BACKGROUND: Epidemiological evidence on the influence of long-term exposure to traffic-related particulate matter (TPM(10)) on heart rate variability (HRV) is weak. OBJECTIVE: To evaluate the association of long-term exposure (10鈥痽ears) with TPM(10) on the regulation of the autonomic cardiovascular system and heart rate dynamics (HRD) in an aging general population, as well as potential modifying effects by the a priori selected factors sex, smoking status, obesity, and gene variation in selected glutathione S-transferases (GSTs). METHODS: We analyzed data from 1593 SAPALDIA cohort participants aged鈥?/=鈥?0鈥痽ears. For each participant, various HRV and HRD parameters were derived from 24-hour electrocardiogram recordings. Each parameter obtained was then used as the outcome variable in multivariable mixed linear regression models in order to evaluate the association with TPM(10). Potential modifying effects were assessed using interaction terms. RESULTS: No association between long-term exposure to TPM(10) and HRV/HRD was observed in the entire study population. However, HRD changes were found in subjects without cardiovascular morbidity and both HRD and HRV changes in non-obese subjects without cardiovascular morbidity. Subjects without cardiovascular morbidity with homozygous GSTM1 gene deletion appeared to be more susceptible to the effects of TPM(10). CONCLUSION: This study suggests that long-term exposure to TPM(10) triggers adverse changes in the regulation of the cardiovascular system. These adverse effects were more visible in the subjects without cardiovascular disease, in whom the overall relationship between TPM(10) and HRV/HRD could not be masked by underlying morbidities and the potential counteracting effects of related drug treatments.