Higher ambient nitrogen dioxide is associated with an elevated risk of hospital-acquired acute kidney injury

Background. Previous studies have suggested that long-term exposure to air pollution increases the risk of chronic kidney disease and its progression. However, the effect of air pollution on the risk of acute kidney injury (AKI) has not been studied. We aim to evaluate the transient effect of air pollution on the risk of hospital-acquired AKI (HA-AKI). Methods. We selected from the Epidemiology of AKI in Chinese Hospitalized patients cohort AKI cases in which the onset date could be unambiguously determined. We obtained city-specific daily averages of the ambient level of particulate matter (2.5 mu m and 10 mu m), carbon monoxide, nitrogen dioxide (NO2), sulfur dioxide (SO2) and ozone (O-3) from the Ministry of Environmental Protection of China. We used the time-stratified case-crossover approach to examine the association between the ambient level of air pollutants and the risk of HA-AKI in the selected cases. Results. A total of 11 293 AKI cases that met the inclusion and exclusion criteria were selected. In univariable analysis, the ambient levels of NO2 and SO2 were significantly associated with the risk of HA-AKI. In the multivariable analysis that incorporated all six pollutants in the same model, NO2 was the sole pollutant whose level remained associated with the risk of AKI (P < 0.001). The relationship between the level of NO2 and the risk of HA-AKI appeared to be linear, with an estimated odds ratio of 1.063 (95% confidence interval 1.026-1.101) for each increment of 1 median absolute deviation in the exposure. The association was consistent across the subgroups stratified by age, gender, baseline estimated glomerular filtration rate, AKI severity, need for intensive care and season. Conclusions. Higher ambient levels of NO2 are associated with an increased risk of HA-AKI in hospitalized adults in China.