Petkova, E.P., Gasparrini, A. and Kinney, P.L. 2014. Heat and mortality in New York City since the beginning of the 20th century. Epidemiology 25: 554-560.
Writing as background for their work, Petkova et al. (2014) note that "heat-related mortality has become a research topic of increasing importance as a result of increases in average temperature - as well as temperature extremes - owing to climate change," but they say that "few previous studies have assessed the impact of population adaptation to heat."
Going where few researchers had gone before, Petkova et al. "examined adaptation patterns by analyzing daily temperature and mortality data spanning more than a century in New York City," where using a distributed-lag nonlinear model they analyzed the heat-mortality relation in people 15 years of age or older during two periods: 1900-1948 and 1973-2006, in order to "quantify population adaptation to high temperatures over time."
The three researchers report that "during the first half of the century, the decade-specific relative risk of mortality at 29°C vs. 22°C ranged from 1.30 in the 1910s to 1.43 in the 1900s." Since 1973, however, they found "there was a gradual and substantial decline in the relative risk, from 1.26 in the 1970s to 1.09 in the 2000s." In addition, they say that "age-specific analyses indicated a greater risk for people of age 65 years and older in the first part of the century," but that "there was less evidence for enhanced risk among this older age group in more recent decades."
Petkova et al.'s discovery that the excess mortality originally experienced at high temperatures was substantially reduced over the course of the century they studied is indicative, in their words, of "population adaptation to heat in recent decades," which they attribute primarily to "the rapid spread and widespread availability of air conditioning." And this association suggests that as a people's standard of living rises, so too does their ability to survive in warmer climates increase, because with more wealth they can do more to reduce negative heat-induced impacts on human health.Reviewed 24 September 2014