Long-Term Exposure to Fine Particulate Matter (PM_2.5) and Cardiovascular Disease Mortality among Renal Transplant Recipients

Background: Substantial evidence has established links between air pollution and increased risks of overall morbidity and mortality, especially for respiratory and cardiovascular diseases. However, little research has explored these relationships among highly sensitive populations, such as renal transplant recipients. Despite the improvement in quality of life after renal transplantation, cardiovascular diseases (CVD) are major causes of graft loss and mortality. The present study was designed to assess the association between long-term ambient fine particulate matter (PM_2.5) and risk of CVD-related mortality, including CHD, stroke, sudden cardiac arrest, and CHF, among renal transplant recipients. Methods: This retrospective cohort study consists of transplant data from 2001 to 2015, and includes 93,857 non-smoking, adult renal transplant recipients who have lived in the contiguous United States at the same location throughout the study period. Annual-average concentrations for the three ambient air pollutants (PM_2.5, O₃, and NO₂) were assigned to subjects’ residential ZIP codes. Cox proportional hazard models were used to assess the association between PM_2.5 and CVD mortality risk. Results: In the multivariable-adjusted models, a 10 ug/m³ increase in ambient PM_2.5 levels was associated with increased risk of total CVD (HR=1.85, 95 % CI: 1.57 – 2.17), CHD (HR=2.20, 95 % CI: 1.53 – 3.17), stroke (HR=1.82, 95%CI: 1.15 – 2.89), and cardiac arrest (HR=1.77, 95% CI: 1.42 – 2.19). There was no clear association between PM_2.5 and risk of CHF mortality. Conclusions: The findings of this study provide strong evidence supporting an adverse effect of ambient PM_2.5 in this vulnerable group. Positive associations were found between PM_2.5 and all CVD mortality outcomes, except CHF mortality. Our findings raise the question of whether increased emphasis should be placed on implementing preventive strategies to lessen the impact of air pollution on CVD risk.