LAUSR

Background: Heat‐related morbidity and mortality is a recognized public health concern. However, public health officials need to base policy decisions on local evidence, which is often lacking for smaller communities. Objectives: To evaluate the association between maximum daily heat index (HI) and morbidity and mortality in 15 New England communities (combined population: 2.7 million) in order to provide actionable evidence for local officials. Methods: We applied overdispersed Poisson nonlinear distributed lag models to evaluate the association between HI and daily (May‐September) emergency department (ED) admissions and deaths in each of 15 study sites in New Hampshire, Maine, and Rhode Island, controlling for time trends, day of week, and federal holidays. Site‐specific estimates were meta‐analyzed to provide regional estimates. Results: Associations (sometimes non‐linear) were observed between HI and each health outcome. For example, a day with a HI of 95°F vs. 75°F was associated with a cumulative 7.5% (95% confidence interval [CI]: 6.5%, 8.5%) and 5.1% (95% CI: 0.2%, 10.3%) higher rate of all‐cause ED visits and deaths, respectively, with some evidence of regional heterogeneity. We estimate that in the study area, days with a HI≥95°F were associated with an annual average of 784 (95% CI: 658, 908) excess ED visits and 22 (95% CI: 3, 39) excess deaths. Conclusions: Our results suggest the presence of adverse health impacts associated with HI below the current local guideline criteria of HI≥100°F used to issue heat advisories. We hypothesize that lowering this threshold may lead to substantially reduced heat‐related morbidity and mortality in the study area. HighlightsHeat‐related morbidity and mortality is a recognized public health concern.The local evidence needed to inform policy is often lacking for smaller communities.We found health impacts at heat index values below the current local guideline criteria used to issue heat advisories.Lowering the guideline criteria may lead to substantially fewer deaths and emergency department visits in New England.