Assessment of neurocognitive functioning in sickle cell disease and thalassaemia and the association with silent cerebral infarcts, cerebral haemodynamics and oxygen metabolism.

Neurocognitive impairment is a key concern in sickle cell disease (SCD) patients, affecting several factors including academic performance, employment and quality of life. While the exact causes remain unclear, correlations with silent cerebral infarcts (SCIs) and abnormal perfusion and oxygenation have been reported in paediatric SCD populations. This study aimed to examine these associations in adults with SCD, including 70 severe SCD patients (HbSS & HbSβ⁰-thal), 22 mild SCD patients (HbSC & HbSβ⁺-thal), 16 thalassaemia patients and 29 healthy controls. We assessed seven neurocognitive domains: attention, working memory, processing speed, non-verbal IQ, verbal learning, visual memory and fine motor dexterity. Additionally, we analysed relationships between neurocognitive performance, SCIs, haemodynamics and oxygen metabolism parameters, including cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO₂). Our findings reveal that only processing speed was affected in SCD patients relative to norms, thalassaemia patients and controls. Fine motor dexterity was lower across all groups, possibly due to normative data not reflecting the transition from handwriting to typing. Notably, we found no correlation between neurocognitive performance, SCIs and perfusion and oxygenation parameters, suggesting that reduced processing speed may stem from other SCD-related factors, highlighting the need for further research.