Relation of long-term exposure to air pollution to brachial artery flow-mediated dilation and reactive hyperemia

Long-term exposure to ambient air pollution has been associated with cardiovascular morbidity and mortality. Impaired vascular responses may, in part, explain these findings, but the association of such long-term exposure with measures of both conduit artery and microvascular function has not been widely reported. We evaluated the association between residential proximity to a major roadway (primary or secondary highway) and spatially resolved average fine particulate matter (PM_2.5) and baseline brachial artery diameter and mean flow velocity, flow-mediated dilation%, and hyperemic flow velocity, in the Framingham Offspring and Third Generation Cohorts. We examined 5,112 participants (2,731 [53%] women, mean age 49 ± 14 years). Spatially resolved average PM_2.5 was associated with lower flow-mediated dilation% and hyperemic flow velocity. An interquartile range difference in PM_2.5 (1.99 μg/m³) was associated with -0.16% (95% confidence interval [CI] -0.27%, -0.05%) lower flow-mediated dilation% and -0.72 (95% CI -1.38, -0.06) cm/s lower hyperemic flow velocity%. Residential proximity to a major roadway was negatively associated with flow-mediated dilation%. Compared with living ≥400 m away, living <50 m from a major roadway was associated with 0.32% lower flow-mediated dilation (95% CI -0.58%, -0.06%), but results for hyperemic flow velocity had wide confidence intervals -0.68 cm/s (95% CI -2.29, 0.93). In conclusion, residential proximity to a major roadway and higher levels of spatially resolved estimates of PM_2.5 at participant residences are associated with impaired conduit artery and microvascular function in this large community-based cohort of middle-aged and elderly adults.