Adults with sickle cell disease may perform cognitive tests as well as controls when processing speed is taken into account: a preliminary case-control study

Aims. This study aimed to: (1) evaluate cognitive function among adults with sickle cell disease using a computer-administered neuropsychological test; and (2) replicate previously identified differences in processing speed between patients with sickle cell disease and controls. Background. Previous evidence suggests that, compared with controls, adult patients with sickle cell disease have poorer cognitive functioning across most domains but the most significant deficits appear to be in the area of processing speed. Design. Cross-sectional case-control study conducted from June 2008-June 2010. Methods. Cognitive functioning was measured using computerized, self-administered, neuropsychological tests among 31 patients with sickle cell disease and 17 controls matched for age, gender and race. The assessment averaged 30 minutes and scores were recorded for seven computerized tests: verbal and visual memory, finger tapping, symbol digit coding, Stroop test, shifting attention and continuous performance. Results. Patients with sickle cell disease scored 10.76 points lower on the CNS Vital Signs processing speed domain than controls. Although non-significant, patients scored 5.73 points lower on the full index than controls but after adjusting for processing speed, mean scores for patients were 3 points greater compared with controls. Differences in executive functioning and attention were not significant and memory did not differ between groups. Conclusion. Using a brief, computer-administered 30-minute neuropsychological test, we were able to replicate previous findings showing a greater than 10-point deficit in processing speed among patients with sickle cell disease. When differences in processing speed are taken into account, patients perform equally well or better than controls on cognitive tasks.