Seneste indlæg

30/06/2015

Our new paper is published online: Cognitive deficits at age 22 years associated with prenatal exposure to methylmercury

http://dx.doi.org/10.1016/j.cortex.2015.05.017

ABSTRACT
Prenatal exposure to mercury has been associated with adverse effects on child neurodevelopment.
The present study aims to determine the extent to which methylmercuryassociated
cognitive deficits persist into adult age. In a Faroese birth cohort originally
formed in 1986 – 1987 (N = 1,022), prenatal methylmercury exposure was assessed in terms
of the mercury concentration in cord blood and maternal hair. Clinical examinations of 847
cohort members at age 22 years were carried out in 2008 – 2009 using a panel of neuropsychological
tests that reflected major functional domains. Subjects with neurological
and psychiatric diagnoses were excluded from the data analysis, thus leaving 814 subjects.
Multiple regression analysis included covariates previously identified for adjustment.
Deficits in Boston Naming Test (BNT) and other tests of verbal performance were significantly
associated with the cord-blood mercury concentration. Deficits were also present in
all other tests applied, although most were not statistically significant. Structural equation
models were developed to ascertain the possible differences in vulnerability of specific
functional domains and the overall association with general intelligence. In models for
individual domains, all of them showed negative associations, with crystallized intelligence
being highly significant. A hierarchical model for general intelligence based on all
domains again showed a highly significant negative association with the exposure, with an
approximate deficit that corresponds to about 2.2 IQ points at a 10-fold increased prenatal
methylmercury exposure. Thus, although the cognitive deficits observed were smaller than
at examinations at younger ages, maternal diets with contaminated seafood were associated
with adverse effects in this birth cohort at age 22 years. The deficits affected major
domains of brain functions as well as general intelligence. Thus, prenatal exposure to this
marine contaminant appears to cause permanent adverse effects on cognition.

19/06/2015

Nyt om Woodcock-Johnson testsystemet

Woodcock-Johnson testsystemet for kognitive evner er verdenskendt, og er et af de bedste og nok det mest omfattende, der findes. Det bygger på moderne faktoranalytisk teori (CHC-teorien) og beskriver det fulde hierarki af menneskelige evner, sådan som de kan måles i store populationer. Således måles både den overordnede almene evnefaktor (g-faktoren) og de 8 – 10 underliggende brede evnedomæner, som f.eks. sproglig forståelse og almenviden, fluid ræsonnering, visuel forarbejdning, korttidshukommelse/arbejdshukommelse, langtidsgenkaldelse, kognitiv forarbejdningshastighed og auditiv forarbejdning, m.fl. Systemet er normeret i USA for mennesker fra 2 til 80 år.

Den fjerde udvidede og opdaterede version af testsystemet (WJ IV) kom i fjor. I min psykologprasis har den forrige version (WJ III) været brugt ved kliniske neuropsykologiske undersøgelser igennem årene som supplement til dansk-normerede testsystemer som WAIS III og WAIS IV. I den forskning, jeg har deltaget i på Færøerne om de negative evnemæssige følger af kviksølvforurenet havføde, indgik også delprøver fra WJ III i det samlede testbatteri ved undersøgelsen af en fødselskohorte på over 800 22-årige i årene 2008 – 2009. En ny artikel om disse resultater er på trapperne og udkommer snart i tidsskriftet Cortex.

Nu forlyder det, at fonden bag Woodcock-Johnson testsystemet, the Woodcock-Muñoz Foundation, overgår til et nyt Woodcock Institute for the Advancement of Neurocognitive Research and Applied Practice ved Texas Woman’s University (TWU) sammen med en stor donation på 10 millioner dollars til universitetet. Fremtidige licensafgifter for brug af testsystemet vil også tilfalde TWU. Parterne forventer herefter øget aktivitet både i klinisk praksis, i undervisning og i international forskning. Man må ønske dem held og lykke.

Læs nyheden og se en video

Det er en skam, at WJ testsystemet ikke i sin helhed er oversat til de skandinaviske sprog og er normeret i vort sprogområde. Hvis man bruger WJ systemet, må man forlade sig på de amerikanske normer. Det indebærer en vis risiko for skævhed (bias) i vurderingen i en dansk sammenhæng. Dog kan et velnormeret testsystem fra et andet industrialiseret land sommetider være at foretrække for tests med en svag national normering (f.eks. for få mennesker og svag repræsentativitet) eller enkelttests helt uden nogen normering.

 

18/06/2015

Gentagne mindre hovedskader kan give neuropsykologiske symptomer

Dette skyldes, at der kan opstå en forstærkende resonans i den menneskelige hjerne under acceleration af hovedet ved et traume.

I klinisk neuropsykologisk praksis, har jeg ofte været forundret over patienter med tilsyneladende alvorlige neuropsykologiske symptomer efter mindre hovedtraumer helt uden eller med kun en meget kort periode med koma. Hvis der efterfølgende ikke findes tydelige tegn på hjerneskade på en CT-scanning eller en MR-scanning, vil mange kolleger konkludere, at patienten må lide af en funktionel tilstand som dybest set indebærer, at det handler om psykodynamik. Det kan i mange tilfælde også være rigtigt, men måske kan et studie med en ny opdagelse som viser, at selv mindre hovedtraumer kan forårsage store resonerende bump i hjernen, give os en ny forståelse i nogle af disse sager.

Se en anmeldelse:

http://blogs.discovermagazine.com/d-brief/2015/06/09/brain-head-impacts/#.VXihrkbLIrh

Se abstrakt:

http://rsif.royalsocietypublishing.org/content/12/108/20150331

22/01/2014

Conference on human intelligence

The ISIR conference in Melbourne, Australia, December 12-14, 2013 was a most inspiring experience with great oral presentations and posters about many different aspects of human intelligence. The conference program with abstracts can be found here: http://www.isironline.org/meeting/.

My special interest in latent variable measurement models was satisfied mostly by a private talk with Dr. Gilles E. Gignac (http://drgillesgignac.blogspot.com.au/), who emphasises the importance of the bifactor model.

The importance of this model, also for clinical practice, is beautifully demonstrated in his and Dr. Watkins’ thought provoking new paper: Bifactor Modeling and the Estimation of Model-Based Reliability in the WAIS-IV  (see link below). The low reliability of the WAIS-IV indexes independent of g (e.g. after the g-variance is partialled out), will probably come as a surprise to many of my collegues, who often rely heavily on interpretation of index profiles and even on subtest profiles.

https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxkcmdpbGxlc2dpZ25hY3B1YmxpY2

27/06/2012

Official report on the study is out

The  hierarchical model described in the previous post was used in a study on: “Long Term Effects of Prenatal Exposure to  Pesticides“.

The report from “Miljøstyrelsen” (the Danish Environmental Protection Agency) can now be downloaded at: http://www2.mst.dk/Udgiv/publikationer/2012/06/978-87-92779-71-7.pdf.

The actual measurement model (before entering of covariates with effect on g) looks like this:

 

measurement-model

After correction for covariates there was a weak negative effect of prenatal pesticideexposure in girls alone. The negative effect was significant at level p = .03 in two-sided test.

There is an English summary in the report on pp. 11 – 14. An excerpt from the summary:

Effects on the nervous system
Overall, there were no significant effects of prenatal pesticide exposure on
children, but if the genders were analyzed separately, negative effects of
exposure were seen for the girls in most endpoints, although only significant
for language function, long-term memory and manual motor speed. For the
boys no negative effects on the results from the neuropsychological testswere
observed.

In a combined analysis model of the neuropsychological endpoints, we found
an overall negative effect of prenatal pesticide exposure on neuropsychological
function in girls but not in boys. Maternal pesticide exposure in early
pregnancy seems to have a negative effect on neurodevelopment, which was
detectable among girls but not among boys in the 6-11 years of age.

04/06/2011

Hierarchial model superior to multiple single-test analysis

In an ongoing analysis of psychometric test results from 176 children aged 6 to 11 years, half of whom may have been prenatally exposed to a certain category of environmental toxicants, the other half being control subjects, a hierarchical modelof intellectual abilities is superior to a multiple single-test analysis in detecting theadverse effect of toxicant exposure.

In the multiple single-test analysis only two of a greater number of tests (one verbal and the other manual motor) reached statistical significance for an adverse effect ofprenatal exposure (for girls only) after correction for covariates. Several of the other tests showed a tendency towards a negative effect, but none reached statistical significance.

A conclusion from this analysis  would only allow for negative effects on specific or  differential abilities in two different domains. The tendencies seen in other tests would not count. Furthermore one would have to express caution in accepting the validity of the results because of multiple statistical testing, and the consequent possibility of capitalizing on chance.

In a hierarchical model (established by confirmatory facor analysis – CFA) of the same tests, a statistically significant negative effect on the g-factor from prenatal exposure (in a structural equation modelSEM) could be demonstrated (for girls only) after correction for covariates.

hierarchical-model-2

Simplified hierarchical model of human cognitive abilities affected by toxicant

Presumably the greater purity of the latent variable, the g-factor, is the reason for this. In a hierarchical model true variance is extracted from all the manifest psychometric tests, while error variance is cancelled out. In addition the problem ofmultiple testing and capitalizing on chance is avoided, since only one statistical test is performed.

This analysis allows for the conclusion, that there is a negative effect on the general factor of the universe of human abilities. This is a much stronger conclusion, since the toxicant adversely affects a more general construct, and because the g-factor is known to be a strong predictor of success in a long time frame in real-life areas like education and occupation, and many others.

This example may serve as a recommendation for  adopting hierarchical models in epidemiological research, whenever effects on human mental abilities are examined.