Processing Speed May Be Slower in People Who Have SCD

Cerebral blood flow (CBF) could be higher and processing speed slower in patients with sickle cell disease (SCD). This finding, published in Journal of Neurology and Experimental Neural Science, could validate findings that processing speed is correlated with the degree of elevated CBF, which is correlated to the degree of anemia in patients.

SCD is estimated to affect 70,000 to 100,000 individuals in the United States, with cognitive deficiencies found to be associated with SCD and manifesting in poorer academic achievement and general intellectual abilities. However, the specifics of these deficits are not fully researched. CBF is indirectly the result of a reduction in brain oxygen delivery and is the strongest predictor of stroke in children with SCD. This study aimed to represent “an initial pilot study to investigate correlational patterns that may have implications for larger investigations into CBF and cognitive performance among patients with SCD.”

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An urban academic medical center in central Virginia was used to recruit participants with SCD who were aged 22 to 52 years and were of African American descent. All participants underwent an MRI scan. The NIH Toolbox Dimensional Change Card Sort Test (DCCS) was used to assess cognitive flexibility, and the NIH Toolbox Flanker Inhibitory Control and Attention Test was used to evaluate executive function. Processing speed was also assessed in all participants through an indirect functional marker of ischemia, the Pattern Comparison Processing Speed Test.

There were 7 participants with SCD included in this study. T-test results found that adults with SCD had significantly higher CBF compared with healthy controls (mean [SD], 72.15 [28.9] vs 47.23 [12.30] mL/min/100 g; P = .04). Patients with SCD had lower cognitive flexibility (97.57 [5.43] vs 115.33 [8.29]; P = .29) and lower executive function (79.71 [7.10] vs 119.33 [10.71]; P = .12) compared with controls, but this finding was not significant.

Participants with SCD were also found to have significantly lower processing speed compared with the healthy controls (96.14 [7.36] vs 123.00 [11.25]; P = .02). Processing speed was found to be associated with CBF, as higher CBF corresponded to decreasing processing speed. Analysis of variance tests found that the differences in CBF and processing speed in each genotype of SCD were not statistically significant. Adults with SCD generally took longer to complete the cognitive assessment.

There were some limitations to this study. There was a small sample size, which necessitates larger studies to corroborate the results; direct comparisons with validated neuropsychological measures are needed to truly evaluate processing speed testing. Also, the primary contributor to observed cognitive impairment could not be determined between cognitive processing or motor speed using the NIH Toolbox tests.

The researchers concluded that diagnosing cognitive difficulties in adults with SCD at an earlier time could be beneficial to treating these patients. Objective measurements of baseline cognitive function, analysis of brain flood flow, and the associations between the measures should be evaluated to determine cognitive difficulties to improve clinical care and quality of life.

Reference

Sop D, Steinberg JL, Jordan J, Crouch T, Zhang YM, Smith W. Association of cerebral hemodynamics and anemia on processing speed in adults with sickle cell disease. J Neurol Exp Neural Sci. 2023;5(1):150. doi:10.29011/2577-1442.100050