The mortality burden of extreme heat in Connecticut: A time series analysis

Local epidemiological evidence is imperative for making state and regional policy decisions addressing climate change, especially considering geographic variability in temperature and acclimatization. While the health impacts of extreme heat have been quantified in broad contexts, greater research is needed to provide accurate and precise health impact estimates on local scales where climate action is likely. The re-establishment of Connecticut’s Governor’s Council on Climate Change and its formation of an Office of Climate Change and Public Health demonstrate Connecticut’s commitment to and readiness for climate change planning and adaptation. Using data on daily all-cause mortality and average temperature across Connecticut during the warm season from 2005–2016, we estimated the total mortality burden of extreme heat (defined as temperatures above the 90 th percentile, 24.7°C, and 99 th percentile, 27.4°C during the warm season) in Connecticut compared to the reference temperature (41.5 th percentile, 18.9°C). We conducted a time-series analysis using a generalized linear model with a quasi-Poisson regression, adjusting for the day of the week, holidays, and long-term trend. We found a statistically significant positive association between extreme heat and all-cause mortality, with a relative risk of 1.021 (95% CI: 1.002,1.041) at the 90 th warm season temperature percentile and 1.039 (95% CI: 1.009,1.071) at the 99 th warm season temperature percentile. We estimated that 31 deaths or 0.28% of all warm season deaths (95% eCI: 9, 53 or 0.08%, 0.48%) were attributable to extreme heat above the 90 th warm season temperature percentile in Connecticut each year, more than five times what is reported in the Global Burden of Disease 2019 study. These results support state-wide action to mitigate the negative health effects of extreme heat and further research to understand the specific causes behind and modifiers of heat-related mortality in localized contexts in Connecticut and elsewhere.