New approach to identifying proper thresholds for a heat warning system using health risk increments

Abstract

Background: A critical adaptation strategy for reducing heat-related health risk under climate change is to establish a heat warning system with a proper threshold that requires evaluation of heat-health relationships using empirical data. Objectives: This work presents a new approach to selecting proper health-based thresholds for a heat warning system which are different from thresholds of heat-health relationship. Methods: The proposed approach examined heat-health relationships through analyzing 15 years of health records with a modified generalized additive model (GAM), compared risk ratio increments (RRIs) of threshold candidates against a reference, assessed frequency of days above these candidates, and presented results graphically for easy communication. The candidate with the maximum RRI and proper occurring frequency is potentially the best threshold. Three heat indicators, including wet-bulb globe temperature (WBGT), temperature (T), and apparent temperature (AT), as well as three health outcomes, including all-cause mortality, heatrelated hospital admissions, and heat-related emergency visits were evaluated. Results: Risk ratios for all three health outcomes showed a consistent rising trend with increasing threshold candidates for all three heat indicators among different age and gender groups. WBGT had the most obvious increasing trend of RRIs with the three health outcomes. The maximum RRI was observed in heat-related emergency visits (242%), followed by heat-related hospital admissions (73%), and all-cause mortality (9%). The RRIs assessed for the three health outcomes pointed to the same thresholds, 33.0°C, 34.0°C, and 37.5°C for WBGT, T, and AT, respectively. The number of days above these thresholds and for warning to be issued ranged between 0 and 7 days during 2000-2014. Discussion: This study demonstrated a new approach to determining heat-warning thresholds with different heat indicators and health outcomes. The proposed approach provides a straightforward, feasible, and flexible scientific tool that assists the authorities around the world in selecting a proper threshold for a heat warning system.

The Association of Social Distancing, Population Density, and Temperature with the SARS-CoV-2 Instantaneous Reproduction Number in Counties Across the United States

“…Wet-bulb temperatures are a metric that capture the thermodynamic relationship of temperature and humidity and have been applied in the study of weather and human mortality and other human disease. 7,8 These measurements were obtained from National Oceanic and Atmospheric Administration (NOAA) Local Climatological Data.…”

Association of Social Distancing, Population Density, and Temperature With the Instantaneous Reproduction Number of SARS-CoV-2 in Counties Across the United States

“…10,11 For this reason, the primary weather variable we used was wet-bulb temperature, a metric that captures the complex thermodynamic relationship of temperature and humidity, has been shown to predict human health events with more precision than temperature and humidity separately, and avoids the associated problem of collinearity. 12,13 Wet-bulb temperatures were obtained from the National Oceanic and Atmospheric Administration Local Climatological Data.…”

Using GAM regression analysis to identify proper heat-warning thresholds: a population-based observational study

“…The tens of thousands of deaths during the heat waves in India and Pakistan in 2015 further revealed that an effective heat warning system is even more critical in developing countries where health care systems lagged behind those in developed countries (7,8). While a heat warning system has long been recognized as the most effective way to reduce heat-related health risks (9,10), the challenge remains in selecting a proper heat indicator and an appropriate threshold with sound scientific evidences (11), which could trigger adequate responsive actions from the authorities to prevent high casualty and advise people for self-protection. This paper aims at providing a systematic approach to assisting authorities worldwide in identifying appropriate heat-warning thresholds.…”