Thresholds: A National Case-Crossover Study in Switzerland

“…It is well known from multi-city and multi-country studies that the effects of a specific temperature on health can vary between regions because of the populations’ adaptation to the regional climate and their sensitivity to heat [ 7 , 10 , 25 ]. Some warning systems such as in Germany and Spain also consider different thresholds at the beginning and the end of the summer to account for the short-term adaptation to heat in the course of a summer [ 17 , 26 ].…”