Differences In IQ Scores Research Articles

Investigating changes in IQ scores over a decade in Brazil: factors at play.

This study aimed to determine whether the factors underlying potential differences between two birth cohorts, born in 1982 and 1993, influence the changes in IQ over time. Data from two Brazilian birth cohorts were used (1993 and 1982 Pelotas Birth Cohorts). The IQ scores were assessed using the WAIS-III test. Results showed that women born in 1993 had a higher average IQ score than those born in 1982, but no difference was found among men. The increase in IQ scores was only limited to participants from families with an income ranging from 1.1 to 3 times the minimum wage at the time of birth. The mean IQ score of participants born to mothers below the age of 20 remained stable over time, but increase for participants whose mothers were 20 years of age or older at the time of birth. This study emphasizes the importance of considering socio-economic and demographic factors when examining differences in IQ scores over time. Further research is needed to understand the underlying mechanisms of these findings.

International differences in the speed of cognitive development: A systematic examination of the existence of the Simber Effect

The Simber Effect refers to the phenomenon whereby, in Arabic countries, young children have an IQ that is little different from that of Western children but that these differences increase throughout childhood culminating in a difference of around 20 points by adulthood. The true nature of this phenomenon is revealed by an examination of 125 samples from all around the globe measured with Raven's Progressive Matrices. We show that in many cases different speeds of cognitive development increase the IQ score differences between countries mostly between 4 and 9 years of age, and that these increases can in part be explained by poor environmental conditions. However, the patterns are not completely clear, either in terms of regularity or strengths. Methodological problems, in particular the cross-sectional designs of the included samples, as well as the significance of the Simber Effect for country comparisons in intelligence are discussed.

IQ After Pediatric Concussion.

This study investigated IQ scores in pediatric concussion (ie, mild traumatic brain injury) versus orthopedic injury. Children (N = 866; aged 8-16.99 years) were recruited for 2 prospective cohort studies from emergency departments at children's hospitals (2 sites in the United States and 5 in Canada) ≤48 hours after sustaining a concussion or orthopedic injury. They completed IQ and performance validity testing postacutely (3-18 days postinjury; United States) or 3 months postinjury (Canada). Group differences in IQ scores were examined using 3 complementary statistical approaches (linear modeling, Bayesian, and multigroup factor analysis) in children performing above cutoffs on validity testing. Linear models showed small group differences in full-scale IQ (d [95% confidence interval] = 0.13 [0.00-0.26]) and matrix reasoning (0.16 [0.03-0.30]), but not in vocabulary scores. IQ scores were not related to previous concussion, acute clinical features, injury mechanism, a validated clinical risk score, pre- or postinjury symptom ratings, litigation, or symptomatic status at 1 month postinjury. Bayesian models provided moderate to very strong evidence against group differences in IQ scores (Bayes factor 0.02-0.23). Multigroup factor analysis further demonstrated strict measurement invariance, indicating group equivalence in factor structure of the IQ test and latent variable means. Across multisite, prospective study cohorts, 3 complementary statistical models provided no evidence of clinically meaningful differences in IQ scores after pediatric concussion. Instead, overall results provided strong evidence against reduced intelligence in the first few weeks to months after pediatric concussion.

Association between low fluoride exposure and children's intelligence: a meta-analysis relevant to community water fluoridation

ObjectivesPrevious meta-analyses have mainly focused on studies conducted in endemic fluorosis areas with relatively high fluoride concentrations. These are impoverished rural communities in China, India, and Iran, and the findings cannot be generalised to developed countries. Therefore, we investigated the association between fluoride concentrations relevant to community water fluoridation and children's cognition measured with IQ scores by synthesising effect sizes reported in observational studies. MethodsA previous meta-analysis and the National Toxicology Program database that included a search of multiple databases and the authors' search of PubMed, Google Scholar, and Mendeley provided the data. Cross-sectional and cohort studies examining the association between fluoride and children's cognition and intelligence scores were selected. Two reviewers abstracted data using standard procedures. We performed three meta-analyses to synthesise the effects using the random effects models. ResultsEight studies of standardized mean difference in IQ scores from non-endemic fluorosis areas found no statistically significant difference between recommended and lower levels of fluoride (standardized mean difference = 0.07; 95% confidence interval: −0.02, 0.17; I2 = 0%), and no significant fluctuation in IQ scores across the differences in fluoride concentrations by non-linear modeling with restricted cubic spline (P = 0.21). Meta-analyses of children's and maternal spot urinary fluoride associated pooled regression coefficients (Betachildren = 0.16; 95% confidence interval: −0.40, 0.73; P = 0.57; I2 = 0%, Betamaternal = −0.92; 95% CI: −3.29, 1.46; P = 0.45; I2 = 72%) were not statistically significant. Further regression analysis by standardizing absolute mean IQ scores from lower fluoride areas did not show a relationship between F concentration and IQ scores (Model Likelihood-ratio test: P-value = 0.34.) ConclusionsThese meta-analyses show that fluoride exposure relevant to community water fluoridation is not associated with lower IQ scores in children. However, the reported association observed at higher fluoride levels in endemic areas requires further investigation.

Similarities and differences in psycho-educational assessments of adolescents with specific language impairments and specific learning disabilities: A challenging differential diagnosis.

Specific Language Impairment (SLI) and Specific Learning Disabilities (SLD) have been the subject of extensive research especially with respect to the connection between them. However, the manifestation of these disorders in adolescence has not been thoroughly investigated. The objective of the present study was to compare the intelligence scores and the reading, oral and written language skills of Greek adolescents with SLI and Greek adolescents with SLD, as assessed during their psycho-educational evaluation, in order to clear the path for diagnosis and intervention. 124 Greek adolescents diagnosed with Specific Learning Disabilities and 76 Greek adolescents diagnosed with Specific Language Impairment aged from 11 to 16 years took part in the study. All participants were assessed in reading, oral language and written language skills and took part in IQ testing. Independent samples t-test, chi-square test, odds ratios and their 95 percent confidence intervals were implemented to determine statistically significant differences. Analyses revealed differences in IQ scores and some differences in the skills assessed, thus indicating that SLI adolescents exhibited more difficulties across most of the basic academic skills, whereas SLD adolescents' difficulties confined to the affected written language skills. Specifically, the observed difference was statistically significant for the total and verbal IQ score, and WISC-III scores also disclosed a significant difference for the similarities and information defisub- tests. Regarding reading skills, SLI adolescents were 4.9 times more likely to exhibit line skipping, 5.8 times more likely to exhibit hesitations, 3.2 times more likely to exhibit repetitions of syllables/words/ phrases, and 8.5 times more likely to exhibit non-acknowledgement of punctuation. Regarding reading comprehension, adolescents with SLI were more likely to have difficulty in retrieving simple information questions, making inferences, and giving titles. Adolescents with SLI were also more likely to have difficulties in story reproduction, giving synonyms/opposites, oral sentence reproduction and auditory oral word reproduction. In the area of written language skills, SLI adolescents were more likely to have poor handwriting, poor content, poor structure, and poor use of punctuation. In adolescence, Specific Language Impairment can be a different manifestation of an ongoing language disorder, which finally appears as a different type of Specific Learning Disability, but with a more generalized nature of learning difficulties. This finding should be interpreted in terms of the importance of differential diagnosis, especially during the challenging period of adolescence.

Mediators of IQ test score differences across racial and ethnic groups: The case for environmental and social justice

Mediators of IQ score differences of Whites with Hispanics and African Americans are reviewed in the WISC-IV, WISC-V, and WAIS-IV. Mediators included parent education, income and academic expectations for children and adolescents, and self-education, income and occupation for adults. Results showed that these variables account for substantial portions of variance in all group comparisons, but least for African Americans and adults. The critical influence of cognitively enriching and impoverishing environments on the neurocognitive development of children, and the unequal distribution of these influences across social and economic groups are discussed as complementary with interpretations of acculturation and heredity.

Effect of Long-Chain Polyunsaturated Fatty Acids in Infant Formula on Cognitive Function Beyond Infancy: A Systematic Review and Meta-Analysis of Randomised Controlled Trials

Background: Supplementation of infant formula with long-chain polyunsaturated fatty acids (LCPUFA) is now standard practice, but clear evidence from randomised controlled trials (RCT) of functional benefits is lacking. Methods: We performed a systematic review and meta-analysis of published and unpublished data from RCTs that compared infant formula with and without LCPUFA. We determined the effect of LCPUFA-supplementation on standardised assessments of cognitive function after the age of 2·5 years. We used fixed-effects meta-analyses to compare mean differences in intelligence scores, for participants born at term and preterm. This study is registered with PROSPERO. Findings: We included eight RCTs that randomised participants between 1982 and 2004. The age at the last available cognitive test ranged from 3·3 to 16 years. The pooled mean difference in IQ score from four trials in term-born children was consistent with a lower IQ score in LCPUFA-supplemented compared with unsupplemented groups: pooled mean difference -2·87 points (95% CI -5·74,-0·01). Two trials in preterm-born children found no detectable difference in IQ score between groups: pooled mean difference -1·88 (-6·04, 2·29). Overall study quality was low, partly due to high losses to follow-up. Interpretation: We found no evidence of benefit and weak evidence that LCPUFA-supplementation reduced IQ score in term-born children, though at borderline significance. These findings are relevant to regulators of infant formula when considering whether any evidence of benefit outweighs the potential disadvantages for cognitive function. Funding: Economic and Social Research Council UBEL DTP studentship. Declaration of Interest: M. Verfurden, S. Dib and Dr. Gilbert and Dr. Jerrim declare no competing interests. Dr. Fewtrell was involved in data analysis and publication of randomised trials of LCPUFA-supplemented infant formulas funded by grants from Numico Res BV and Heinz UK. The companies also provided the infant formulas for the studies. She was also involved in follow-up studies (including cognitive outcome) of children and adolescents from randomised trials of LCPUFA-supplemented formulas, with funding from the Medical Research Council and European Union (FP6-FOOD-2005-007036). She has been a member of Infant Nutrition Working Group at EFSA (European Food Safety Authority) since 2013.

Prenatal exposure to non-steroidal anti-inflammatory drugs (NSAIDs) and neurodevelopmental outcomes in children.

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used during pregnancy. Findings that prenatal NSAID exposure may affect offspring neurodevelopment have been inconsistent. We investigated the effect of prenatal NSAID exposure on childhood neurodevelopment and explored the susceptibility of our effect estimates to forms of bias via negative exposure, negative outcome, and multi-informant analyses. In a cohort of pregnant women (n=6876), perinatal NSAID use was assessed by prescriptions and self-report. Primary neurodevelopmental outcomes included attention problems using maternal reports at 1½, 3, and 5years. To explore potential systematic biases, we compared estimates from maternally reported attention problems to a teacher's report and a measure of nonverbal intelligence assessed at a clinic visit at age 6years; we also used NSAID use before pregnancy and somatic problems as a "negative" exposure and outcome, respectively. Maternal reports suggested that prenatal exposure to NSAIDs was associated with more attention problems at younger ages (eg, at age 3: mean difference in attention problems score: 0.30; 95% CI 0.12, 0.48). However, no strong association with attention problems was found in the teacher report, and a similarly strong association between prenatal NSAID exposure and somatic complaints suggests residual confounding by indication likely remains. Moreover, prenatal exposure to NSAIDs was not associated with an observed measure of IQ (mean difference in IQ score: -0.32; 95% CI: -1.82, 1.19). Jointly, our results suggest that the observed associations between prenatal exposure to NSAIDs and child attention problems reflect systematic biases of a null or small effect.

Long term cognitive outcomes of early term (37-38 weeks) and late preterm (34-36 weeks) births: A systematic review.

Background: There is a paucity of evidence regarding long-term outcomes of late preterm (34-36 weeks) and early term (37-38 weeks) delivery. The objective of this systematic review was to assess long-term cognitive outcomes of children born at these gestations. Methods: Four electronic databases (Medline, Embase, clinicaltrials.gov and PsycINFO) were searched. Last search was 5 th August 2016. Studies were included if they reported gestational age, IQ measure and the ages assessed. The protocol was registered with the International prospective register of systematic reviews (PROSPERO Record CRD42015015472). Two independent reviewers assessed the studies. Data were abstracted and critical appraisal performed of eligible papers. Results: Of 11,905 potential articles, seven studies reporting on 41,344 children were included. For early term births, four studies (n = 35,711) consistently showed an increase in cognitive scores for infants born at full term (39-41 weeks) compared to those born at early term (37-38 weeks) with increases for each week of term (difference between 37 and 40 weeks of around 3 IQ points), despite differences in age of testing and method of IQ/cognitive testing. Four studies (n = 5644) reporting childhood cognitive outcomes of late preterm births (34 - 36 weeks) also differed in study design (cohort and case control); age of testing; and method of IQ testing, and found no differences in outcomes between late preterm and term births, although risk of bias was high in included studies. Conclusion: Children born at 39-41 weeks have higher cognitive outcome scores compared to those born at early term (37-38 weeks). This should be considered when discussing timing of delivery. For children born late preterm, the data is scarce and when compared to full term (37-42 weeks) did not show any difference in IQ scores.

Changes in water manganese levels and longitudinal assessment of intellectual function in children exposed through drinking water

BackgroundManganese is commonly found in water but potential neurotoxic effects from exposure through drinking water are poorly understood. We previously reported a cross-sectional study showing that drinking water Mn concentration was associated with lower IQ in children aged 6 to 13 years. ObjectiveFor this follow-up study, we aimed to re-assess the relation between exposure to Mn from drinking water and IQ at adolescence. In addition, we aimed to examine whether changes in drinking water Mn concentration was associated with changes in IQ scores. MethodsFrom the 380 children enrolled in the baseline study, 287 participated to this follow-up study conducted in average 4.4 years after. Mn concentration was measured in home tap water and children's hair. The relationships between these Mn exposure indicators and IQ scores (Weschsler Abbreviated Scale of Intelligence) at follow-up were assessed with linear regression analysis, adjusting for potential confounders. Intra-individual differences in IQ scores between the two examinations were compared for children whose Mn concentration in water remained stable between examinations, increased or decreased. ResultsThe mean age at follow-up was 13.7 years (range, 10.5 to 18.0 years). Geometric mean of Mn concentration in water at follow-up was 14.5μg/L. Higher Mn concentration in water measured at follow-up was associated with lower Performance IQ in girls (β for a 10-fold increase=−2.8, 95% confidence intervals [CI] −4.8 to −0.8) and higher Performance IQ in boys (β=3.9, 95% CI 1.4 to 6.4). IQ scores were not significantly associated with Mn concentration in hair, although similar trends as for concentration in water were observed. For children whose Mn concentration in water increased between baseline and follow-up, Performance IQ scores decreased significantly (intra-individual difference, −2.4 points). ConclusionHigher levels of Mn in drinking water were associated with lower Performance IQ in girls, whereas the opposite was observed in boys. These findings suggest long-term exposure to Mn through drinking water is associated differently with cognition in boys and girls.

Are Shunt Revisions Associated with IQ in Congenital Hydrocephalus? A Meta -Analysis.

Although it is generally acknowledged that shunt revisions are associated with reductions in cognitive functions in individuals with congenital hydrocephalus, the literature yields mixed results and is inconclusive. The current study used meta-analytic methods to empirically synthesize studies addressing the association of shunt revisions and IQ in individuals with congenital hydrocephalus. Six studies and three in-house datasets yielded 11 independent samples for meta-analysis. Groups representing lower and higher numbers of shunt revisions were coded to generate effect sizes for differences in IQ scores. Mean effect size across studies was statistically significant, but small (Hedges' g=0.25, p<0.001, 95% CI [0.08, 0.43]) with more shunt revisions associated with lower IQ scores. Results show an association of lower IQ and more shunt revisions of about 3 IQ points, a small effect, but within the error of measurement associated with IQ tests. Although clinical significance of this effect is not clear, results suggest that repeated shunt revisions because of shunt failure is associated with a reduction in cognitive functions.

Association Between a Single General Anesthesia Exposure Before Age 36 Months and Neurocognitive Outcomes in Later Childhood.

Exposure of young animals to commonly used anesthetics causes neurotoxicity including impaired neurocognitive function and abnormal behavior. The potential neurocognitive and behavioral effects of anesthesia exposure in young children are thus important to understand. To examine if a single anesthesia exposure in otherwise healthy young children was associated with impaired neurocognitive development and abnormal behavior in later childhood. Sibling-matched cohort study conducted between May 2009 and April 2015 at 4 university-based US pediatric tertiary care hospitals. The study cohort included sibling pairs within 36 months in age and currently 8 to 15 years old. The exposed siblings were healthy at surgery/anesthesia. Neurocognitive and behavior outcomes were prospectively assessed with retrospectively documented anesthesia exposure data. A single exposure to general anesthesia during inguinal hernia surgery in the exposed sibling and no anesthesia exposure in the unexposed sibling, before age 36 months. The primary outcome was global cognitive function (IQ). Secondary outcomes included domain-specific neurocognitive functions and behavior. A detailed neuropsychological battery assessed IQ and domain-specific neurocognitive functions. Parents completed validated, standardized reports of behavior. Among the 105 sibling pairs, the exposed siblings (mean age, 17.3 months at surgery/anesthesia; 9.5% female) and the unexposed siblings (44% female) had IQ testing at mean ages of 10.6 and 10.9 years, respectively. All exposed children received inhaled anesthetic agents, and anesthesia duration ranged from 20 to 240 minutes, with a median duration of 80 minutes. Mean IQ scores between exposed siblings (scores: full scale = 111; performance = 108; verbal = 111) and unexposed siblings (scores: full scale = 111; performance = 107; verbal = 111) were not statistically significantly different. Differences in mean IQ scores between sibling pairs were: full scale = -0.2 (95% CI, -2.6 to 2.9); performance = 0.5 (95% CI, -2.7 to 3.7); and verbal = -0.5 (95% CI, -3.2 to 2.2). No statistically significant differences in mean scores were found between sibling pairs in memory/learning, motor/processing speed, visuospatial function, attention, executive function, language, or behavior. Among healthy children with a single anesthesia exposure before age 36 months, compared with healthy siblings with no anesthesia exposure, there were no statistically significant differences in IQ scores in later childhood. Further study of repeated exposure, prolonged exposure, and vulnerable subgroups is needed.

Does Congenital Heart Disease Affect Neurodevelopmental Outcomes in Children with Down Syndrome?

The impact that congenital heart disease (CHD) has on the neurodevelopment of children with Down syndrome (DS) is unknown and potentially has implications for targeted early intervention. This study assessed the relationship between CHD that required surgery in the first year of life and neurodevelopmental, behavioral and emotional functioning outcomes in children with DS. A retrospective chart review of 1092 children (0-18 years) with DS who visited a single institution from 8/08-8/13 was performed. Children who underwent at least one of nine neurodevelopmental (cognitive, language, developmental) or academic tests were included in the analysis (N = 178). Cohort was age-divided into infants/toddlers (0-2 years), preschoolers (3-5 years), and school age/adolescent (6-18 years). Test scores of children with DS who underwent cardiac surgery in the first year of life were compared to children with DS without CHD. T test, chi-square and Mann Whitney U tests were used where appropriate. Infants/toddlers with cardiac surgery had lower scores for receptive (P = .01), expressive (P = .021) and composite language (P < .001) compared to those with no CHD. Preschoolers with cardiac surgery had lower language scores and lower visual motor scores, although not statistically significant. In school age children with cardiac surgery there were no differences in IQ scores, language scores, or academic achievement scores compared to those without CHD. Also at school-age there was no difference in the incidence of ADHD, executive function or on internalizing and externalizing behavior scores. Children with DS undergoing cardiac surgery during the first year demonstrated poorer neurodevelopmental outcomes as infants/toddler but had no difference at school age compared to children with DS without CHD. These results will guide early interventions to optimize neurodevelopmental outcomes in children with DS and will help with family counseling after CHD repair.

Using Score Equating and Measurement Invariance to Examine the Flynn Effect in the Wechsler Adult Intelligence Scale

The Flynn effect (FE; i.e., increase in mean IQ scores over time) is commonly viewed as reflecting population shifts in intelligence, despite the fact that most FE studies have not investigated the assumption of score comparability. Consequently, the extent to which these mean differences in IQ scores reflect population shifts in cognitive abilities versus changes in the instruments used to measure these abilities is unclear. In this study, we used modern psychometric tools to examine the FE. First, we equated raw scores for each common subtest to be on the same scale across instruments. This enabled the combination of scores from all three instruments into one of 13 age groups before converting raw scores into Z scores. Second, using age-based standardized scores for standardization samples, we examined measurement invariance across the second (revised), third, and fourth editions of the Wechsler Adult Intelligence Scale. Results indicate that while scores were equivalent across the third and fourth editions, they were not equivalent across the second and third editions. Results suggest that there is some evidence for an increase in intelligence, but also call into question many published FE findings as presuming the instruments' scores are invariant when this assumption is not warranted.

Особенности полового диморфизма когнитивных способностей и структуры интересов подростков с высоким уровнем интеллекта

We present the results of the study of age dynamics factors of the intellectual abilities of cognitively gifted adolescents, namely manifestations of sexual dimorphism in their intellectual sphere and interests. We described an empirical testing of the hypothesis of the specifics of sexual dimorphism of intellectual abilities of adolescents with a high IQ. The study involved 249 adolescents (St. Petersburg), aged 14-17 years, including 132 adolescent high IQ - 81 girl and 51 boy, 117 adolescents with an average IQ - 66 girls and 51 boy. Intellectual performance (11 faculties - spatial, verbal, math, memory) are measured by the Universal intelligence test, the interests – with a biographical questionnaire. Mathematical processing of data was performed using SPSS Statistics 20. The study showed sexual dimorphism abilities manifested in adolescents with high IQ: girls outperform boys in verbal (p = 0.001), spatial (p = 0.05), mnemonic abilities (p = 0.001) and in general, IQ (r = 0.05); boys outperform girls in mathematical abilities (p = 0.001). No differences were found in adolescents with average IQ. Differences in IQ scores of boys and girls with high IQ were similar to the structure of the differences in their interests. We suggested an especially "sensitive" development abilities of teenagers with a high IQ to the structure of interest.

Examining the effects of dopamine genes on verbal IQ within and between families

Although research findings have revealed that both genetic and environmental factors contribute to variation in IQ at the individual level, no studies have examined how genetic differences contribute to differences in IQ within and between families. The current study uses data drawn from the National Longitudinal Study of Adolescent Health (Add Health) to examine the potential role genetic factors play in shaping differences in IQ scores within and between families. The results revealed that while genetic variation between family members did not significantly predict differences in IQ scores, family-level dopaminergic risk scores did significantly predict differences in family-level IQ. The implications of the results are elaborated upon, and suggestions for future research are discussed.

Editor’s Choice

Editor’s Choice

Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis

Background: Although fluoride may cause neurotoxicity in animal models and acute fluoride poisoning causes neurotoxicity in adults, very little is known of its effects on children’s neurodevelopment.Objective: We performed a systematic review and meta-analysis of published studies to investigate the effects of increased fluoride exposure and delayed neurobehavioral development.Methods: We searched the MEDLINE, EMBASE, Water Resources s, and TOXNET databases through 2011 for eligible studies. We also searched the China National Knowledge Infrastructure (CNKI) database, because many studies on fluoride neurotoxicity have been published in Chinese journals only. In total, we identified 27 eligible epidemiological studies with high and reference exposures, end points of IQ scores, or related cognitive function measures with means and variances for the two exposure groups. Using random-effects models, we estimated the standardized mean difference between exposed and reference groups across all studies. We conducted sensitivity analyses restricted to studies using the same outcome assessment and having drinking-water fluoride as the only exposure. We performed the Cochran test for heterogeneity between studies, Begg’s funnel plot, and Egger test to assess publication bias, and conducted meta-regressions to explore sources of variation in mean differences among the studies.Results: The standardized weighted mean difference in IQ score between exposed and reference populations was –0.45 (95% confidence interval: –0.56, –0.35) using a random-effects model. Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas. Subgroup and sensitivity analyses also indicated inverse associations, although the substantial heterogeneity did not appear to decrease.Conclusions: The results support the possibility of an adverse effect of high fluoride exposure on children’s neurodevelopment. Future research should include detailed individual-level information on prenatal exposure, neurobehavioral performance, and covariates for adjustment.

The impact of therapy for childhood acute lymphoblastic leukaemia on intelligence quotients; results of the risk-stratified randomized central nervous system treatment trial MRC UKALL XI

BackgroundThe MRC UKALLXI trial tested the efficacy of different central nervous system (CNS) directed therapies in childhood acute lymphoblastic leukaemia (ALL). To evaluate morbidity 555/1826 randomised children underwent prospective psychological evaluations. Full Scale, verbal and performance IQs were measured at 5 months, 3 years and 5 years. Scores were compared in; (1) all patients (n = 555) versus related controls (n = 311), (2) low-risk children (presenting white cell count (WCC) < 50 × 109/l) randomised to intrathecal methotrexate (n = 197) versus intrathecal and high-dose intravenous methotrexate (HDM) (n = 202), and (3) high-risk children (WCC ≥ 50 × 109/l, age ≥ 2 years) randomised to HDM (n = 79) versus cranial irradiation (n = 77).ResultsThere were no significant differences in IQ scores between the treatment arms in either low- or high-risk groups. Despite similar scores at baseline, results at 3 and 5 years showed a significant reduction of between 3.6 and 7.3 points in all three IQ scores in all patient groups compared to controls (P < 0.002) with a higher proportion of children with IQs < 80 in the patient groups (13% vs. 5% at 3 years p = 0.003).ConclusionChildren with ALL are at risk of CNS morbidity, regardless of the mode of CNS-directed therapy. Further work needs to identify individuals at high-risk of adverse CNS outcomes.Trial registrationISRCTN: ISRCTN16757172

Meta-analysis of the association between preterm delivery and intelligence

An increasing proportion of infants are born preterm, and their survival has improved. Therefore, their long-term sequelae are of increasing public health importance. We conducted a systematic review covering a 30 year period (1980-2009). A random effects meta-analysis provided a pooled estimate of the difference in IQ score between individuals born preterm and term. Small-study bias was examined using a funnel plot and Egger's test, and meta-regression was used to investigate possible causes of heterogeneity. Cumulative meta-analysis was used to determine if the magnitude of the association had changed over time. The 27 eligible studies covered 7044 individuals; 3504 (50%) delivered preterm and 3540 (50%) at term. They provided 37 estimates of difference in IQ. All demonstrated a reduced IQ among those delivered preterm and all but four reached statistical significance. Overall, IQ score was 11.94 (95% CI: 10.47-13.42, P < 0.001) points lower among children born preterm. There was moderate heterogeneity (overall I(2) 74.2%, P < 0.001), but no significant small-study bias (P = 0.524). The association between preterm delivery and IQ did not change significantly over time. There was a statistically significant, linear association across the gestational age range (adjusted coefficient: -0.91, 95% CI: -1.64, -0.17, P = 0.018). There is a strong and consistent body of evidence suggesting an association between preterm delivery and reduced IQ, with evidence of a dose-response relationship with gestational age.