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Biomedical subjects

C Derom

Publications and source records attributed to C Derom.

At least 19 recordsLinked to original sources
PubMed2002

Prenatal life and post-natal psychopathology: evidence for negative gene-birth weight interaction.

BACKGROUND: Many studies suggest that pregnancy and birth complications (PBCs) are environmental risk factors for child psychopathology. However, it is not known whether the effects of PBCs occur independently of genetic predisposition. The current study examined the possibility of gene-environment interaction in a twin design. METHOD: The East Flanders Prospective Twin Survey prospectively records the births of all twin pairs born in East Flanders, Belgium. The current study included 760 twin pairs aged 6-17 years. Multilevel regression analysis was used to assess the effects of several PBCs collected around the time of birth. Using structural equation modelling, ACE models assuming additive genetic (A), shared environmental (C) and unique environmental (E) influences, were compared in order to examine whether the contribution of genetic factors to parent-rated child problem behaviour varied as a function of exposure to dichotomously and continuously defined PBCs. RESULTS: A main independent effect of lower birth weight, corrected for gestational age (small for gestational age--SGA), on child problem behaviour was found. In addition, there was an interaction between genetic influence and SGA, in that being smaller for gestational age resulted in less influence of additive genetic factors on individual differences in problem behaviour. CONCLUSIONS: Results are suggestive of negative gene-birth weight interaction. Children who are SGA are less sensitive to the genetic effects, and those with high genetic vulnerability are less sensitive to the effects of being SGA in bringing about post-natal mental health effects.

Adolescent↗
PubMed2002

Child psychopathology and lower cognitive ability: a general population twin study of the causes of association.

Previous work has demonstrated associations between lower cognitive ability and childhood and adult non-psychotic psychopathology. As both cognitive ability (CA) and child psychopathology (CP) are influenced by genetic factors, one explanation for the association is that they are the pleiotropic manifestations of the same underlying genetic factors. The present paper examines three possible causes of the association: additive genetic factors, common environmental factors and individual-specific environmental factors. Three hundred and seventy-six twin pairs from the East Flanders Prospective Twin Survey were examined with the Child Behaviour Checklist and the Wechsler Intelligence Scale for Children-Revised. The cross-twin within-variable, within-twin cross-variable and cross-twin cross-variable correlations were calculated. Using structural equation modelling, bivariate models were fitted. The best fitting model was chosen, based on likelihood and parsimony. The observed phenotypic correlation between CP and CA was -0.19 (95% CI: -0.09, -0.27), with genetic factors accounting for about 84% of the observed correlation. Bivariate model fitting quantified the genetic correlation between CP and CA at -0.27 (95% CI: -0.12, -0.42) and the individual-specific environmental correlation at -0.17 (95% CI: -0.03, -0.31). In children, three different genetic factors may exist: one that solely affects the liability to CP, one that has only an effect on CA and one that influences both CP and CA. While individual-specific environmental factors can influence the liability to both traits, our results suggest that most of the environmental factors that increase the risk of CP do not influence CA and vice versa.

Adolescent↗
PubMed2001

A prospective twin study of birth weight discordance and child problem behavior.

BACKGROUND: We investigated whether low birth weight constitutes a causal risk factor for child problem behavior, using a variation of the co-twin control method. METHODS: In a representative sample of 745 twin pairs (monozygotic: 324 pairs), birth weight was recorded at birth and child problem behavior at mean age 10 years was measured with the Child Behaviour Checklist (CBCL). RESULTS: Lower birth weight was a continuous risk factor for later child problem behavior (adjusted regression coefficient over units of 500 g: beta = -.15, p =.046), and greater levels of within-pair CBCL discordance did not result in a reduced effect size. Greater within-pair birth weight discordance was associated with greater within-pair CBCL score discordance (beta =.35, p <.001). This latter effect was similar in monozygotic (beta =.34, p =.005) and dizygotic twins (beta =.37, p =.003). CONCLUSIONS: The fact that (1) the effect size of the association between low birth weight and child problem behavior was not reduced in pairs with greater levels of CBCL discordance, and (2) similar effect sizes were found in monozygotic and dizygotic twins for the within-pair association between birth weight discordance and CBCL score discordance, suggests that the observed relationship between low birth weight and child problem behavior is not due to a shared environmental or genetic variable that influences both characteristics. Lower birth weight is a causal risk factor for child problem behavior, the effects of which may well extend into adulthood.

Adolescent↗
PubMed2001

Birth weight and blood pressure in young adults: a prospective twin study.

BACKGROUND: The intrauterine environment may be a critical period for the development of hypertension in later life. In the present study, we applied the twin approach to estimate the contribution of genetic and environmental causes that may underlie the birth weight-adult blood pressure association. METHODS AND RESULTS: Birth weights of 418 twin pairs were obtained prospectively, and resting and 24-hour ambulatory blood pressures were obtained at the age of 18 to 34 years. In women, resting systolic blood pressure decreased 4.27 mm Hg (P<0.001) and diastolic pressure decreased 2.18 mm Hg (P=0.02) per kilogram increase in birth weight. Similar associations were found for ambulatory measurements, although these were somewhat less pronounced. Pair-wise analysis confirmed these findings: twin pairs of whom both members had a low birth weight (<2500 g) had a higher systolic blood pressure compared with twins who both had a high birth weight (>/=2500 g). Systolic blood pressure of the lightest of a low-birth-weight pair was >/=4.7 mm Hg (P=0.02) higher and of the heaviest >/=2.4 mm Hg higher (P=0.2) than similar measurements in high-birth-weight pairs. Intrapair differences in blood pressure between the lightest and the heaviest at birth were only present in low-birth-weight pairs. The results were similar for monozygotic and dizygotic twin pairs. In men, no associations were found between birth weight and adult blood pressure. CONCLUSIONS: These findings suggest that prenatal programming of adult blood pressure occurs at least in female twins. We suggest that particularly maternal influences, experienced by both twin members, may underlie the association between birth weight and blood pressure. The fetoplacental unit seems to influence blood pressure only when both fetuses had low birth weight.

Adolescent↗
PubMed2001

Length of gestation and birthweight in dizygotic twins.

Despite the longer gestation of girls, their birthweight is less than that of boys. Because unlike-sex twins provide a natural situation in which to investigate the influence of sex on gestation, we compared birthweight and gestation of 1929 same-sex and unlike-sex dizygotic pairs. Length of gestation in unlike-sex pairs was similar to that of female same-sex pairs, and significantly (0.4 weeks; p=0.02) longer than that of male same-sex pairs. Birthweight of girls from unlike-sex pairs was similar to that of girls from same-sex pairs, but boys from unlike-sex pairs weighed 78 g more than boys from same-sex pairs (p=0.001). These data show that in unlike-sex pairs it is the girl that prolongs gestation for her brother, resulting in a higher birthweight than that of same-sex boys.

Analysis of Variance↗
PubMed2001

Associations between nonshared environment and child problem behaviour.

BACKGROUND: Twin studies suggest that environmental effects on the development of child psychopathology largely involve nonshared environmental processes. However, the influence of the nonshared environment may have been overestimated, as the relationship between environment and behaviour may be genetically mediated. A direct measure of the nonshared environment (using the Sibling Inventory of Differential Experience - SIDE) was investigated in relation to child psychopathology, and tested for possible genetic mediation. METHOD: Parent-rated versions of the Child Behaviour Checklist (CBCL) and the SIDE were collected in 760 twin pairs aged 6-17 years. Multilevel regression analysis was used to assess the influence of SIDE scores on CBCL total problem scores, internalising symptoms, externalising symptoms and depressive symptom scores. Genetic mediation was assessed by examining interaction with zygosity in the association between SIDE scores and differences in CBCL scores (absence of interaction indicating no genetic mediation). RESULTS: The results revealed significant associations between SIDE dimensions on the one hand, and degree of internalising, externalising, depression and total symptom scores on the other. However, the effects were non-linear, and especially apparent for the extremes of differential environmental experience within twin pairs. Overall, there was no strong evidence for genetic mediation of associations between nonshared environment and symptoms. CONCLUSIONS: Direct, genetically unconfounded but skewed relationships may exist between nonshared environment on the one hand and behavioural differences on the other, although longitudinal data are necessary to determine the direction of effects.

Adolescent↗
PubMed2001

Heritability estimates of intelligence in twins: effect of chorion type.

This study investigates the basic assumption of homogeneity of monozygotic (MZ) twins: are there differences according to the timing of the zygotic splitting, early in dichorionic (DC) and later in monochorionic (MC) pairs? We assessed the IQ of 451 same-sexed twin pairs of known zygosity and chorion type with the Wechsler Intelligence Scale for Children-Revised (WISC-R). The variances of within-pair differences were compared for monochorionic (MC), dichorionic monozygotic (DC-MZ) and dizygotic same-sexed (DZ) twins and structural equation modeling was applied. High heritability estimates were found for almost all subscales and IQ-scores. A significant effect of chorion type was found: the MC twins resembled each other more than the DC-MZ twins on the subscales Arithmetic and Vocabulary. The effect accounts for respectively 14% and 10% of the total variance.

Adult↗
PubMed2001

A quantitative genetic study of cephalometric variables in twins.

This study aimed at determining the relative genetic and environmental impact on a number of well-known cephalometric variables in twins. In order to find a clue in the heritability pattern of some dentofacial characteristics and on the expected limits of the therapeutic impact on the dentofacial subparts they are representing. Cephalograms were collected from 33 monozygotic and 46 dizygotic twins, who did not undergo any orthodontic treatment. Nineteen linear and four angular variables were selected all representing a different definite subpart of the dentofacial complex. The reproducibility of the measurement of most of the linear variables was very high. A genetic analysis using model fitting and path analysis was carried out. First, data were checked on the fulfilment of the conditions for genetic analysis in twins reared together. The results show that the genetic determination is significantly higher for vertical (72%) than for horizontal (61%) variables. As far as the genetic component is concerned, all variables selected seem to be inherited by additive genes, except for mandibular body length, which was determined by dominant alleles. Sex differences in genetic determination were found for the anterior face height, showing a significantly higher genetic component for boys (91%) than for girls (68%). For the angular measurements, no genetic influence was found: only environmental influences common to both members of each pair could be demonstrated.

Journal Article↗
PubMed2001

Birth weight and body composition in young adult men--a prospective twin study.

OBJECTIVES: To evaluate the association between birth weight and adult body composition in twins, controlling for maternal and genetic influences. DESIGN: Twins were randomly selected from the East Flanders Prospective Twin Survey, a population-based historic twin cohort. SUBJECTS: Male members of 229 twin pairs between 18 and 34 y of age who participated in the Prenatal Programming Twin Study. MEASUREMENTS: Adult body mass, height, BMI, lean body mass, sum of skinfolds and waist-to-hip-ratio. Lean body mass, sum of skinfolds and waist-to-hip-ratio were also adjusted for body mass. Intra-pair difference in adult anthropometric measures between the heaviest and the lightest twin at birth. RESULTS: Per kg increase in birth weight, body mass (4.2 kg), height (3.3 cm), lean body mass (3.1 kg) and to a lesser extent BMI (0.49 kg/m(2)) increased, whereas waist-to-hip-ratio (-1.4%) and sum of skinfolds (-0.11 s.d.) decreased, when adjusted for body mass. In a pair-wise analysis, the heavier twin at birth was taller and heavier as an adult, but, when adjusted for body mass, he had a lower waist-to-hip-ratio, less subcutaneous fat, and more lean body mass, compared to his lighter sib. Intra-pair difference in body composition was associated with intra-pair birth weight difference in monozygotic and dizygotic twins. CONCLUSIONS: An adverse intra-uterine environment, as measured by birth weight, is associated with more subcutaneous and abdominal fat and less lean body mass in adulthood. This association is independent of maternal and genetic influences. However, we cannot exclude the existence of genes that act on both birth weight and adult body composition.

Adolescent↗
PubMed2001

Birthweight in liveborn twins: the influence of the umbilical cord insertion and fusion of placentas.

OBJECTIVE: To assess the relation of umbilical cord insertion and fusion of placentas with birthweight in monozygotic monochorionic, monozygotic dichorionic, and dizygotic twins. DESIGN: A prospective population study. POPULATION: 4529 liveborn twin pairs whose birthweight was recorded, placentas were examined, and site of umbilical cord insertion was determined after delivery. RESULTS: Infants with a peripheral cord insertion weighed 150g less (P < 0.001) than infants with a central cord insertion. Dizygotic infants had a significantly (P < 0.001) higher incidence of central cord insertion (82%) than monozygotic dichorionic (65%) and monozygotic monochorionic (53%) infants. Monozygotic dichorionic infants with fused placentas and a peripheral cord insertion weighed on average 300g less (P < 0.01) than infants with separate placentas and a central cord insertion. In dizygotic infants, fusion of the placentas did not affect birthweight. CONCLUSIONS: Umbilical cord insertion is associated with birthweight in all types of twins. Fusion of the placentas only affects the birthweight of monozygotic dichorionic, not that of dizygotic infants. This might be due to the greater proximity of implantation of monozygotic dichorionic twins. Dizygotic twins weighed more than monozygotic twins only when placentas were fused and cord insertion was peripheral. Hence, the difference between the mean birthweights of dizygotic, monozygotic dichorionic, and monozygotic monochorionic infants may originate from the least favourable antenatal situation, namely fused placentas with a peripheral cord insertion, which occurs most frequently in monozygotic twins.

Analysis of Variance↗
PubMed2001

Twins, chorionicity and zygosity.

Accurate determination of zygosity and chorionicity is essential in all multiple maternities. The parents and the multiples themselves ask it. It is of medical importance and now considered as a prerequisite in several domains of twin research, especially when perinatal data are analysed. It helps the multiples and their parents and teachers to ascertain identity. The methods are briefly described and a plea is made to obstetricians and paediatricians to use them systematically at the time of birth.

Amnion↗
PubMed2001

The influence of zygosity and chorion type on fat distribution in young adult twins consequences for twin studies.

An adverse intra-uterine environment has been associated with abdominal fat distribution in singletons. Twins often have a low birth weight and a short gestation. Therefore, they may have an increased risk to develop abdominal obesity. Furthermore, monozygotic monochorionic twins (MZ MC) have a larger intra-pair birth weight difference compared to monozygotic dichorionic twins (MZ DC). If adult anthropometry is programmed in utero, this may affect the intra-pair correlations in adulthood and, consequently, also the results from the classic twin method to estimate genetic and environmental influences. In the present study, we compared the absolute values, the intra-pair differences, and the intra-pair correlations of body mass, height, BMI, and abdominal fat distribution of 424 MZ MC, MZ DC and dizygotic (DZ) twin pairs (aged 18-34 yrs). DZ, MZ DC and MZ MC twins did not differ for most anthropometric characteristics. Only MZ women tended (p = 0.03) to accumulate more abdominal fat compared to DZ twins. Overall, the contribution of zygosity and chorion type to adult anthropometry was rather low (< or = 1.7%). Although the intra-pair birth weight difference of MZ MC pairs (10.5% in men, 12.3% in women) was significantly larger compared to that of MZ DC pairs (6.9% and 9.2% resp.), the intra-pair differences in adult anthropometry were similar for both MZ twin types. Also the intra-pair correlations of MZ MC and MZ DC pairs were strikingly alike, suggesting no significant influence of the prenatal environment on adult concordance. In conclusion, the substantial difference in the prenatal environment of MZ MC and MZ DC twins did not result in a difference in intra-pair concordance of adult anthropometry and fat distribution. Therefore, we suggest that the chorion type of MZ twins does not bias the twin design and the estimation of the genetic contribution to adult anthropometry.

Adipose Tissue↗
PubMed2001

Hypodontia and tooth formation in groups of children with cleft, siblings without cleft, and nonrelated controls.

OBJECTIVE: To compare the occurrence of hypodontia, dental age, and asymmetric dental development in children with cleft with their siblings and a nonsibling control group. SUBJECTS: The sample consisted of 54 children with cleft (aged 4.2 to 13.1 years), who had at least one sibling available for an orthopantomogram, 63 siblings without cleft (aged 4 to 14.9 years) and 250 controls without cleft (aged between 4 and 14.9 years). METHOD: Hypodontia, dental age, and asymmetric dental development were assessed on panoramic radiographs of the children with cleft, the siblings without cleft, and the control children without cleft. RESULTS: Both the cleft (p <.001) and the sibling group (p <.05) showed a significantly higher frequency of hypodontia and a significantly higher occurrence (cleft p <.01 and sibling group p <.001) of asymmetric dental development, compared with the control group. Only a small, but insignificant, delay in dental development could be found in the cleft and the sibling group. CONCLUSIONS; The cleft subjects with siblings showed a significantly higher occurrence of hypodontia and asymmetric dental development than the noncleft control group. This may suggest a genetic component for the occurrence of hypodontia and asymmetric dental development.

Adolescent↗
PubMed1998

Validation of a telephone zygosity questionnaire in twins of known zygosity.

The aim of this study was to validate a zygosity questionnaire that can be administered over the telephone. Mothers of same-sexed twins of known zygosity and chronicity between 2 and 31 years of age were interviewed on a nine-item questionnaire. From the answers one unweighted and four weighted indices were computed. As single questions, the mother's opinion and the "two peas in a pod" question differentiated best between monozygotic and dizygotic twins. One independent well-trained observer assessed the zygosity based on the questionnaire and made the correct diagnosis in 96% of the cases. A weighted index of eight similarity questions yielded an accuracy of 98%. This study shows that the zygosity of same-sexed twins more than 2 years old and without gross physical malformation can reliably be determined by a telephone questionnaire with a high accuracy.

Adolescent↗
PubMed1998

Univariate and multivariate genetic analysis of subcutaneous fatness and fat distribution in early adolescence.

Univariate and multivariate analyses of the genetic and environmental contributions to variance in adipose tissue and adipose tissue distribution were carried out in early adolescents. Stature, weight, body mass index (BMI), and five subcutaneous skinfolds were measured at half-yearly intervals in 105 MZ and DZ twin pairs from 10 to 14 years. The most parsimonious model, which provided an adequate explanation for variation in the BMI, five skinfolds, and the T/E ratio, included additive genetic and specific environmental factors. Multivariate analyses of the genetic architecture of subcutaneous fat indicated a general skinfold genetic factor, an extremity skinfold genetic factor, and skinfold specific genetic factors. This implies that all skinfolds are under control of the same set of genes, that a different set of genes partly controls extremity skinfolds, and that other genes have a small skinfold specific impact. Environmental contributions included a general skinfold environmental factor and skinfold specific environmental factors. BMI is under control of the same set of genes as skinfolds and shows high genetic correlations with trunk skinfolds, which implies that nearly the same genes may influence trunk skinfolds and the BMI. All models were fairly consistent across the age range.

Adipose Tissue↗