Air pollution and lipid levels: Associations with particulate matter, traffic particles, and ozone in the va normative aging study
Wilker, E; Mittleman, M; Vokonas, P; Schwartz, J
Background: Exposure to ambient air pollution has been associated with cardiovascular effects including inflammation and atherosclerosis, but the underlying mechanisms are not well understood. We hypothesized that exposures to particulate matter<2.5 µm in diameter (PM2.5), black carbon (BC), and ozone would be associated with increased lipid levels in an elderly population and that these relationships would follow different patterns of association according to variation in pollutant composition.
Methods: We examined associations between lipid levels and ambient pollutants among participants in the Normative Aging Study using 1-4 week moving averages. Fasting serum samples were analyzed for total cholesterol, high density lipoprotein (HDL), triglycerides and (calculated) low density lipoprotein (LDL). Continuous PM2.5 and BC levels were measured 1 km from the exam site and ozone was averaged from four Boston-area monitors. We used Generalized Additive Mixed Models with random intercepts for each subject to account for between-subject variability. Individual pollutants models were adjusted for potential confounders including clinical characteristics, lifestyle and meteorological factors, and time trends. For ozone, cold and warm seasons were modeled separately to obtain effect estimates.
Results: Lipid levels and complete information on potential confounders were available for 914 participants. The mean total cholesterol, HDL, LDL and triglycerides were 200 ± 42 mg/dL, 47±13 mg/dL, 125±37 mg/dL, and 138±67.6 mg/dL respectively. We observed strong associations between BC and significant lower HDL, as well as higher LDL and total cholesterol/HDL ratios across all time points. A 1 SD change in the 2-week moving average of BC (0.38 µg/m^3) was associated with 2.1 mg/dL lower HDL levels (95% CI: -2.7, -1.6, p<.001), 3.2 mg/dL higher LDL levels (95% CI: 1.6, 4.9, p<.001), and a 0.24 change in the total cholesterol/HDL ratio (95% CI: 0.17, 0.31, p<.001). Similar but weaker associations were observed for PM2.5. We observed an association between ozone levels and lower HDL in the warm seasons. A 2-week moving average was associated with a 1.4 mg/dL lower HDL (95% CI: -2.2, -0.7, p<.001). No significant associations were observed for ozone in the cold seasons. Ozone associations remained significant when BC was included in the models.
Conclusions: We have demonstrated associations between air pollution, particularly traffic particles, and changes in lipid levels known to be risk factors for cardiovascular disease.
