The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in California

Lack of access to cool spaces is considered to be a key determinant of heat vulnerability. However, assessments of the moderating effect of access to cooling on heat health outcomes have typically used spatially coarse estimates of residential air conditioning (AC) prevalence. Here we estimate patte...

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Main Authors: Yasmin Romitti, Ian Sue Wing, Keith R. Spangler, Gregory A. Wellenius
Format: Article
Language:English
Published: Elsevier 2025-08-01
Series:Environment International
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Online Access:http://www.sciencedirect.com/science/article/pii/S0160412025004106
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author Yasmin Romitti
Ian Sue Wing
Keith R. Spangler
Gregory A. Wellenius
author_facet Yasmin Romitti
Ian Sue Wing
Keith R. Spangler
Gregory A. Wellenius
author_sort Yasmin Romitti
collection DOAJ
description Lack of access to cool spaces is considered to be a key determinant of heat vulnerability. However, assessments of the moderating effect of access to cooling on heat health outcomes have typically used spatially coarse estimates of residential air conditioning (AC) prevalence. Here we estimate patterns of inter- and intra-urban AC ownership across 1,582 zip code tabulation areas (ZCTAs) in 27 California cities, use the results to assess the covariation between AC and social vulnerability, and examine how AC prevalence and social vulnerability modify the association between extreme heat and morbidity. Our approach combines Census records, the CDC Social Vulnerability Index (SVI), meteorological variables, and hospital admissions across the 2012–2019 warm season from the California Department of Health Care Access and Information. We first construct individual- and ZCTA-level estimates of residential AC prevalence, which we then compare with SVI between and within metro areas, and separately assess their effect modification on all-cause and cause-specific morbidity using a space–time-stratified case-crossover design with conditional Poisson regression models. We found that AC prevalence is weakly positively correlated with social vulnerability (r = 0.15) across the state and weakly negatively correlated within cities (r = −0.25). We found evidence of effect modification from AC prevalence on associations between extreme heat and all-cause (RR 1.04 (1.03, 1.05) for low AC versus RR 1.01 (1.00, 1.02) for high AC) as well as some cause-specific hospitalizations (e.g., heat-related illness: RR 1.42 (1.32, 1.52) for low AC versus 1.21 (1.11, 1.32) for high AC). Importantly, we find that residential AC reduces – but does not eliminate – the risks of adverse heat health outcomes.
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spelling doaj-art-71fe7ad26ff0413da6d1dda2d202fedd2025-08-20T03:50:21ZengElsevierEnvironment International0160-41202025-08-0120210965910.1016/j.envint.2025.109659The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in CaliforniaYasmin Romitti0Ian Sue Wing1Keith R. Spangler2Gregory A. Wellenius3Department of Earth and Environment, Boston University, 685 Commonwealth Ave, Boston, MA 02215, USA; Center for Climate and Health, Boston University, 715 Albany Street, Boston, MA 02118, USA; Health Effects Institute, 75 Federal Street, Suite 1400, Boston, MA 02110-1940, USA; Department of Environmental Health, Boston University School of Public Health, 715 Albany Street, Boston, MA 02118, USA; Corresponding author at: Commonwealth Avenue, Boston, MA 02215, USA.Department of Earth and Environment, Boston University, 685 Commonwealth Ave, Boston, MA 02215, USA; Center for Climate and Health, Boston University, 715 Albany Street, Boston, MA 02118, USACenter for Climate and Health, Boston University, 715 Albany Street, Boston, MA 02118, USA; Department of Environmental Health, Boston University School of Public Health, 715 Albany Street, Boston, MA 02118, USA; Sargent College of Health & Rehabilitation Sciences, Boston University, 635 Commonwealth Ave, Boston, MA 02215, USACenter for Climate and Health, Boston University, 715 Albany Street, Boston, MA 02118, USA; Department of Environmental Health, Boston University School of Public Health, 715 Albany Street, Boston, MA 02118, USALack of access to cool spaces is considered to be a key determinant of heat vulnerability. However, assessments of the moderating effect of access to cooling on heat health outcomes have typically used spatially coarse estimates of residential air conditioning (AC) prevalence. Here we estimate patterns of inter- and intra-urban AC ownership across 1,582 zip code tabulation areas (ZCTAs) in 27 California cities, use the results to assess the covariation between AC and social vulnerability, and examine how AC prevalence and social vulnerability modify the association between extreme heat and morbidity. Our approach combines Census records, the CDC Social Vulnerability Index (SVI), meteorological variables, and hospital admissions across the 2012–2019 warm season from the California Department of Health Care Access and Information. We first construct individual- and ZCTA-level estimates of residential AC prevalence, which we then compare with SVI between and within metro areas, and separately assess their effect modification on all-cause and cause-specific morbidity using a space–time-stratified case-crossover design with conditional Poisson regression models. We found that AC prevalence is weakly positively correlated with social vulnerability (r = 0.15) across the state and weakly negatively correlated within cities (r = −0.25). We found evidence of effect modification from AC prevalence on associations between extreme heat and all-cause (RR 1.04 (1.03, 1.05) for low AC versus RR 1.01 (1.00, 1.02) for high AC) as well as some cause-specific hospitalizations (e.g., heat-related illness: RR 1.42 (1.32, 1.52) for low AC versus 1.21 (1.11, 1.32) for high AC). Importantly, we find that residential AC reduces – but does not eliminate – the risks of adverse heat health outcomes.http://www.sciencedirect.com/science/article/pii/S0160412025004106AdaptationAir conditioningHeat health vulnerability
spellingShingle Yasmin Romitti
Ian Sue Wing
Keith R. Spangler
Gregory A. Wellenius
The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in California
Environment International
Adaptation
Air conditioning
Heat health vulnerability
title The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in California
title_full The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in California
title_fullStr The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in California
title_full_unstemmed The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in California
title_short The effects of residential air conditioning and social vulnerability on heat-related hospitalizations in California
title_sort effects of residential air conditioning and social vulnerability on heat related hospitalizations in california
topic Adaptation
Air conditioning
Heat health vulnerability
url http://www.sciencedirect.com/science/article/pii/S0160412025004106
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