Abstract
Background: Previous studies have shown that heatwaves are associated with increased mortality. However, it remains unclear whether the associations between heatwaves and mortality are modified by the environmental quality. Methods: We used the United States (US) Environmental Protection Agency’s Environmental Quality Index (EQI) and its five domain indices (air, water, land, built, and sociodemographic) to represent the cumulative environmental quality. We applied a time-stratified case-crossover design to analyze the disparities in the association between heatwaves and non-accidental deaths (NAD) among counties with different environmental qualities, in metropolitan areas in Alabama (AL), United States. Results: We found significant associations between heatwaves and NAD and a significant effect modification of this relationship by EQI. There were higher odds ratios in counties with the worst cumulative environmental qualities compared to counties with the best cumulative environmental qualities. For example, the percent change in odds ratio (mean and (95% CI)) between heatwave days and non-heatwave days was −10.3% (−26.6, 9.6) in counties with an overall EQI of 1 (the best overall environment) and 13.2% (4.9, 22.2) in counties with an overall EQI of 3 (the worst overall environment). Among the five domains, air quality had the strongest effect modification on the association. Conclusion: Our findings provide evidence that the associations between heatwaves and NAD vary among areas with different environmental qualities. These findings suggest that integration of air quality and heatwave warning systems may provide greater protection to public health.
Highlights
Numerous previous studies have reported increased mortality during heatwaves worldwide [1,2,3,4,5,6,7].the associations varied greatly across different locations
10 counties were classified in the overall Environmental Quality Index (EQI) 1
We focused our analysis on three indices previously shown to be associated with non-accidental death (NAD) and preterm birth in Alabama [4], to explore effect modifications by environmental quality characteristics
Summary
Numerous previous studies have reported increased mortality during heatwaves worldwide [1,2,3,4,5,6,7].the associations varied greatly across different locations. The estimated increase in mortality was about 3% at the national level for the United States (US), while regional increases in mortality on heatwave days compared to non-heatwave days, ranged from 1.84% to 6.76% [7]. Another study found that the increase in mortality in Europe during heat wave days ranged from 7.6% to 33.6% [8] Both individual and area-level factors have been used to explain variations in the associations between heatwaves and mortality. Previous studies have shown that heatwaves are associated with increased mortality It remains unclear whether the associations between heatwaves and mortality are modified by the environmental quality. We applied a time-stratified case-crossover design to analyze the disparities in the association between heatwaves and non-accidental deaths (NAD) among counties with different environmental qualities, in metropolitan areas in Alabama (AL), United States. The percent change in odds ratio (mean and (95% CI)) between heatwave days and non-heatwave days was
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