Impact of Stress and Traffic-Related Air Pollution on Heart Rate Variability and Cardiac Function in Rats

Introduction: Cardiovascular disease disproportionately impacts persons of lower socioeconomic position. This health disparity stem, in part, from disproportionate exposures to environmental pollution (traffic-related air pollution, TRAP) and chronic psychosocial stress. Understanding the interaction between the environment and social stress is key to addressing modifiable risk factors behind cardiovascular health. In this study, we hypothesized that prior exposure to chronic mild unpredictable stress (CMUS) makes the heart more vulnerable to adverse effects of realistic low-level TRAP exposure. Methods: We recorded electrocardiogram with telemetry from 38 Sprague Dawley rats for heart rate variability (HRV) analysis in the time domain. Stress groups were exposed to CMUS (random order of strobe light, loud noise, crowding, shaker, cage tilting, and no bedding) twice daily for three weeks. TRAP groups were exposed to real-time non-transformed TRAP from the Caldecott Tunnel during weeks 2&3. At the end of the exposure period, rats underwent echocardiographic assessment to evaluate cardiac function. Results: Exposure to CMUS alone reduced overall and long-term HRV, as evidenced by a 17% and 20% reduction in SDNN and SDANN, respectively (p < 0.05). TRAP significantly reduced SDNN (12%) regardless of whether the rats experienced stress (p < 0.05). Furthermore, SDANN showed a greater reduction in the CMUS+TRAP group compared to the TRAP alone group (p < 0.05). Echocardiographic assessments revealed a decline in fractional shortening after TRAP exposure regardless of stress status (p < 0.05), suggesting a reduced systolic function. There was no difference in E/A ratio, Isovolumetric contraction and relaxation times, indicating no change in diastolic function. Conclusion: These findings suggest that stress leads to a reduction in long-term HRV, and TRAP exposure exacerbates this decline. Additionally, TRAP exposure manifests as systolic dysfunction, however, these effects are not influenced by prior exposure to stress. These results highlight the significant impact of stress and realistic level of TRAP on cardiac health and could provide valuable insights into addressing disparities in cardiovascular disease among vulnerable populations. R01ES033472-01A1 & P30 ES023513 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.