Ambient Fine Particulate Matter, Outdoor Temperature and Risk of Metabolic Syndrome

Abstract

Introduction: Ambient air pollution and temperature have been linked with cardiovascular morbidity and mortality. Metabolic syndrome and its components—abdominal obesity, elevated fasting blood glucose, low high-density lipoprotein cholesterol, hypertension and hypertriglyceridemia—predict cardiovascular disease, but the environmental causes are understudied. This study prospectively examined the long-term associations of air pollution, defined as fine-particulate matter with diameter ≤2.5µm (PM2.5), and temperature on the development of metabolic syndrome and its components. Methods: Using covariate-adjusted Cox-models, we estimated associations of annual mean PM2.5 and temperature with incident risk of metabolic dysfunctions in 587 elderly Normative Aging Study men (mean (SD), 70 (7) years) between 1993-2011. Results: A 1-μg/m3 annual PM2.5 increase was associated with higher risk of developing metabolic syndrome (Hazard ratio [HR]=1.27, 95% Confidence Interval (CI): 1.06, 1.52), elevated fasting blood glucose (HR=1.20, 95%CI: 1.03, 1.39) and hypertriglyceridemia (HR=1.14, 95%CI:1.00, 1.30). Metabolic syndrome and high fasting blood glucose findings remained significant in PM2.5 levels below the U.S. Environmental Protection Agency’s limit (12-μg/m3). A 1-Cº annual temperature increase was associated with greater elevated fasting blood glucose risk (HR=1.33, 95%CI: 1.14, 1.56). Conclusions: Men living in neighborhoods with worse air quality—i.e., with higher PM2.5 levels and/or warmer than average—showed increased risk of developing metabolic dysfunctions.