Mind the gap: trajectory of cognitive development in young individuals with sickle cell disease: a cross-sectional study

STUDY OBJECTIVES

Compared to typically developing children and young adults (CYA-TD), those living with Sickle Cell Disease (CYA-SCD) experience more cognitive difficulties, particularly with executive function. Few studies have examined the relative importance of silent cerebral infarction (SCI), haemoglobin and arterial oxygen content on age-related cognitive changes using cross-sectional or longitudinal (developmental trajectory) data. This study presents cohort data from a single timepoint to inform studies with multiple timepoints.

METHODS

We compared cross-sectional raw and scaled scores as age-related changes in cognition (trajectories) in CYA-SCD and age-and ethnicity-matched CYA-TD. We also compared cross-sectional age-related changes in cognition (trajectories) in CYA-SCD with and without SCI to CYA-TD. General cognitive abilities were assessed using Wechsler Intelligence Scales, including the Verbal Comprehension Index (VCI) and Perceptual Reasoning Index (PRI) underpinning IQ. Executive function was evaluated using the Delis-Kaplan Executive Function System (D-KEFS) Tower subtest and the Behaviour Rating Inventory of Executive Function (BRIEF) questionnaire. SCI were identified from contemporaneous 3 T MRI; participants with overt stroke were excluded. Recent haemoglobin was available and oxygen saturation (SpO2) was measured on the day of the MRI.

RESULTS

Data were available for 120 CYA-SCD [62 male; age = 16.78 ± 4.79 years; 42 (35%) with SCI] and 53 CYA-TD (23 male; age = 17.36 ± 5.16). Compared with CYA-TD, CYA-SCD experienced a delayed onset in VCI and slower rate of development for BRIEF Global Executive Composite, Metacognition Index (MI), and Behaviour Regulation Index. The rate of executive function development for the BRIEF MI differed significantly between CYA-TD and CYA-SCD, with those with SCI showing a 26% delay compared with CYA-TD. For CYA-SCD with SCI, arterial oxygen content explained 22% of the variance in VCI and 37% in PRI, while haemoglobin explained 29% of the variance in PRI.

CONCLUSION

Age-related cognitive trajectories of CYA-SCD may not be impaired but may progress more slowly. Longitudinal studies are required, using tests unaffected by practice. In addition to initiation of medical treatment, including measures to improve arterial oxygen content, early cognitive intervention, educational support, and delivery of extracurricular activities could support cognitive development for CYA-SCD.Graphical Abstract.

Exploring the relationship of sleep, cognition, and cortisol in sickle cell disease

Background

Neurocognitive impairment is common in people with Sickle Cell Disease (SCD) and evidence is accumulating that sleep disturbances play a role. The interaction between cortisol and sleep in the general population is associated with cognition as well as general wellbeing but there are few data in SCD. We aimed to understand the relationship between cortisol and sleep in individuals with SCD and explored associations with cognition.

Methods

Forty-five participants of black heritage (SCD: N = 27, 9–29 years, 16 females; Controls: N = 18, 11–25 years, 13 females) were recruited from the community between 2018 - 2020. Participants completed standardized questionnaires about their sleep behaviour and wore actigraphy MotionWatch8 for 7 nights to assess nocturnal sleep patterns. Salivary cortisol samples were taken on wakening and 3 times after 14:00. Cognition was assessed using the Wechsler Intelligence Scales for children and adults.

Results

People with SCD took longer to fall asleep and experienced greater wake bouts, mobile minutes and fragmented sleep compared to controls. Although non-significant, people with SCD experienced lower morning cortisol, with a flattened diurnal cortisol ratio compared to controls. Interestingly, SCD participants, but not controls, with low diurnal variation scored lowest on processing speed (PSI) and perceptual reasoning index (PRI). A moderator analysis revealed that the effect of morning cortisol and diurnal cortisol ratio on PRI by group health (i.e., SCD and healthy controls) depended on sleep quality.

Discussion

Sleep and cortisol may play a crucial role in the expression of cognitive difficulties seen in SCD. This should be considered for the development of interventions to optimise cognitive functioning and sleep. This, in turn, could positively impact on secretion of cortisol and general health in SCD.

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We examined sleep patterns, cortisol and cognition in 27 participants with Sickle Cell Disease (SCD) and 18 healthy controls.

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People with SCD had lower cognitive scores compared to healthy controls.

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People with SCD took longer to fall asleep, had greater wake bouts, mobile minutes, and fragmented sleep.

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People with SCD experienced a flattened diurnal cortisol profile.

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Sleep disturbances might interfere with diurnal cortisol rhythm and contribute to lower cognitive scores .

The Raven's Coloured Progressive Matrices in Healthy Children: A Qualitative Approach

Studies on the structure of intelligence refer to two main theoretical models: the first one considers intelligence as a unitary construct, the second one assumes the involvement of a plurality of factors. Studies using Raven's Coloured Progressive Matrices (RCPM) tasks have often highlighted the involvement of different cognitive abilities and brain structures, but in the clinical setting, RCPM measurement continues to be used as a single score. The current study aimed to analyse the RCPM performance following qualitative clustering, in order to provide an interpretation of the intelligence assessment through a factorial criterion. The RCPM have been administered to a large group of typically developing children between 6 and 11 years of age. The sample was divided into twelve age groups, and the performance of each age group was shown. Three qualitative item clusters were identified through a factorial criterion. Data showed that performance on RCPM may arise from different cognitive abilities, starting from basic attentional skills up to the more complex ones that require perceptual or analogical reasoning. The qualitative parameters could provide more effective diagnostic and treatment suggestions than a single total score in the clinical setting, and may be crucial for focusing on strength and weakness in the intellectual functionality evaluation of children.

Frequency of occurrence of four- and five-factor WAIS-IV profiles

Interpretive strategies for the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) include Wechsler's four-factor structure and the five-factor Cattell-Horn-Carroll (CHC) model. The frequency of profile occurrence and the contribution of demographic- and ability-related variables to their incidence are unknown. Current participants were 291 referrals (males = 134; female = 157) for neuropsychological evaluation with mean years for age and education of 34.94 (SD = 13.53) and 12.74 (SD = 2.46), respectively. Lichtenberger and Kaufman's guidelines for selecting each model were applied. Of the total, 67.3% were four-factor and 32.6% were five-factor profiles. The same pattern emerged when participants were subdivided by gender, education, ethnicity, IQ, and diagnosis. A noteworthy association between IQ and profile type emerged. When IQ increased, four-factor profiles declined and five-factors increased. A logistic regression, using demographics, IQ, and diagnosis as predictors, correctly classified 64.8% of participants. The average subtest intercorrelations and g saturations in the four-factor group were substantially larger than those for five-factor participants. These findings were consistent with Spearman's differentiation by ability hypothesis.

Use of translated and adapted versions of the WISC-V: Caveat emptor

The Wechsler Intelligence Scale for Children (WISC) is the most widely used intelligence test in the world. Now in its fifth edition, the WISC-V has been translated and adapted for use in nearly a dozen countries. Despite its popularity, numerous concerns have been raised about some of the procedures used to develop and validate translated and adapted versions of the test around the world. The purpose of this article is to survey the most salient of those methodological and statistical limitations. In particular, empirical data are presented that call into question the equating procedures used to validate the WISC-V Spanish, suggesting cautious use of that instrument. It is believed that the issues raised in the present article will be instructive for school psychologists engaged in the clinical assessment of intelligence with the WISC-V Spanish and with other translated and adapted versions around the world.

Measurement Invariance Across Gender on the Second-Order Five-Factor Model of the German Wechsler Intelligence Scale for Children-Fifth Edition

The present study investigated measurement invariance across gender on the German Wechsler Intelligence Scale for Children-Fifth Edition (WISC-V). The higher order model that was preferred by the test publishers was tested on a population-representative German sample of 1,411 children and adolescents aged between 6 and 16 years. Confirmatory factor analyses were conducted to test for measurement invariance. As soon as partial scalar invariance could be established by freeing nonequivalent subtest intercepts, results demonstrated that 11 out of 15 subtest scores have the same meaning for male and female children. These findings support interpretable comparisons of the WISC-V test scores between males and females but only in due consideration of partial scalar invariance and with respect to the underlying factor structure. Despite this, however, results did not support the overall structural validity of the higher order model. Thus, replacing the former Perceptual Reasoning factor by Fluid Reasoning and Visual Spatial may be considered inappropriate due to the redundancy of the FRI as a separate factor. Results also indicated that the WISC-V provides stronger measurement of general intelligence (Full Scale IQ) than measurements of cognitive subdomains (WISC-V indexes). Interpretative emphasis should thus be placed on the Full Scale IQ rather than the WISC-V indexes.

Construct Validity of the WISC-V in Clinical Cases: Exploratory and Confirmatory Factor Analyses of the 10 Primary Subtests

Independent exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) research with the Wechsler Intelligence Scale for Children-Fifth Edition (WISC-V) standardization sample has failed to provide support for the five group factors proposed by the publisher, but there have been no independent examinations of the WISC-V structure among clinical samples. The present study examined the latent structure of the 10 WISC-V primary subtests with a large (N = 2,512), bifurcated clinical sample (EFA, n = 1,256; CFA, n = 1,256). EFA did not support five factors as there were no salient subtest factor pattern coefficients on the fifth extracted factor. EFA indicated a four-factor model resembling the WISC-IV with a dominant general factor. A bifactor model with four group factors was supported by CFA as suggested by EFA. Variance estimates from both EFA and CFA found that the general intelligence factor dominated subtest variance and omega-hierarchical coefficients supported interpretation of the general intelligence factor. In both EFA and CFA, group factors explained small portions of common variance and produced low omega-hierarchical subscale coefficients, indicating that the group factors were of poor interpretive value.

Hierarchical Structure of the Wechsler Adult Intelligence Scale–Fourth Edition with an Egyptian Sample

The Wechsler Adult Intelligence Scale–Fourth Edition (WAIS-IV) is one of the most well-known tests in the field of adult intelligence assessment. This study explores the validity of the Egyptian adaptation for the subscales of the WAIS-IV. Confirmatory factor analysis (CFA) indicated that the first-order, second-order, and bifactor models of both the five-factor Cattel–Horn–Carroll (CHC) and the four-factor structures fitted with the WAIS-IV. When the Arithmetic subscale was pathed to Perceptual Reasoning and Working Memory, the modified four first-order factor showed a better fit than any other model. Estimates of internal consistency revealed that Cronbach’s alpha was very high (.91) for the WAIS-IV scale and for four-factor structures (ranging from .81 to .95), while [Formula: see text] was low (0.61) for the WAIS-IV scale and for four-factor structures, ranging from 0.20 to 0.68. Overall, these findings provided adding evidence about the dimensionality of WAIS-IV with a new sample.

Predictive Value of Traditional Measures of Executive Function on Broad Abilities of the Cattell–Horn–Carroll Theory of Cognitive Abilities

The neuropsychological construct of executive functions (EFs), and the psychometric Cattell–Horn–Carroll (CHC) theory of cognitive abilities are both approaches that attempt to describe cognitive functioning. The coherence between EF and CHC abilities has been mainly studied using factor-analytical techniques. Through multivariate regression analysis, the current study now assesses the integration of these latent constructs in clinical assessment. The predictive power of six widely used executive tasks on five CHC measures (crystallized and fluid intelligence, visual processing, short-term memory, and processing speed) is examined. Results indicate that executive tasks—except for the Stroop and the Tower of London—predict overall performance on the intelligence tests. Differentiation in predicting performance between the CHC abilities is limited, due to a high shared variance between these abilities. It is concluded that executive processes such as planning and inhibition have a unique variance that is not well-represented in intelligence tests. Implications for the use of EF tests and operationalization of CHC measures in clinical practice are discussed.

What Does the WRAML2 Core Battery Measure? Utilizing Exploratory and Confirmatory Techniques to Disclose Higher Order Structure

The present study examined the factor structure of the Wide Range Assessment of Memory and Learning-Second Edition (WRAML2) core battery with participants from the normative sample aged 9 to 90 years ( n = 880) using higher order exploratory and confirmatory factor analytic techniques that were not reported in the in the WRAML2 Administration and Technical Manual. Exploratory factor analysis results suggested only one factor, whereas confirmatory factor analysis results favored the three factors posited by the test authors. Although model fit statistics were equivalent for the oblique, indirect hierarchical, and direct hierarchical measurement models, it was determined that the bifactor model best disclosed the influence of latent dimensions on WRAML2 manifest variables. In the three-factor bifactor model, the general factor accounted for 31% of the total variance and 69% of the common variance, whereas the three first-order factors combined accounted for 41% of the total variance and 31% of the common variance. Latent factor reliability coefficients (as estimated by ω_h) indicated that only the general factor was measured with enough precision to warrant confident clinical interpretation. Implications for clinical interpretation of WRAML2 scores and the procedures utilized in the development of related measures are discussed.

Patterns of Cognitive Strengths and Weaknesses and Relationships to Math Errors

This study investigated cognitive patterns of strengths and weaknesses (PSW) and their relationship to patterns of math errors on the Kaufman Test of Educational Achievement (KTEA-3). Participants, ages 5 to 18, were selected from the KTEA-3 standardization sample if they met one of two PSW profiles: high crystallized ability (Gc) paired with low processing speed/long-term retrieval (Gs/Glr; n = 375) or high Gs/Glr paired with low Gc ( n = 309). Estimates of Gc and Gs/Glr were based on five KTEA-3 subtests that measure either Gc (e.g., Listening Comprehension) or Gs/Glr (e.g., Object Naming Facility). The two groups were then compared on math error factors. Significant differences favored the High-Gc group for factors that measure math calculation, basic math concepts, and complex computation. However, the two groups did not differ in their errors on factors that measure geometry/measurement or simple addition. Results indicated that students with different PSW profiles also differed in the kinds of errors they made on math tests.

Structural Validity of the WISC-IV for Students With Learning Disabilities

The structural validity of the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) was evaluated using confirmatory factor analysis for a clinical sample of 1,537 students diagnosed with specific learning disabilities (SLD) by school psychologists in two large southwestern school districts. Results indicated that a bifactor model consisting of four first-order domain specific factors and a general intelligence breadth factor fit the data best. Consequently, the structural validity of the WISC-IV for students with SLD was supported by the results of the present study. The general intelligence factor contributed the most information, accounting for 48% of the common variance. Given this structure, it was recommended that score interpretation should emphasize the Full-Scale IQ score because of the marginal contributions of the first-order domain-specific factors and their low precision of measurement independent of the general factor.

Representation of the Cattell–Horn–Carroll Theory of Cognitive Abilities in the Factor Structure of the Dutch-Language Version of the WAIS-IV

The Cattell–Horn–Carroll (CHC) theory of cognitive abilities has been guiding in the revision of the Wechsler Adult Intelligence Scale–Fourth edition (WAIS-IV). Especially the measurement of fluid reasoning (Gf) is improved. A total of five CHC abilities are included in the WAIS-IV subtests. Using confirmatory factor analysis, a five-factor model based on these CHC abilities is evaluated and compared with the four index scores in the Dutch-language version of the WAIS-IV. Both models demonstrate moderate fit, preference is given to the five-factor CHC model both on statistical and theoretical grounds. Evaluation of the WAIS-IV according to CHC terminology enhances uniformity, and can be important when interpreting possible sources of index discrepancies. To optimally assemblage CHC and WAIS-IV, more knowledge of the interaction of abilities is needed. This can be done by incorporating intelligence testing in neuropsychological assessment. Using this functional approach contributes to a better understanding of an individual’s cognitive profile.

Implications for Educational Classification and Psychological Diagnoses Using the Wechsler Adult Intelligence Scale–Fourth Edition With Canadian Versus American Norms

Building on a recent work of Harrison, Armstrong, Harrison, Iverson and Lange which suggested that Wechsler Adult Intelligence Scale–Fourth Edition (WAIS-IV) scores might systematically overestimate the severity of intellectual impairments if Canadian norms are used, the present study examined differences between Canadian and American derived WAIS-IV scores from 861 postsecondary students attending school across the province of Ontario, Canada. This broader data set confirmed a trend whereby individuals’ raw scores systematically produced lower standardized scores through the use of Canadian as opposed to American norms. The differences do not appear to be due to cultural, educational, or population differences, as participants acted as their own controls. The ramifications of utilizing the different norms were examined with regard to psychoeducational assessments and educational placement decisions particularly with respect to the diagnoses of Learning Disability and Intellectual Disability.

What Does the Shipley-2 Measure for Children and Adolescents? Integrated and Conjoint Confirmatory Factor Analysis With the WISC-IV

We used integrated and conjoint confirmatory factor analysis of Shipley-2 and Wechsler Intelligence Scale for Children–Fourth Edition (WISC-IV) data to investigate constructs measured in the Shipley-2 for children and adolescents. We also estimated Shipley-2 composite reliability at the subtest level rather than the item level. The three Shipley-2 subtests for the most part measured what was described in the manual, although Block Patterns measured visual spatial ability in addition to fluid ability and Abstraction was best considered a measure of psychometric g. The g factors derived from the WISC-IV and Shipley-2 were similar but not identical. Internal reliability estimates for Shipley-2 composites that were based on correlations between the subtests were substantially lower than those based on the items. Last, based on WISC-IV derived g factors, 37% to 53% of the variance in Shipley-2 composites was explained by g. Some of the reliable variance in the Shipley-2 composites was due to something specific that the subtests had in common not explained by psychometric g.

Intelligent Testing With Wechsler’s Fourth Editions

The two featured articles and eight commentaries on the WISC-IV (Wechsler, 2003) and WAIS-IV (Wechsler, 2008) in this special issue of Journal of Psychoeducational Assessment are of exceptional quality. As a collective, this special issue greatly advances the field of cognitive assessment by intelligently synthesizing the best of methodology (confirmatory factor analysis) with the best of theory (Cattell–Horn–Carroll). The Weiss et al. articles represent sophisticated approaches to test validation and interpretation and the commentaries deal with applications, extensions, and limitations of the findings. This “response to the respondents” focuses on Wechsler’s approach to assessment, historical antecedents of factor analysis (especially the contributions of Jacob Cohen in the 1950s), and the “intelligent testing” model of test interpretation.

An Introduction to the Wechsler Intelligence Tests

This special issue focuses on two lead articles examining the factor structure of the fourth editions of the Wechsler Adult Intelligence Scales (WAIS-IV; Wechsler, 2003) and the Wechsler Intelligence Scales for Children (WISC-IV; Wechsler, 2008). These articles are followed by 9 commentaries and a final response by the authors of the lead articles. These diverse approaches critically assess the theoretical and practice implications of the structure of intelligence measured by the Wechsler scales.

Technical and Practical Issues in the Structure and Clinical Invariance of the Wechsler Scales

This discussion article addresses issues related to expansion of the Wechsler model from four to five factors; multiple broad CHC abilities measured by the Arithmetic subtest; advantages and disadvantages of including complex tasks requiring integration of multiple broad abilities when measuring intelligence; limitations of factor analysis, which constrain test developers to creating specific broad and narrow abilities as opposed to integrative tasks; implications from brain imaging research showing the critical role of neurological pathways that integrate brain regions; close relationship of the fluid reasoning factor to g, and the inadequacies of factor analytically driven statistical definitions of g in the development of improved models of intelligence. In this rejoinder to the commentaries in this special issue on structural models of the WAIS-IV and WISC-IV, the advantages and disadvantages of Schmid–Leiman’s transformation, which removes the effects of g on the broad abilities, and the use of nested or bifactor models in evaluating models of intelligence are also discussed.