Long-term exposure to traffic-related PM10 and decreased heart rate variability: Is the association restricted to subjects taking ACE inhibitors?

Abstract

BackgroundAlterations in heart rate variability (HRV) are a potential link between exposure to traffic-related air pollution and cardiovascular mortality. ObjectivesWe investigated whether long-term exposure to traffic-related PM10 (TPM10) is associated with HRV in older subjects and/or in participants taking specific cardiovascular treatment or with self-reported heart disease. MethodsWe included 1607 subjects from the general population aged 50 to 72years. These participants from the SAPALDIA cohort underwent ambulatory 24-hr electrocardiogram monitoring. Associations of average annual exposure to TPM10 over 10years with HRV parameters from time and frequency domains were estimated using multivariable mixed linear models. Effect estimates are expressed as percent changes in geometric means. ResultsHRV was only associated with TPM10 in participants under ACE inhibitor therapy (N=94). A 1μg/m3 increment, approximately equivalent to an interquartile range, in 10year average TPM10 was associated with decrements of 14.5% (95% confidence interval (CI), −25.9 to −1.3) in high frequency (HF) power, of 4.5% (−8.2 to −0.5) in the standard deviation of all normal-to-normal RR intervals (SDNN), of 10.6% (−18.5 to −1.9) in total power (TP) and an increase of 9.2% (0.8 to 20.2) in the LF/HF power ratio. ConclusionsIn the absence of an overall effect our results suggest that alterations in HRV, a measure of autonomic control of the cardiac rhythm, may not be a central mechanism by which long-term exposure to TPM10 increases cardiovascular mortality. Novel evidence on an effect in persons under ACE inhibitor treatment needs to be confirmed in future studies.