Mineral elements and adiposity-related consequences in adolescents with intellectual disabilities

BACKGROUND

Patients with intellectual disabilities are shown to have a limited capacity for cooperation, communication,and other biological consequences, which significantly require a specialized interest in healthcare professionals worldwide.

AIM

In this respect, the present study was designed to evaluate the levels mineral elements, and their correlation with oxidative stress markers and adiposity markers; leptin (L), adiponectin (A), and L/A ratio in adolescents with intellectual disabilities.

METHODS

A total of 350 schoolchildren aged (12-18 years) were randomly invited to participate in this prospective, observational study. Only 300 participants agreed to participate in this study. According to Intelligence quotients scores (IQ) measured by WISC-III, the participants were classified into two groups; the healthy control group (no = 180; IQ = 90-114); and the moderate intellectual disability (MID) group (no = 120; IQ = 35-49). Adiposity markers; body mass index (BMI), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), physical activity scores, adipokines biomarkers; leptin, adiponectin, L/A ratio, oxidative stress, and plasma mineral elements were evaluated by prevalidated questionnaires, inductively coupled plasma-mass spectrometry (ICP-MS), colorimetric, and immunoassay techniques.

RESULTS

Intellectual disability of moderate type was reported in 40% of the studied populations most of them are men aged 12-18 years (66.6% for men vs. 33.3 for females). Obesity was shown to be associated with the degree of intellectual disability of the students. There was a significant (P = 0.001) increase in the BMI, WHR, and WHtR scores as obesity markers with poor physical activity (P = 0.01) in students with poor disability compared to healthy controls (HC). The levels of leptin (P = 0.001), adiponectin (P = 0.01), and L/A ratio (P = 0.01) as adiposity biomarkers were significantly increased in students with MID compared to healthy controls. Also, oxidative stress measured by malondialdehyde (MDA) (P = 0.01) and total antioxidant capacity (TAC) (P = 0.01) were significantly increased in students with MID compared to healthy control subjects. In addition, mineral elements were shown to be linked with intellectual disability. The data showed that the levels of Fe, Mn, Zn, Hg, Pb, Ca, Cr, Mg, and Ni significantly (P = 0.001) increased, and the levels of Al, Na, K, Cu, and Zn/Cu ratio significantly (P = 0.001) decreased in subjects with MID compared to healthy controls. Correlation analysis concluded that changes in mineral elements significantly correlated with adiposity markers, oxidative stress, and the scores of intellectual disability (WISC III-IQ score).

CONCLUSION

The intellectual disability of moderate type (MID) was associated with abnormal changes in the levels of essential mineral elements and adipokines and increased levels of cellular oxidative stress. Thus, evaluating plasma mineral elements and adipokines levels could be a potential diagnostic parameter for diagnosing MID.

Dimensional Evaluation of Cognitive Measures: Methodological Confounds and Theoretical Concerns

The current study provides a methodological review of studies supporting a general factor of intelligence as the primary model for contemporary measures of cognitive abilities. A further evaluation is provided by an empirical evaluation that compares statistical estimates using different approaches in a large sample of children (ages 9–13 years, N = 780) administered a comprehensive battery of cognitive measures. Results from this study demonstrate the ramifications of using the bifactor and Schmid–Leiman (BF/SL) technique and suggest that using BF/SL methods limit interpretation of cognitive abilities to only a general factor. The inadvertent use of BF/SL methods is demonstrated to impact both model dimensionality and variance estimates for specific measures. As demonstrated in this study, conclusions from both exploratory and confirmatory studies using BF/SL methods are significantly questioned, especially for studies with a questionable theoretical basis. Guidelines for the interpretation of cognitive test scores in applied practice are discussed.

Physical activity impact on motor development and oxidative stress biomarkers in school children with intellectual disability

OBJECTIVE Lower physical fitness and poor motor performance were shown to be linked with higher levels of oxidative stress in children and adolescents with intellectual disabilities. Therefore, a moderate aerobic exercise for 12-weeks was performed to evaluate the effects of physical activity scores on motor functions, oxidative stress, and intelligence quotients (IQ) in school children with intellectual disability. METHODS A total of 65 school children aged (12-18 Yrs) were randomly included in this study. Intellectual disability (ID),motor skills,physical fitness(VO2max), total energy expenditure (TEE), MDA, 8-OHdG, TAC, NO, and total oxidative stress(OS)were assessed using pre-validated WISC-IQ score test, BOT-2 test, PA questionnaire, and immunoassay techniques respectively. RESULTS WISC-IQ and BOT-2 set scores of intellectual and motor skills performance showed a significant correlation with physical activity status and the regulation of oxidative stress-free radicals in school children with mild and moderate ID following 12 weeks of moderate exercise. The intellectual and motor skills performance of the participants correlated positively with the increase in TAC activity and physical fitness scores and negatively with MDA, 8-OHdG, NO, and Total-OS, respectively. Stepwise multiple regression analysis of the demographic, physical status and oxidative stress parameters explained around78.0 to 93.4 % of intellectual disability variation among schoolchildren. CONCLUSION Moderate aerobic training for12 weeks has a positive impact on improving intellectual ability of schoolchildren with ID via modulating redox status, improves physical fitness, and motor skills proficiency.

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.

Exploratory Factor Analyses of the Intelligence and Development Scales-2: Implications for Theory and Practice

The factor structure of the intelligence and scholastic skills domains of the Intelligence and Development Scales-2 was examined using exploratory factor analyses with the standardization and validation sample (N = 2,030, aged 5 to 20 years). Results partly supported the seven proposed intelligence group factors. However, the theoretical factors Visual Processing and Abstract Reasoning as well as Verbal Reasoning and Long-Term Memory collapsed, resulting in a five-factor structure for intelligence. Adding the three scholastic skills subtests resulted in an additional factor Reading/Writing and in Logical-Mathematical Reasoning showing a loading on abstract Visual Reasoning and the highest general factor loading. A data-driven separation of intelligence and scholastic skills is not evident. Omega reliability estimates based on Schmid-Leiman transformations revealed a strong general factor that accounted for most of the true score variance both overall and at the group factor level. The possible usefulness of factor scores is discussed.

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.

Modeling General, Specific, and Method Variance in Personality Measures: Results for ZKA-PQ and NEO-PI-R

Contemporary models of personality assume a hierarchical structure in which broader traits contain narrower traits. Individual differences in response styles also constitute a source of score variance. In this study, the bifactor model is applied to separate these sources of variance for personality subscores. The procedure is illustrated using data for two personality inventories-NEO Personality Inventory-Revised and Zuckerman-Kuhlman-Aluja Personality Questionnaire. The inclusion of the acquiescence method factor generally improved the fit to acceptable levels for the Zuckerman-Kuhlman-Aluja Personality Questionnaire, but not for the NEO Personality Inventory-Revised. This effect was higher in subscales where the number of direct and reverse items is not balanced. Loadings on the specific factors were usually smaller than the loadings on the general factor. In some cases, part of the variance was due to domains being different from the main one. This information is of particular interest to researchers as they can identify which subscale scores have more potential to increase predictive validity.

Age Differences and Educational Attainment Across the Life Span on Three Generations of Wechsler Adult Scales

Patterns of maintenance of ability across the life span have been documented on tests of knowledge ( Gc), as have patterns of steady decline on measures of reasoning ( Gf/Gv), working memory ( Gsm), and speed ( Gs). Whether these patterns occur at the same rate for adults from different educational backgrounds has been debated. In addition, age-related research is needed to study global IQs, especially in view of the increased reliance on IQ in capital punishment court cases. In this study, large representative samples of adults tested during the standardizations of three versions of the Wechsler Adult Intelligence Scale (WAIS) served as subjects: WAIS-R ( N = 1,480, ages 20-74), WAIS-III ( N = 2,093, ages 20-90), and WAIS-IV ( N = 1,800, ages 20-90). Based on regression analysis, patterns of aging on Full Scale IQ (FSIQ) and the four abilities (a) were essentially the same for males versus females and (b) characterized all levels of education across three generations of Wechsler’s adult scales.

Incremental validity of WISC-IV(UK) factor index scores with a referred Irish sample: predicting performance on the WIAT-II(UK.)

BACKGROUND

Subtest and factor scores have typically provided little incremental predictive validity beyond the omnibus IQ score.

AIMS

This study examined the incremental validity of Wechsler Intelligence Scale for Children - Fourth UK Edition (WISC-IV(UK) ; Wechsler, 2004a, Wechsler Intelligence Scale for Children - Fourth UK Edition, Harcourt Assessment, London, UK) and factor index scores in predicting academic achievement on the Wechsler Individual Achievement Test - Second UK Edition (WIAT-II(UK) ; Wechsler, 2005a, Wechsler Individual Achievement Test-Second UK Edition, Pearson, London, UK), beyond that predicted by the WISC-IV(UK) FSIQ.

SAMPLE

The sample included 1,014 Irish children (ages 6-0 to 16-9) who were referred for evaluation of learning difficulties.

METHOD

Hierarchical multiple regression analyses were used with the WISC-IV(UK) FSIQ (Block 1) and factor index scores (Block 2) as predictors and WIAT-II(UK) subtest and composite scores as dependent variables.

RESULTS

The WISC-IV(UK) FSIQ accounted for statistically significant and generally large portions of WIAT-II(UK) subtest and composite score variance. WISC-IV(UK) factor index scores combined to provide statistically significant increments in prediction of most WIAT-II(UK) subtest and composite scores over and above the FSIQ; however, the effect sizes were mostly small as previously observed (i.e., Canivez, 2013a, Psychol. Assess., 25, 484; Glutting et al., 2006, J. Spec. Educ., 40, 103; Nelson et al., 2013, Psychol. Assess., 25, 618). Individually, the WISC-IV(UK) factor index scores provided small unique contributions to predicting WIAT-II(UK) scores.

CONCLUSION

This, in combination with studies of apportioned variance from bifactor confirmatory factor analysis (Watkins et al., 2013, Int. J. Sch. Educ. Psychol., 1, 102), indicated that the WISC-IV(UK) FSIQ should retain the greatest weight in WISC-IV(UK) interpretation.

Exploratory Bifactor Analysis of the WJ-III Cognitive in Adulthood via the Schmid–Leiman Procedure

The Woodcock–Johnson-III cognitive in the adult time period (age 20 to 90 plus) was analyzed using exploratory bifactor analysis via the Schmid–Leiman orthogonalization procedure. The results of this study suggested possible overfactoring, a different factor structure from that posited in the Technical Manual and a lack of invariance across both age ranges under study. Even when forcing the seven-factor fit, the structure was problematic. The results from the 20 to 39 age group displayed patterns of convergence with and divergence from the Technical Manual’s structure. The results from the 40 and above age group were generally consistent with the Technical Manual’s structure except for retrieval fluency. This study is consistent with the body of exploratory factor analysis structural validity evidence suggesting that contemporary tests of cognitive ability, particularly those based on Cattell–Horn–Carroll theory, are overfactored and lack alignment with their respective Technical Manual’s presented structure.

Investigating the structure and invariance of the Wechsler Adult Intelligence Scales, Fourth Edition in a sample of adults with intellectual disabilities

Recent research has questioned whether the Wechsler Adult Intelligence Scales (WAIS) measure the same constructs for adults with intellectual disabilities as they do for the general population (MacLean et al., 2011). Using the special validity sample of the WAIS-IV (Wechsler, 2008b), the structure of the WAIS-IV was investigated using confirmatory factor analysis and tested for measurement invariance across a sample with intellectual disabilities and a control group matched in demographic characteristics. The instrument demonstrated strong factorial invariance when the standard subtests were used. When the standard and supplemental subtests were included in the model, the WAIS-IV four-factor structure provided a model of measurement for the Subtest Scores in the intellectual disability group, but the Perceptual Reasoning factor demonstrated differentiation into Fluid Reasoning and Visual-Spatial factors in the matched control group. In general, the research findings suggest that the four-factor structure of the WAIS-IV is invariant across the intellectual disability and matched control groups.

WAIS-IV and WISC-IV Structural Validity

Weiss, Keith, Zhu, and Chen (2013a) and Weiss, Keith, Zhu, and Chen (2013b), this issue, report examinations of the factor structure of the Wechsler Adult Intelligence Scale–Fourth Edition (WAIS-IV) and Wechsler Intelligence Scale for Children–Fourth Edition (WISC-IV), respectively; comparing Wechsler Hierarchical Model (W-HM) and Cattell–Horn–Carroll Hierarchical Model (CHC-HM), subtest cross-loadings, and factorial invariance between clinical and normative groups from the respective standardizations. Both studies suffer from a number of theoretical, methodological, and practical problems that significantly limit conclusions and recommendations for practitioner interpretations of these instruments. Additional analyses and research are required to better inform practitioners for WAIS-IV and WISC-IV use.

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.

Higher-order factor structures for the WISC-IV: implications for neuropsychological test interpretation

Factor-analytic studies support a hierarchical four-factor model for the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) with a prominent general, third-order factor. However, there is substantial disagreement on which type of higher-order model best fits the data and how different models should guide test interpretation in clinical practice, with many studies concluding interpretation should primarily be focused on general indicators of intelligence. We performed a series of confirmatory factor analyses with the WISC-IV standardization sample (N = 2,200, ages 6-16 years) to examine model fit and reexamined models used to support test interpretation at the general level. Consistent with previous research, bifactor models were difficult to identify; however, compared with bifactor and hierarchical models, the correlated factors model with no general higher-order factor provided the best fit to the data. Results from this study support the basic four-factor model specified in the WISC-IV technical manual, with test interpretation primarily focused at the factor level, rather than the general level suggested in previous studies.