Cognitive Performance in Transfusion-Dependent Adults with β-Thalassemia in Bulgaria: A Case-Control Study

Background: As survival improves in transfusion-dependent β-thalassemia, long-term adult morbidity, including cognitive dysfunction, has become increasingly relevant. Adult data remain limited, particularly in Eastern Europe, and many studies rely on single screening tools with limited control for confounding. Methods: We conducted a single-center case-control study (2024-2025) at the Congenital Hemolytic Anemia Treatment Center, University Hospital "Sv. Georgi" Plovdiv, Bulgaria. Fifty adults with transfusion-dependent β-thalassemia (86% thalassemia major; 14% transfusion-dependent intermedia) and 30 frequency-matched healthy controls completed a multi-domain cognitive battery: Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE), Clock Drawing Test (CDT), Trail Making Test (TMT-A/B), and timed verbal fluency. Associations between thalassemia status and cognitive outcomes were estimated using three prespecified models: unadjusted, adjusted for age and sex, and a doubly robust model combining covariate balancing propensity score inverse probability weighting (balancing BMI, smoking, education, and comorbidity) with age/sex regression adjustment. Results: Patients performed worse than controls on global cognition and executive/visuospatial measures. MoCA scores were lower in patients (-2.26 unadjusted, p = 0.016; -2.83 doubly robust, p = 0.001), as were MMSE scores (-1.64, p = 0.015; -1.87, p = 0.002). CDT performance was consistently poorer (OR ≈ 0.28-0.30 across models). Patients were slower on TMT-B (time ratio 1.35 unadjusted, p = 0.003; 1.42 doubly robust, p < 0.001); TMT-A reached significance only after weighting (ratio 1.32, p = 0.001). Verbal fluency was modestly lower with borderline significance (p ≈ 0.05-0.06). Conclusions: Transfusion-dependent β-thalassemia in adults is associated with poorer cognitive performance, particularly in global cognition and executive/visuospatial domains, with results robust across adjustment strategies. Routine multi-domain cognitive screening may be warranted in adult thalassemia care.