Associations of Endothelial Function and Air Temperature in Diabetic Individuals

Abstract

ISEE-0194 Background and Objective: Epidemiological studies consistently show that air temperature is associated with changes in cardiovascular morbidity and mortality. However, the biological mechanisms underlying the association remain largely unknown. As one index of endothelial function, flow-mediated dilatation (FMD) can be viewed as a “barometer” of vascular health. Therefore, the purpose of this study was to analyze the short-term effects air temperature on markers of endothelial function in diabetic patients. Methods: A prospective panel study was conducted on 22 people with diabetes in Chapel Hill, NC, from Nov 2004-Dec 2005. Each subject was studied for four consecutive days. Daily measurements of meteorological data were acquired from the rooftop of the patient exam site. FMD measured by brachial artery ultrasound as well as blood markers on endothelial function were assessed during each patient visit. Data were analyzed using random effects models adjusting for relative humidity, barometric pressure, and particles with an aerodynamic diameter <2.5μm, and day of the week. Results: FMD decreased in association with a 1°C decrease in temperature on the same day (percent-change in mean level:−4.2% with 95%-confidence interval (CI): [−6.9%; −1.4%]) as well as with a delay of one day (−3.3%; 95%-CI: [−6.5%; −0.1%]), four days (−3.4%; 95%-CI: [−6.3%; −0.5%]) and with the 5-day-average (−4.3%; 95%-CI: [−8.4%; −0.3%]). We also found an increase in intercellular adhesion molecules sICAM-1 in association with the 5-day-average of temperature (7.9%; 95%-CI: [2.0%; 13.8%]). A similar trend was seen for vascular cell adhesion molecules sVCAM-1. Other blood markers representing endothelial function such as von Willebrand factor and endothelial-leukocyte adhesion molecule E-selectin did not show any temperature effect. Conclusion: These data suggest that endothelial function is associated with short-term temperature changes. Endothelial dysfunction might contribute to the increase in cardiovascular morbidity and mortality associated with cold weather. This abstract of a proposed presentation does not necessarily represent EPA policy.