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Processing Speed Decline Over Time Identified in Individuals With Sickle Cell Disease


A retrospective study reveals that measures of cognitive function, specifically processing speeds, decline in individuals with sickle cell disease as they grow older.

Sickle cell disease (SCD) can cause developmental delays in children, such as delays in processing speeds, that worsen with age and disease progression, according to a recent study published in Children.

In SCD, sickled red blood cells are unable to transport oxygen as well as healthy red blood cells. This decreased capacity alongside the occlusion of blood vessels and the disease’s overall vascular pathology leave affected individuals more vulnerable to brain injury. Additionally, patients with SCD can experience neurocognitive complications that can lead to cognitive deficiencies and stroke.

Cognitive Decline Written on Chalk Board | image credit: Andrii - stock.adobe.com

Cognitive Decline Written on Chalk Board | image credit: Andrii - stock.adobe.com

Young people with SCD may be affected by cognitive deficiencies such as poor attention, memory, and processing, as well as executive dysfunction. These complications can impact individual coping skills, school success, and their overall quality of life.

The Processing Speed Index (PSI) is a standardized score that is included in an individual’s Full Scale IQ assessment. As the authors of the present study indicate, more evidence has begun suggesting that younger individuals with SCD are exhibiting lower PSI scores that either decline or remain stable when compared with control groups. However, the authors add that most studies on SCD and cognition have been concerned with executive functions and actual intelligence (IQ). Very little research has been dedicated to investigating long-term changes in processing speed experienced by young people enduring SCD. Because processing speed deficiencies can influence other cognitive difficulties, the authors continued, a study was conducted to discern whether processing speeds in children and young people with SCD decline over time.

Data were retrospectively evaluated from MRI, Full Scale Intelligence Quotient (FSIQ), and PSI scores from the East London Sickle Cell Disease Cohort, a longitudinal dataset spanning from 1992 until 2001. A total of 105 patients with SCD who were recruited during routine hemoglobinopathy clinic appointments were included. Analyses and follow-up were conducted at 3 different timepoints (1: 1992-2001; 2: 1997-2001; 3: 2001-2002).

Participants were aged 3 to 16 years at timepoint 1 (n = 103), 9 to 16 years at timepoint 2, and 10 to 25 years at timepoint 3. Older and younger children both trended toward the lower-average range for PSI scores. Younger children had statistically significantly higher IQ compared with older children (P < .03). Additionally, declines were most prevalent in the coding subtest for processing speed. This depreciation had a significant interaction with age and timepoint (P = .01). The authors saw these results as possible reflections of developmental delays associated with disease progression, which they mentioned could be influenced by the prominence of stroke or silent cerebral infarctions in their cohort.

Of the limitations the authors encountered in their study, they primarily noted the unavailability of disease-modifying treatments at the start of their recruitment. For this reason, they were unable to take into account a patient’s treatment status in their assessment. Nonetheless, the authors still stress the important implications of their findings for implementing clinical monitoring strategies and develop earlier interventions in this patient population.


Walker EJ, Kirkham FJ, Hood AM. Decline in processing speed tells only half the story: developmental delay in children living with sickle cell disease. Children. 2024;11(3):277. doi:10.3390/children11030277

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