Long- and short-term air pollution exposure and measures of arterial stiffness in the Framingham Heart Study

Abstract

Background: Studies of air pollution exposure and arterial stiffness have reported inconsistent results and large studies employing the reference standard of arterial stiffness, carotid-femoral pulse-wave velocity (CFPWV), have not been conducted.

Aim: To study long-term exposure to ambient fine particles (PM_2.5), proximity to roadway, and short-term air pollution exposures in relation to multiple measures of arterial stiffness in the Framingham Heart Study.

Methods: We assessed central arterial stiffness using CFPWV, forward pressure wave amplitude, mean arterial pressure and augmentation index. We investigated long-and short-term air pollution exposure associations with arterial stiffness with linear regressions using long-term residential PM_2.5 (2003 average from a spatiotemporal model using satellite data) and proximity to roadway in addition to short-term averages of PM_2.5, black carbon, particle number, sulfate, nitrogen oxides, and ozone from stationary monitors.

Results: We examined 5842 participants (mean age 51 ± 16, 54% women). Living closer to a major roadway was associated with higher arterial stiffness (0.11 m/s higher CFPWV [95% CI: 0.01, 0.22] living <50 m vs 400 ≤ 1000 m). We did not observe association between arterial stiffness measures and long-term PM_2.5 or short-term levels of PM_2.5, particle number, sulfate or ozone. Higher levels of black carbon and nitrogen oxides in the previous days were unexpectedly associated with lower arterial stiffness.

Conclusions: Long-term exposure to PM_2.5 was not associated with arterial stiffness but positive associations with living close to a major road may suggest that pollutant mixtures very nearby major roads, rather than PM_2.5, may affect arterial stiffness. Furthermore, short-term air pollution exposures were not associated with higher arterial stiffness.

Keywords: Air pollution; Applanation tonometry; Arterial stiffness; Epidemiology.

Figure 1.

Long-term PM_2.5 exposure at residential address in 2003 and residential proximity to major roadway and measures of arterial stiffness. Associations with arterial stiffness measures were scaled to the interquartile range in 2003 (1.46 μg/m³) of PM_2.5, 75^th (400 m) to the 25^th (50 m) centile of the log-transformed residential proximity to a major roadway and as categorical variable for residential proximity to major roadway using the residences between 400 m and less than or equal to 1000 m as the reference category.

Figure 2.

Short-term exposures to air pollution and measures of arterial stiffness. Associations expressed as a change in unit of outcome per 5 μg/m³ PM_2.5, 0.4 μg/m³ black carbon (BC), 15000 particles/cm³ (PN), 2 μg/m³ sulfate (SO₄^2-) 0.01 parts per million nitrogen oxides (NO_x), and 0.01 parts per million ozone (O₃).