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Background: Long-term exposure to fine particulate matter (PM_2.5) has been associated with increased mortality in the general US population and has been shown to negatively affect renal function. Kidney transplant recipients may be especially vulnerable to the effects of air pollution. Our objective was to investigate associations of PM_2.5 concentrations with mortality among US kidney transplant recipients.
Methods: We studied 96,109 kidney transplant recipients identified from the Scientific Registry of Transplant Recipients who received their transplant between January 1, 2010 and December 31, 2016 and were followed for mortality through June 30, 2019. Annual PM_2.5 concentration at the time of transplant was estimated at each recipient’s zip code using derived from National Aeronautics and Space Administration satellite data. Multilevel cox proportional hazards models were used to estimate hazard ratios (HR, 95% confidence intervals [CI]) for post-transplant mortality by zip code PM_2.5 concentration.
Results: 61% of recipients were male, 48% non-Hispanic (NH) White and the median age at transplant was 53 years. The median zip code PM_2.5 concentration was 9.1µg/m³. After a median of 4.0 years of follow-up, there were 14,260 deaths. After multivariable adjustment, recipients living in zip codes in the highest quartile of PM_2.5 exposure (≥10.7µg/m³) had 5% higher (HR: 1.05, 95% CI: 1.00, 1.10) risk for post-transplant mortality compared to recipients in zip codes in the lowest quartile of PM_2.5 exposure (<7.6µg/m³). These finding were stronger in recipients >65 years of age (HR: 1.09, 95% CI: 1.01, 1.18) and in NH White and NH Black recipients compared to recipients of other race/ethnicities.
Conclusions: Among US kidney transplant recipients, living in areas with higher exposure to PM_2.5 was associated with increased risk for mortality following transplantation. Additional management of kidney transplant recipients who might be exposed to moderate air pollution may help reduce mortality in this population.