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Affiliation
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Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA. |
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Abstract
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BACKGROUND: In a changing climate, increasing temperatures are anticipated to have profound health impacts. These impacts could be mitigated if individuals and communities adapt to changing exposures; however, little is known about the extent to which the population may be adapting.
OBJECTIVE: To investigate the hypothesis that if adaptation is occurring, then heat-related mortality would be decreasing over time.
METHODS: We used a national database of daily weather, air pollution, and age-stratified mortality rates for 105 US cities (covering 106 million people) during the summers 1987-2005. Time-varying coefficient regression models and Bayesian hierarchical models were used to estimate city-specific, regional, and national temporal trends in heat-related mortality, and to identify factors that explain variation across cities.
RESULTS: On average across cities, the number of deaths (per 1000 deaths) attributable to each 10°F increase in same-day temperature decreased from 51 (95% posterior interval: 42-61) in 1987 to 19 (12-27) in 2005. This decline was largest among those 75 and older, in northern regions, and in cities with cooler climates. Though central air conditioning prevalence has increased, we did not find statistically significant evidence of larger temporal declines among cities with larger increases in prevalence.
CONCLUSIONS: The population has become more resilient to heat over time. Yet even with this increased resilience, substantial risks of heat-related mortality remain. Based on 2005 estimates, an increase in average temperatures by 5°F (central climate projection) would lead to an additional 1,907 deaths per summer across all cities.
Language: en |