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

Abstract

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. 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. 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). 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