Are air pollution and traffic noise independently associated with atherosclerosis: the Heinz Nixdorf Recall Study

Living close to high traffic has been linked to subclinical atherosclerosis, however it is not clear, whether fine particulate matter (PM) air pollution or noise, two important traffic-related exposures, are responsible for the association. We investigate the independent associations of long-term exposure to fine PM and road traffic noise with thoracic aortic calcification (TAC), a reliable measure of subclinical atherosclerosis. We used baseline data (20002003) from the German Heinz Nixdorf Recall Study, a population-based cohort of 4814 randomly selected participants. We assessed residential long-term exposure to PM with a chemistry transport model, and to road traffic noise using faade levels from noise models as weighted 24 h mean noise (L-den) and night-time noise (L-night). Thoracic aortic calcification was quantified from non-contrast enhanced electron beam computed tomography. We used multiple linear regression to estimate associations of environmental exposures with ln(TAC1), adjusting for each other, individual, and neighbourhood characteristics. In 4238 participants (mean age 60 years, 49.9 male), PM2.5 (aerodynamic diameter 2.5 m) and L-night are both associated with an increasing TAC-burden of 18.1 (95 CI: 6.6; 30.9) per 2.4 g/m(3) PM2.5 and 3.9 (95 CI 0.0; 8.0) per 5dB(A) L-night, respectively, in the full model and after mutual adjustment. We did not observe effect measure modification of the PM2.5 association by L-night or vice versa. Long-term exposure to fine PM and night-time traffic noise are both independently associated with subclinical atherosclerosis and may both contribute to the association of traffic proximity with atherosclerosis.