Decadal changes in heat-related human mortality in the eastern United States

One hypothesized impact of climate warming is higher human mortality rates in the warm season, due to increasingly hot and/or humid conditions. On days with high afternoon apparent temperatures, we compared changes in daily mortality rates over 4 decades in 6 major metropolitan areas along a north-south transect in the eastern US. In the 3 southernmost cities examined, we found few significant weather-mortality relationships for any decade or demographic group. But in the 3 northern cities, we determined that statistically significant declines in population-adjusted mortality rates occurred between 1964 and 1994 for the total population and the white and elderly demographic subgroups during hot and humid weather. These statistically significant reductions in hot-weather mortality rates suggest that the populace in cities that were weather-sensitive in the 1960s and 1970s have become less impacted by extreme conditions over time because of improved medical care, increased access to air conditioning, and biophysical and infrastructural adaptations. This analysis counters the paradigm of increased heat-related mortality rates in the eastern US predicted to result from future climate warming.