Heterogeneous 30-day readmission risk in diabetic kidney disease: a nationwide analysis stratified by phenotype, age, and socioeconomic status.

<h4>Background</h4>Diabetic kidney disease (DKD) carries substantial hospital readmission burden. We characterized 30-day readmission patterns following DKD hospitalization, with stratified analyses by phenotype, age, and social determinants of health (SDOH).<h4>Methods</h4>Using the 2018 Nationwide Readmissions Database (NRD) with complex survey-weighted analysis, we identified adult index hospitalizations with a discharge diagnosis of DKD (ICD-10-CM E10.21, E10.22, E11.21, or E11.22) in any diagnostic position (January-November 2018). Survey-weighted multivariable logistic regression compared type 1 versus type 2 DKD, with separate models fitted within strata of age group, insurance type, and median household income quartile. Wald interaction tests assessed whether the phenotype association differed across strata.<h4>Results</h4>Among 1,291,033 index hospitalizations, the 30-day all-cause readmission rate was 15.96% (95% CI 15.78%-16.14%), higher for type 1 than type 2 DKD (22.42% vs. 15.69%; p<0.001). Non-diabetes-related systemic diagnoses accounted for 91.97% of readmissions. Type 1 DKD exhibited an inverse age-readmission gradient (28.8% in patients <40 years to 15.2% in those >79 years; age × phenotype interaction p = 9.28×10⁻¹⁴). The strongest independent predictors were ESRD (aOR 1.591), heart failure (aOR 1.348), and type 1 DKD (aOR 1.288; all p<0.001). Medicaid insurance was associated with higher readmission odds than Medicare (aOR 1.037; 95% CI 1.007-1.069; BH-adjusted p = 0.020). Median household income quartile was not independently associated with readmission.<h4>Conclusions</h4>Readmission risk in DKD is heterogeneous across diabetes phenotype, age, and socioeconomic strata, driven predominantly by non-diabetes-related systemic comorbidities. Insurance type modified the phenotype-readmission association, most markedly among Medicaid-insured patients.