The health impacts of exposure to summertime heat are a significant problem in New York City (NYC) and for many cities and are expected to increase with a warming climate. Most studies on heat-related mortality have examined risk factors at the municipal or regional scale and may have missed the intra-urban variation of vulnerability that might inform prevention strategies. We evaluated whether place-based characteristics (socioeconomic/demographic and health factors, as well as the built and biophysical environment) may be associated with greater risk of heat-related mortality for seniors during heat events in NYC. As a measure of relative vulnerability to heat, we used the natural cause mortality rate ratio among those aged 65 and over (MRR65+), comparing extremely hot days (maximum heat index 100°F+) to all warm season days, across 1997-2006 for NYC's 59 Community Districts and 42 United Hospital Fund neighborhoods. Significant positive associations were found between the MRR65+ and neighborhood-level characteristics: poverty, poor housing conditions, lower rates of access to air-conditioning, impervious land cover, surface temperatures aggregated to the area-level, and seniors' hypertension. Percent Black/African American and household poverty were strong negative predictors of seniors' air conditioning access in multivariate regression analysis.

Background: Heat is recognized as one of the deadliest weather-related phenomena. Although the impact of high temperatures on mortality has been a subject of extensive research, few previous studies have assessed the impact of population adaptation to heat. Methods: We examined adaptation patterns by analyzing daily temperature and mortality data spanning more than a century in New York City. Using a distributed-lag nonlinear model, we analyzed the heat-mortality relation in adults age 15 years or older in New York City during 2 periods: 1900–1948 and 1973–2006, to quantify population adaptation to high temperatures over time. Results: During the first half of the century, the decade-specific relative risk of mortality at 29°C vs. 22°C ranged from 1.30 (95% confidence interval [CI]= 1.25–1.36) in the 1910s to 1.43 (1.37–1.49) in the 1900s. Since the 1970s, however, there was a gradual and substantial decline in the relative risk, from 1.26 (1.22–1.29) in the 1970s to 1.09 (1.05–1.12) in the 2000s. Age-specific analyses indicated a greater risk for people age 65 years and older in the first part of the century, but there was less evidence for enhanced risk among this older age group in more recent decades. Conclusion: The excess mortality with high temperatures observed between 1900 and 1948 was substantially reduced between 1973 and 2006, indicating population adaption to heat in recent decades. These findings may have implications for projecting future impacts of climate change on mortality.

Rising temperatures may alter the proportions of both heat- and cold-related deaths, leaving the net impact on annual mortality uncertain. Current and future seasonal patterns of temperature-related mortality in Manhattan, New York, are estimated, showing warm season increases and cold season decreases in temperature-related mortality, with positive net annual deaths in all cases. Global average temperatures have been rising for the past half-century, and the warming trend has accelerated in recent decades1. Further warming is expected over the next few decades, with significant regional variations. These warming trends will probably result in more frequent, intense and persistent periods of hot temperatures in summer, and generally higher temperatures in winter. Daily death counts in cities increase markedly when temperatures reach levels that are very high relative to what is normal in a given location2,3,4. Relatively cold temperatures also seem to carry risk2,4. Rising temperatures may result in more heat-related mortality but may also reduce cold-related mortality, and the net impact on annual mortality remains uncertain. Here we use 16 downscaled global climate models and two emissions scenarios to estimate present and future seasonal patterns in temperature-related mortality in Manhattan, New York. All 32 projections yielded warm-season increases and cold-season decreases in temperature-related mortality, with positive net annual temperature-related deaths in all cases. Monthly analyses showed that the largest percentage increases may occur in May and September. These results suggest that, over a range of models and scenarios of future greenhouse gas emissions, increases in heat-related mortality could outweigh reductions in cold-related mortality, with shifting seasonal patterns.