Association between Homelessness and Temperature-Related Health Emergencies in the United States

This is the authors' abstract. We don't add key points for this paper.

Temperature-related illness (TRI) encompasses heat-related illness, such as heat exhaustion and heatstroke, and cold-related illness, such as frostbite and hypothermia. TRI is typically the result of exposure to ambient weather conditions; because of this, unhoused individuals are hypothesized to have higher risk of TRI. However, no national epidemiological studies have been completed to determine this risk. The objective of this study was to determine the association between homelessness and emergency department (ED) diagnosis of TRI in the United States. We conducted a cross-sectional study of adult ED visits in the United States from 2005 through 2020 using data from the National Hospital Ambulatory Medical Care Survey (NHAMCS), a nationally representative sample of nonfederal ED patient visits. Housing status (housed versus unhoused) was measured using NHAMCS patient residence category, with blank responses excluded. TRI was defined as ED clinician diagnosis of heat- or cold-related illness using International Classification of Disease, versions 9 and 10 (ICD-9 and ICD-10) codes. Multivariable logistic regression was used to determine adjusted odds of TRI by housing status. There were 323 606 nonpediatric ED visits in the NHAMCS sample. TRI diagnosis was present in 288 (0.09%) visits. 4099 visits (0.9%) were categorized as unhoused. After adjusting for sex, mental health diagnosis, and alcohol or substance use or use disorder, the odds ratio of TRI diagnosis in unhoused individuals was 4.08 (95% CI 2.09, 7.95) compared to housed individuals. We found a higher adjusted odds ratio of TRI diagnosis at an ED visit among unhoused individuals compared with housed individuals. Significance Statement Temperature-related health emergencies, or illnesses caused by exposure to ambient weather conditions, affect numerous Americans each year and are expected to become more common as climate change continues. We wanted to understand whether unhoused individuals are at higher risk of these health emergencies. We used a national sample of emergency department visits in the United States to study this and found out that unhoused individuals are at more than four times the risk of these illnesses than housed individuals. Our work highlights the need for prevention of homelessness, stable housing for housing insecure populations, and heating and cooling centers during weather emergencies.