Persistent racial and gender disparities in heart transplantation rates despite adjustment for sensitization and medical urgency in the modern allocation era

Background

Despite the 2018 revision of the United States heart allocation system, demographic disparities in transplantation persist. Historically, male sex and Black race have been associated with longer wait times, but the extent to which these disparities are driven by biological constraints versus structural inequities remains undefined.

Methods

We conducted a retrospective cohort study of 31,528 adult heart transplant candidates listed in the UNOS STAR registry between October 2018 and September 2025. Disparities were analyzed in three phases: (1) Unadjusted median wait times; (2) Demographically Adjusted Cox proportional hazards modeling (controlling for age, race, sex, blood type); and (3) Fully Adjusted modeling (controlling for clinical acuity, insurance, sensitization [cPRA], and Predicted Heart Mass [PHM]).

Results

Unadjusted analysis revealed significant delays for male and Black candidates, with Black males experiencing the longest median wait time (51.5 days) compared to the overall cohort (41.0 days).

In the Demographically Adjusted model, these disparities persisted: male sex was associated with a lower likelihood of transplantation (HR 0.83; 95% CI 0.78–0.89; P < 0.001), and Black race was associated with a disadvantage relative to White candidates (HR 0.93; 95% CI 0.87–0.98; P < 0.001).

However, in the Fully Adjusted model (which accounted for anthropometric measures, clinical acuity and cPRA) the gender disparity was completely reversed: male sex became an independent predictor of higher transplant likelihood (HR 1.12; 95% CI 1.06–1.18; P < 0.001). PHM was identified as the primary driver of this shift (HR 0.99 per unit increase), confirming that the "male disadvantage" is an artifact of size-matching constraints. Conversely, the racial disparity for Black candidates was not explained by clinical or anthropometric adjustment and worsened in the fully adjusted model (HR 0.88; 95% CI 0.85–0.91; P < 0.001).

Conclusions

The mechanisms driving demographic disparities in heart transplantation are distinct. The gender disparity observed in unadjusted and demographically adjusted analyses is a biological artifact of supply-demand mismatches for large donor hearts. in contrast, the racial disparity facing Black candidates is a persistent structural inequity that is not explained by biological, clinical, or anthropometric factors.For image description, please refer to the figure legend and surrounding text.For image description, please refer to the figure legend and surrounding text.