Abstract
<title>Abstract</title> <p> <bold>Introduction:</bold> Acute kidney injury (AKI) and chronic kidney disease (CKD) are common and interrelated conditions associated with substantial morbidity and mortality. Although Black patients experience higher rates of both AKI and CKD, prior studies have paradoxically reported improved survival among Black patients with AKI. The interaction between race, sex, AKI, and CKD at a national level remains incompletely understood. We evaluated temporal trends and outcomes among hospitalized patients with AKI, with particular focus on racial and sex differences in patients with AKI superimposed on CKD. <bold>Methods:</bold> We performed a retrospective analysis of the National Inpatient Sample from 2016–2022. Adult hospitalizations with AKI were identified using ICD-10 codes and stratified by the presence or absence of CKD. Demographic characteristics, in-hospital mortality, and new dialysis initiation were analyzed. Multivariable logistic regression adjusted for age, sex, race, insurance status, Elixhauser comorbidity score, and geographic region was used. <bold>Results:</bold> Among 241,001,880 hospitalizations, 33,213,067 patients (13.8%) developed AKI, including 12,904,310 (38.9%) with CKD. The proportion of admissions complicated by AKI increased from 11.1% in 2016 to 15.8% in 2022, while AKI occurring in patients with CKD increased from 3.3% to 7.3% of all hospitalizations. Black patients were more likely to have CKD among those with AKI (20.2% vs. 17.3%; adjusted OR 1.40, p < 0.001). Overall mortality was lower in patients with AKI/CKD than in those with AKI alone (6.6% vs. 9.2%). Within the AKI/CKD cohort, Black patients had lower unadjusted mortality than non-Black patients (5.4% vs. 7.6%), but after adjustment Black race was associated with a modest increase in mortality risk (OR 1.04). New dialysis was more common in AKI/CKD than AKI alone (7.8% vs. 4.7%) and remained significantly associated with Black race after adjustment (OR 1.34). Female sex was associated with lower mortality and lower dialysis. <bold>Conclusions:</bold> Hospitalizations complicated by AKI, particularly AKI superimposed on CKD, increased substantially between 2016 and 2022. Black patients were more likely to have CKD and require dialysis, while female sex was associated with lower mortality and dialysis utilization. These findings highlight the growing burden of AKI on CKD and underscore persistent racial and sex-based disparities that warrant further investigation and targeted intervention. <bold>Clinical trial registration</bold> N/A </p>