With climate change, temperatures are increasing. Heat-associated health events disproportionately affect certain subpopulations. However, prior research has often lacked information on individual-level health and air conditioning and neighborhood stressors/protections.
To assess whether (1) heat (2-day mean temperature above local 75th percentiles) is associated with increased heart rate and decreased blood pressure, controlling for age, time, season, daily ozone, and daily particulate matter (PM2.5) and (2) associations differ by antihypertensive medication use, renal function, fasting glucose, emotional support, air conditioning ownership and use, normalized difference vegetation index, neighborhood safety, and residence- specific oxides of nitrogen and PM2.5.
Health and behavioral characteristics were obtained repeatedly on participants of the Multi-Ethnic Study of Atherosclerosis in six US sites (2000–2010). These were linked with airport temperature, air quality, and satellite- and survey-derived neighborhood characteristics. We used a fixed-effects design, regressing health outcomes on linear temperature splines with knots at the 75th percentiles, interaction terms for each characteristic, and adjustment for month of year, age, PM2.5, and ozone.
Overall, heat was not associated with heart rate. However, for a 2°C increase in heat, systolic blood pressure decreased by 1.1 mmHg (95% CI = −1.6, −0.6) and diastolic blood pressure by 0.3 mmHg (95% CI = −0.6, −0.1). Among nonusers of antihypertensive medications, heat-associated decreases in SBP were 2.1 mmHg greater among individuals with central air conditioning versus those without. Confidence intervals around the remaining modifiers were wide after multiple-comparisons corrections or sensitivity analyses.
Outdoor heat is associated with decreasing blood pressure, and cardiovascular vulnerability may vary primarily by ownership of central air conditioning.
From the aDepartment of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI
bDepartment of Environmental and Occupational Health Sciences, University of Washington School of Public Health, Seattle, WA
cDepartment of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, MI
dDepartment of Epidemiology and Biostatistics, Drexel University Dornsife School of Public Health, Philadelphia, PA
eRAND Corporation, Arlington, VA.
Submitted December 1, 2017; accepted July 27, 2018.
Data availability: The computing code may be obtained from the corresponding author on request. The data may be obtained from the MESA Coordinating Center after completion of a Data Distribution Agreement and review and approval of a detailed proposal by MESA Publications and Steering Committees for soundness in science, methodology, and adherence to MESA policy.
This research was funded by a University of Michigan Graham Sustainability Institute Dow Sustainability Fellowship; a Michigan Institute for Clinical and Health Research Postdoctoral Translational Scholars Program Fellowship (National Center for Advancing Translational Sciences [NCATS] grant UL1TR000433); the NIOSH Education and Research Center at University of Michigan (T42 OH008455-09); the Michigan Center for the Study of Lifestage Exposures and Adult Disease (P30 ES017885); and National Science Foundation grant 1520803. This research was supported by contracts HHSN268201500003I, N01-HC-95159, N01-HC-95160, N01-HC-95161, N01-HC-95162, N01-HC-95163, N01-HC-95164, N01-HC-95165, N01-HC-95166, N01-HC-95167, N01-HC-95168, and N01-HC-95169 from the National Heart, Lung, and Blood Institute and by grants UL1-TR-000040, UL1-TR-001079, and UL1-TR-001420 from NCATS. This publication was developed under a Science to Achieve Results (STAR) research assistance agreement number RD831697 (MESA Air), awarded by the US Environmental Protection Agency (EPA). It has not been formally reviewed by the EPA. The views expressed in this document are solely those of the authors and the EPA does not endorse any products or commercial services mentioned in this publication.
The authors report no conflicts of interest.
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Correspondence: Carina J. Gronlund, Center for Social Epidemiology and Population Health, University of Michigan School of Public Health, 2663 SPH Tower, 1415 Washington Heights, Ann Arbor, MI 48109. E-mail: firstname.lastname@example.org.