Current and Projected Heat-Related Morbidity and Mortality in Rhode Island

Abstract

Background: Climate change is expected to cause increases in heat-related mortality, especially among the elderly and very young. However, additional studies are needed to clarify the effects of heat on morbidity across all age groups and across a wider range of temperatures.

Objectives: We aimed to estimate the impact of current and projected future temperatures on morbidity and mortality in Rhode Island.

Methods: We used Poisson regression models to estimate the association between daily maximum temperature and rates of all-cause and heat-related emergency department (ED) admissions and all-cause mortality. We then used downscaled Coupled Model Intercomparison Project Phase 5 (CMIP5; a standardized set of climate change model simulations) projections to estimate the excess morbidity and mortality that would be observed if this population were exposed to the temperatures projected for 2046-2053 and 2092-2099 under two representative concentration pathways (RCP): RCP 8.5 and 4.5.

Results: Between 2005 and 2012, an increase in maximum daily temperature from 75 to 85°F was associated with 1.3% and 23.9% higher rates of all-cause and heat-related ED visits, respectively. The corresponding effect estimate for all-cause mortality from 1999 through 2011 was 4.0%. The association with all-cause ED admissions was strongest for those < 18 or ≥ 65 years of age, whereas the association with heat-related ED admissions was most pronounced among 18- to 64-year-olds. If this Rhode Island population were exposed to temperatures projected under RCP 8.5 for 2092-2099, we estimate that there would be 1.2% (range, 0.6-1.6%) and 24.4% (range, 6.9-41.8%) more all-cause and heat-related ED admissions, respectively, and 1.6% (range, 0.8-2.1%) more deaths annually between April and October.

Conclusions: With all other factors held constant, our findings suggest that the current population of Rhode Island would experience substantially higher morbidity and mortality if maximum daily temperatures increase further as projected.

Citation: Kingsley SL, Eliot MN, Gold J, Vanderslice RR, Wellenius GA. 2016. Current and projected heat-related morbidity and mortality in Rhode Island. Environ Health Perspect 124:460-467; http://dx.doi.org/10.1289/ehp.1408826.

Figure 1

Natural spline fit showing the association between same-day maximum temperature and relative rate of all-cause (A) and heat-related (B) ED admissions in April–October 2005–2012 in Rhode Island. Maximum temperature was modeled using a natural cubic spline with 3 degrees of freedom and adjusted for day of week, federal holidays, O₃, dew point (natural spline with 3 degrees of freedom), and temporal trends and seasonality (using a natural spline with 5 degrees of freedom per year). The dashed lines represent 95% CIs, and the p-value shown corresponds to the overall p-value comparing by ANOVA the full model to the same model without any terms for temperature.

Figure 2

Natural cubic spline fit showing the association between same-day maximum temperature and relative rate of ED admissions for cardiovascular diseases (A), respiratory diseases (B), renal diseases (C), and acute renal failure (D) in Rhode Island, April–October 2005–2012. The modeling approach was analogous to that described in Figure 1. The dashed lines represent 95% CIs, and the p-value shown corresponds to the overall p-value comparing by ANOVA the full model to the same model without any terms for temperature.

Figure 3

Natural cubic spline fit showing the association between same-day maximum temperature and relative rate of all-cause mortality in Rhode Island, April–October 1999–2011. The curved dashed lines represent 95% CIs, the horizontal dashed line indicates RR = 1.00, and the p-value shown corresponds to the overall p-value comparing by ANOVA the full model to the same model without any terms for temperature.

Figure 4

Box and whisker plot depicting the relative change in all-cause ED admissions (A), heat-related ED admissions (B), and deaths (C) projected to occur annually between April and October if the Rhode Island population of 2005–2012 were exposed to the maximum temperatures projected for 2046–2053 and 2092–2099 under two emissions scenarios. The heavy horizontal line in each box denotes the median, the limits of each box denote the 25th and 75th percentiles, and the whiskers denote the minimum and maximum of the estimates derived from the 42 models for RCP 4.5 and of the 41 models for RCP 8.5.

Figure 5

Box and whisker plots depicting the absolute change in all-cause ED admissions (A), heat-related ED admissions (B), and deaths (C) projected to occur annually between April and October if the Rhode Island population of 2005–2012 were exposed to the maximum temperatures projected for 2046–2053 and 2092–2099 under two emissions scenarios.