Biomedical subjects

J F Rovet

Publications and source records attributed to J F Rovet.

At least 19 recordsLinked to original sources

PubMed2001

Effects of maternal occupational exposure to organic solvents on offspring visual functioning: a prospective controlled study.

BACKGROUND: Previous studies in adults and animals with high level exposure to organic solvents suggested impairments in visual functioning. The objective of this pilot study was to examine the effects of maternal occupational exposure to organic solvents during pregnancy on offspring color vision and visual acuity, the development of which may be especially vulnerable to organic solvent exposure. METHODS: We conducted a prospective cohort study of 32 offspring of women who were exposed occupationally to organic solvents during pregnancy compared with 27 nonexposed children. Monocular and binocular color vision and visual acuity were assessed using the Minimalist Test and the Cardiff Cards, respectively. Children with known hereditary color vision loss were excluded. RESULTS: Solvent-exposed children had significantly higher error scores on red-green and blue-yellow color discrimination, as well as poorer visual acuity compared with the control group. Exposure index (an estimated measure of exposure intensity) was not significantly related to color discrimination or visual acuity score. Despite excluding all children with a known family history of color vision loss, clinical red-green color vision loss was found among 3 of the 32 exposed children compared with none of the matched controls. CONCLUSIONS: These preliminary findings suggest that occupational exposure to organic solvents during pregnancy is associated with an increased risk of color vision and visual acuity impairment in offspring. The importance of routine visual function screening in risk assessment after prenatal exposure to chemicals warrants further attention.

Adult↗

PubMed2001

Neurophysiological correlates of verbal and nonverbal short-term memory in children: repetition of words and faces.

The neurophysiological correlates of verbal and nonverbal memory have been extensively studied in adults, but comparable investigations of children are limited. A memory paradigm that is well established with adults is the repetition task, which finds a positive shift in the ERP waveform in response to repeated items, called the "repetition effect." This is thought to represent the brain's memory trace for previously seen information and is reported predominantly at midline frontal and parietal electrodes. We recorded ERPs in thirteen 11- to 14-year old children during repetition tasks of words and faces. Performance was better and ERP latencies shorter for the word than the face task. Although a repetition effect similar to adults was seen at parietal electrodes with increased positivity to repeated items, increased negativity was observed at frontal electrodes; this suggests that the neural substrates of recognition memory continue to develop beyond 11 to 14 years of age. The demonstration of a repetition effect in children provides a basis for studying the neural correlates of specific childhood memory deficits.

Child↗

PubMed2001

Attention problems in adolescents with congenital hypothyroidism: a multicomponential analysis.

Even though early treatment of congenital hypothyroidism (CH) with newborn screening prevents the mental retardation previously seen in cretinism, affected children still exhibit subtle persisting neurocognitive deficits. One of their commonest problems is poor attention, which reflects both early disease severity and later (high) circulating thyroid hormone levels. While attention is currently regarded as multicomponential in nature, with different processing components supported by different brain regions, the specific components of attention affected by CH have not been identified. In light of animal evidence showing that neonatal thyroid hormone deficiencies impede the neurodevelopment of structures important for selective aspects of attention, we proposed a multicomponential approach to study attention in children with CH. This was accomplished via retrospective analysis of existing data on adolescents with CH whose attention was previously evaluated using multiple tests. Results showed significantly poorer overall attention in CH than controls with differences occurring mainly on focus and inhibit indices. However, performance on various indices was associated with different disease parameters. Poor encode and focus were correlated with more severe hypothyroidism and a longer period of thyroid hormone insufficiency and poor select and shift with higher thyroid hormone levels at testing. These results signify that thyroid hormone is important for the development and later regulation of brain structures supporting distinct aspects of attention.

Adolescent↗

PubMed2001

Dissociating attention deficits in children with ADHD and congenital hypothyroidism using multiple CPTs.

Recent studies suggest that children with different etiologies of attention disorder also differ as to the types of errors they make on attention tasks. Because these errors are reflective of the core deficits underlying their attention problems, we sought to compare error patterns in children with different attention disorders. Studied were 144 children aged 7-12 years, 43 with attention deficit hyperactivity disorder (ADHD), 35 with congenital hypothyroidism (CH), and 68 controls. Two variations of the continuous performance task (CPT) that differed in demands on inhibitory control and memory were used. One variation, the CPT:A-not-X task, required subjects to observe a continuous stream of letters shown at different rates on the computer screen and respond to all stimuli except "X". The other variation, the CPT:AX task, required them to respond whenever a specified combination of letter such as "A" followed by "X" appeared on the screen. On the CPT:A-not-X task, children with ADHD differed from controls in commission errors, signifying difficulty with inhibitory control, whereas children with CH differed in perceptual sensitivity or signal detection. Although the CH and ADHD groups both performed more poorly than controls on the CPT:AX task, children with CH made more errors to the first stimulus item, suggesting a problem holding information in memory, whereas children with ADHD made more errors to the second item, suggesting impulsivity. These results therefore signify the utility of these tasks in identifying the different mechanisms underlying the specific attention deficits of different groups of children.

Adolescent↗

PubMed2000

The effect of abnormal intrauterine thyroid hormone economies on infant cognitive abilities.

OBJECTIVE: To evaluate how intrauterine and neonatal thyroid hormone deficiencies affect infant cognitive abilities. METHOD: 26 infants with intrauterine or neonatal thyroid hormone deficiency and 20 full-term infants with normal thyroid economies were studied at 6 months of age or corrected age. Reasons for thyroid hormone deficiency were maternal hypothyroidism, maternal hyperthyroidism treated with antithyroid medication, congenital hypothyroidism, and low-risk prematurity. A computer-generated task during which infants' eye-movements were videotaped was used to assess attention, memory, and learning abilities RESULTS: Data from transcribed videotapes showed the study group was significantly less attentive and had longer reaction times than controls but did not differ on indices of sustaining attention or learning. Within thyroid-deficient groups, offspring of treated hyperthyroid mothers showed an atypical profile suggestive of hypervigilance. CONCLUSION: A decreased fetal or maternal thyroid hormone supply in pregnancy is associated with infants' poorer attention and altered rates of information processing.

Case-Control Studies↗

PubMed2000

Psychoeducational outcome in children with early-treated congenital hypothyroidism.

OBJECTIVES: To describe the psychoeducational characteristics of children with congenital hypothyroidism (CH) identified through newborn screening and to study changes over time. METHOD: Examined were 83 children with early-treated CH, who were long-time participants in a prospective study of outcome after newborn screening, and 120 control children who were classmates (n = 80) or siblings (n = 42). Children were tested during the third (53 children with CH and 46 control children) or the sixth (51 children with CH and 76 control children) grades at school with 21 children with CH being seen in both grades. Test instruments included multiple measures of achievement and cognitive abilities as well as behavior rating scales completed by parents and teachers. RESULTS: CH was associated with a slightly increased risk of learning disabilities in grade 3 but not grade 6. Third grade CH children scored lower than control children on tests of reading comprehension and arithmetic but did not differ on word recognition, writing, or spelling. Sixth grade CH children performed similar to controls on basic achievement tests but were reported to be doing poorer in several subject areas. For children with CH in grade 3, delayed skeletal maturity at diagnosis was associated with poorer word recognition ability and a longer period for normalizing thyroid hormone in infancy was correlated with weaker skill in learning sound-symbol correspondences. CONCLUSION: Early-treated CH is associated with mild delays in several basic achievement areas (reading comprehension and arithmetic) at the third grade level, with catch up by the sixth grade. However, as other findings indicate cognitive problems do persist into adolescence in memory, attention, and visuospatial processing areas, the implications of these deficits for other educational accomplishments needs additional follow-up.congenital hypothyroidism, thyroid hormone, newborn screening, achievement, behavior, attention.

Achievement↗

PubMed1999

The effect of hypoglycemic seizures on cognitive function in children with diabetes: a 7-year prospective study.

Sixteen children with insulin-dependent diabetes mellitus were evaluated at diagnosis and after 1, 3, and 7 years. They showed significant declines in verbal but not visuospatial abilities, particularly if they had any seizures from hypoglycemia. At the 7-year assessment those with hypoglycemic seizures showed deficits on perceptual, motor, memory, and attention tasks.

Adolescent↗

PubMed1999

Congenital hypothyroidism: long-term outcome.

Although mental retardation associated with congenital hypothyroidism (CH) is prevented by newborn screening and early treatment, affected children still undergo a brief period of thyroid hormone deficiency reflecting etiology of thyroid disease, illness severity, and treatment factors. Because thyroid hormone is essential for normal brain development and because some processes require thyroid hormone in the period when thyroid hormone was lacking, children with CH treated early may still have subtle neurocognitive deficits. As the period when thyroid hormone is needed differs for different brain regions, there may be different types of deficits depending on when thyroid hormone levels were insufficient. Since 1980, we have been following a large cohort of Toronto-based children with congenital hypothyroidism identified by newborn screening from infancy to adolescence. Early findings revealed a 5-10-point decline in IQ, poorer visuomotor and visuospatial abilities, delayed speech and language development, selective neuromotor deficiencies, and poorer attention and memory skills, which were correlated with different disease and treatment factors. Now a comparison between 48 subjects at adolescence and matched controls indicates that deficits persist in visuospatial, memory, and attention domains and these are correlated with severity of early hypothyroidism. Negative relationships between attention indices and thyroxine (T4) elevations at time of testing also suggest a role for thyroid hormone in the regulation of attention.

Brain↗

PubMed1999

Long-term neuropsychological sequelae of early-treated congenital hypothyroidism: effects in adolescence.

A cohort of over 100 children with congenital hypothyroidism (CH) detected via newborn screening was followed regularly throughout childhood and into adolescence. They were studied using a variety of different tests as part of three consecutive research components: semiannual/annual psychological assessments using age-appropriate intelligence tests (phase I), detailed psychoeducational evaluations in grades 3 and 6 (phase II) and a thorough neuropsychological evaluation during adolescence (phase III). Controls for phase I were siblings and for phase II, classmates and siblings. Phase III controls were drawn from a larger control pool and were individually matched with each CH case for age and gender. The results showed that although the CH group was intellectually functioning well within the normal range by adolescence, the children were performing significantly below expectation. Longitudinal analyses showed significant declines in IQ with age, signifying that the CH group was failing to make the same age-related gains as controls. Children with CH showed significantly poorer performance in visuospatial, language and fine motor areas as well as selective attention and memory deficits. At school, they were initially below par in arithmetic but were able to catch up by grade 6; however, their teachers reported that they were not performing as well as controls in the classroom and they demonstrated more difficulty with more complex school subjects such as science and social studies. Correlational analyses indicated different manifestations of early hypothyroidism versus later treatment factors, suggesting that while some effects can be improved by better treatment and management approaches, others caused by prenatal and perinatal thyroid hormone insufficiency may persist.

Adolescent↗

PubMed1998

Visual search for features and conjunctions in development.

Visual search performance was examined in three groups of children 7 to 12 years of age and in young adults. Colour and orientation feature searches and a conjunction search were conducted. Reaction time (RT) showed expected improvements in processing speed with age. Comparisons of RT's on target-present and target-absent trials were consistent with parallel search on the two feature conditions and with serial search in the conjunction condition. The RT results indicated searches for feature and conjunctions were treated similarly for children and adults. However, the youngest children missed more targets at the largest array sizes, most strikingly in conjunction search. Based on an analysis of speed/accuracy trade-offs, we suggest that low target-distractor discriminability leads to an undersampling of array elements, and is responsible for the high number of misses in the youngest children.

Adult↗

PubMed1997

Assessment of brain function in adolescent anorexia nervosa before and after weight gain.

This study assessed brain function in 20 adolescent females with anorexia nervosa (AN) and 20 controls using event-related potentials (ERPs) and a battery of neuropsychological tests. In the AN group, N4 latencies for a nonverbal memory task were significantly longer than for a verbal task, and P3 latencies for the verbal task were significantly longer among anorexics as compared to controls. On the nonverbal task, the AN group failed to show a right > left hemispheric asymmetry for P3 amplitudes which was observed for controls. These group differences for P3 latency and amplitude were particularly pronounced in the central-parietal region of the head. Body Mass Index (BMI) in the anorexic group significantly predicted N4 amplitudes for the verbal task in the left hemisphere and P3 amplitudes for the nonverbal task in the right hemisphere. The two groups did not differ on any of the tests used to assess neuropsychological functioning. Eight nutritionally recovered patients and their matched controls were retested using the same procedures. Anorexics showed larger P3 amplitudes for the verbal as compared to the nonverbal task at follow-up. These findings provide evidence for localized brain dysfunction in anorexia nervosa that only partially normalizes with weight gain.

Adolescent↗

PubMed1995

Long-term effects of L-thyroxine therapy for congenital hypothyroidism.

OBJECTIVE: To study the effects of initial and concurrent dose levels of L-thyroxine on ability and behavior in children with congenital hypothyroidism. METHODS: An existing database, involving a large cohort of children with congenital hypothyroidism detected by neonatal screening, was analyzed retrospectively. There were 94 children: 89 were assessed at age 7 years for intelligence and selective cognitive abilities, and 87 at age 8 years for behavior, achievement, and selective abilities. RESULTS: Subjects were stratified by median split into low and high starting dose groups. The high-dose group performed better on indexes of intelligence, verbal ability, and memory but had more behavior problems reflecting increased anxiety, social withdrawal, and poorer concentration. The dose of L-thyroxine at age 8 years was negatively correlated with memory task performance. CONCLUSION: A higher starting dose of L-thyroxine is beneficial for subsequent intellectual outcome in children with congenital hypothyroidism but may be associated with internalizing behavior problems.

Child↗

PubMed1993

Psychologic and psychoeducational consequences of thyroxine therapy for juvenile acquired hypothyroidism.

The observation of severe behavioral reactions or learning problems in three teenagers treated with L-thyroxine for juvenile acquired hypothyroidism prompted us to conduct a prospective study of achievement and behavioral characteristics of patients with newly diagnosed juvenile acquired hypothyroidism. On diagnosis of juvenile acquired hypothyroidism and before treatment with L-thyroxine, 23 children and adolescents underwent a comprehensive battery of psychoeducational tests, which was repeated after 3, 12, and 24 months of replacement therapy. Results revealed that adverse behavioral reactions and learning problems were relatively rare in these children, although symptoms of juvenile acquired hypothyroidism were associated with increased distractibility, hyperactivity, and poorer achievement. The least gain in achievement was made by children with more severe hypothyroidism at diagnosis; children with the best psychologic outcome were those who achieved euthyroidism more slowly. We conclude that severe behavioral manifestations of L-thyroxine therapy for juvenile acquired hypothyroidism are uncommon, but mild behavioral symptoms and poorer school achievement may occur in about 25% of patients, who represent the most severe cases at diagnosis.

Adolescent↗

PubMed1993

Psychoeducational characteristics of children and adolescents with insulin-dependent diabetes mellitus.

In recent years, researchers have observed selective neuropsychological impairment associated with insulin-dependent diabetes mellitus in childhood. At increased risk are children who develop diabetes before the age of 5, who experience severe hypo- and hyperglycemia, or who have frequent episodes of mild to moderate hypoglycemia. This article explores the existing literature to establish frequency and consistency of general and specific neurocognitive deficits in this pediatric patient population, as well as the impact of these deficits on school achievement and learning disabilities. Studies are integrated to identify contributing diabetes and nondiabetes factors. This is followed by a reanalysis of the data from two studies of diabetic children to determine the learning disability characteristics of this population and the factors contributing to dysfunctional school performance. Findings are discussed in terms of the impact of different factors reflecting adequacy of diabetes control on specific psychoeducational abilities.

Adolescent↗

PubMed1993

The psychoeducational characteristics of children with Turner syndrome.

Turner syndrome (TS) is a condition that affects 1 in 2,500 females due to a loss of some X chromosome material. It is characterized by a number of common physical features, including short stature, sexual infantilism, and infertility, as well as by specific learning and behavior problems. This article compares abilities, achievement, behavior, and self-esteem in 67 children with TS and 27 nonaffected controls. Results indicate selective impairments in visuospatial and memory areas and significant underachievement in arithmetic, particularly numerical ability, mental calculation, geometry, and reasoning. Learning problems, a major concern for parents, were not being satisfactorily addressed at school. Poor social competence and increased behavior problems, particularly in the area of hyperactivity, were also noted. Although self-esteem was only marginally lower, issues related to poor peer relations were most problematic.

Adolescent↗

PubMed1992

Neurodevelopment in infants and preschool children with congenital hypothyroidism: etiological and treatment factors affecting outcome.

Studied global intelligence and specific abilities of children from 1 to 5 years old, 108 with congenital hypothyroidism (CH) diagnosed by newborn screening and 71 sibling controls. Intelligence levels of the CH group were within the normal range but differed significantly from controls at age 5. CH demonstrated a language deficit at age 3, which diminished with age, as well as significantly poorer visuospatial and verbal skills at age 5. Children with absent thyroid glands or evidence of hypothyroidism in utero were outperformed by other CH children in most ability areas from 1 year on. Different components of ability were correlated with specific factors reflecting timing or duration of thyroid hormone deficiency, suggesting unique critical periods of thyroid hormone sensitivity for different specific cognitive abilities and their neural substrates. It is concluded that even though screened CH children are markedly improved by neonatal diagnosis, they are still at risk for subtle irreversible deficits, which depend on factors such as type, age at onset, and duration of disease.

Age Factors↗

PubMed1990

Does breast-feeding protect the hypothyroid infant whose condition is diagnosed by newborn screening?

Neuropsychological abilities at 1, 3, 5, and 6 years of age were compared in 107 children with congenital hypothyroidism identified by newborn screening who had been either breast-fed or formula fed during infancy. The thyroxine level was significantly higher in breast-fed children than formula-fed children at 1 and 2 months of age, but the level was not higher later during the first year of life. Controlling for parent IQ, socioeconomic status, and dose level, no differences in overall neuropsychological functioning were observed. Children with ectopic glands showed a significant advantage with breast-feeding on several tasks at 3 years of age. These results signify that thyroxine levels in infancy from breast-feeding are not necessarily reflected in improved intellectual functioning later in childhood.

Breast Feeding↗

PubMed1990

Growth in children with congenital hypothyroidism detected by neonatal screening.

A prospective analysis of physical growth in 56 children with congenital hypothyroidism compared the children's height, weight, and head circumference with population percentiles. Two measures of skeletal maturation and predictions of adult height were also compared with population standards. The mean percentiles for the children's height and head circumference were higher than population means. Although mean bone age scores were slightly higher, predictions of adult height did not differ significantly from midparental height (arithmetic mean of sum of parental heights) and population means. The duration of intrauterine hypothyroidism as measured by gestational bone age and the duration of postnatal hypothyroidism were inversely correlated with heights attained up to 9 years. This association suggests a possible long-term influence of early hypothyroidism on growth. In children with congenital hypothyroidism, maintenance of serum thyroxine levels in the upper half of the normal range results in normal growth patterns.

Age Determination by Skeleton↗