Vulnerability to the Cardiovascular Effects of Ambient Heat in Six U.S. Cities: Results from the Multi-Ethnic Study of Atherosclerosis (MESA)

摘要

Background: 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 (AC) and neighborhood stressors/protections. Objectives: To assess whether 1) heat (two-day mean temperature above the local 75th percentile), 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 anti-hypertensive-medication use, renal function, fasting glucose, emotional support, AC ownership and use, normalized difference vegetation index, neighborhood safety and residence-specific oxides-of-nitrogen and PM2.5 exposure. Methods: Health and behavioral characteristics were obtained repeatedly on participants of the Multi-Ethnic Study of Atherosclerosis in six U.S. sites (2000-2010). These were linked with airport temperature, air quality, and satellite-and survey-derived neighborhood characteristics. We used an fixed-effects design, regressing health outcomes on linear temperature splines with knots at the city-specific 75th percentiles, interaction terms for each characteristic, and adjustment for month-of-year, age, PM2.5 and ozone. Results: For a 2-degree-Celsius increase in heat, systolic blood pressure (SBP) 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 individuals not using anti-hypertensive medications, heat-associated decreases in SBP were 2.1 mmHg greater among individuals with central AC vs. without. The remaining modifiers were not significant after multiple-comparisons corrections or in sensitivity analyses. Conclusions: Outdoor heat is associated with decreasing blood pressure, and cardiovascular vulnerability may vary primarily by central AC ownership.