Changing heat impacts on mortality and implications for mitigation planning in New York City

Abstract

BACKGROUND AND AIM: Heat mitigation planning requires careful characterization of the adverse impacts of temperature on health outcomes. New York City (NYC) has used observed temperature-mortality relationships to revise the city’s heat advisory trigger threshold, but such assessment must be ongoing as temperatures rise. METHODS: We analyzed 5-year rolling periods of weather and mortality data for May-September, 1997-2017 in NYC to estimate changes in cumulative relative risks (CRR) with up to 3-day lag and attributable deaths over time using both the extreme heat event (EHE) day indicator (0/1) for NYC’s heat advisory threshold (=35°C for two days or =38°C for any duration) and a continuous daily maximum heat index (or maximum temperature when heat index was unavailable), or MAX, using quasi-Poisson distributed lag non-linear models. For MAX, we used the median for the entire period (28°C) as reference, estimated CRRs at 37°C (median temperature of days above 35°C), compared to EHE CRR, and estimated attributable deaths for all days above 28°C. RESULTS:CRRs for both EHE and MAX have been comparable and stable (~1.08) in the recent decade and lower than in earlier periods (~1.10). The number of EHE days were stable over the study period (~10 days/year), while non-EHE summer days (28°C to less than 35°C) have been increasing (57 days in 1997-2001 vs. 74 days in 2013-2017). The estimated attributable deaths for MAX mirror the warming climate, increasing since 1997, and surpassing those for EHE in recent years (267 MAX vs 94 EHE for 2013-2017). CONCLUSIONS:Estimated excess deaths due to non-EHE days are larger than those for EHE days and increasing. In NYC, where the overall air conditioning prevalence is greater than 90%, near-term heat mitigation should focus on addressing inequities in air conditioning and energy insecurity in the most-impacted communities along with other structural heat mitigation strategies beyond emergency response. KEYWORDS: temperature, mortality, extreme heat, attributable deaths, heat mitigation