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Journal of Oral Rehabilitation Sep 2020Sleep bruxism (SB) and awake bruxism (AB) have been considered different entities, although co-occurrence between them has been shown. While genetic factors have a...
BACKGROUND
Sleep bruxism (SB) and awake bruxism (AB) have been considered different entities, although co-occurrence between them has been shown. While genetic factors have a marked influence on phenotypic variance in liability to SB, this remains unclear for AB.
AIM
To examine the degree of co-occurrence of SB and AB, and whether they have common correlates and also twin similarity of SB and AB bruxism traits by zygosity and sex.
METHODS
A questionnaire was mailed to all twins born 1945-1957 in Finland in 2012 (n = 11 766). Age and sex adjusted logistic regression models were used. Twin similarity was assessed using polychoric correlations, and crosstwin-crosstrait correlations were computed.
RESULTS
The response rate was 72% (n = 8410). Any SB was reported by 14.8% and ≥ 3 nights weekly by 5.0%. Percentages for any AB were 18.4% and 6.3%, respectively. There was substantial co-occurrence (29.5%) between SB and AB, and several shared correlates were found. For SB, the polychoric intra-class correlation was 0.366 in monozygotic (MZ) and 0.200 in dizygotic (DZ) pairs, without gender difference. A twofold crosstwin-crosstrait correlation was observed in MZ twins compared to DZ twins.
CONCLUSIONS
The risk factor profiles of SB and AB were largely but not entirely similar. The higher correlation in MZ than in DZ pairs suggests the influence of genetic factors on both SB and AB. The higher crosstwin-crosstrait correlation in MZ than in DZ pairs suggests some degree of genetic influences shared by SB and AB.
Topics: Finland; Humans; Self Report; Twins, Dizygotic; Twins, Monozygotic; Wakefulness
PubMed: 32613647
DOI: 10.1111/joor.13042 -
Genes, Brain, and Behavior Feb 2022Visual search guides goal-directed action in humans and many other species, and it has been studied extensively in the past. Yet, no study has investigated the relative...
Visual search guides goal-directed action in humans and many other species, and it has been studied extensively in the past. Yet, no study has investigated the relative contributions of genes and environments to individual differences in visual search performance, or to which extent etiologies are shared with broader cognitive phenotypes. To address this gap, we studied visual search and general intelligence in 156 monozygotic (MZ) and 158 same-sex dizygotic (DZ) twin pairs. We found that different indexes of visual search performance (response latency and visual search efficiency) were moderately heritable. Phenotypic correlations between visual search and intelligence were small-to-moderate, and only a small proportion of the genetic variance in visual search was shared with genetic variance in intelligence. We discuss these findings in the context of the "generalist genes hypothesis" stating that different cognitive functions have a common genetic basis.
Topics: Humans; Intelligence; Phenotype; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35044053
DOI: 10.1111/gbb.12779 -
The Journal of Bone and Joint Surgery.... Apr 2019The literature is certain regarding the multifactorial etiology of rotator cuff degeneration. However, it remains unclear if rotator cuff degeneration exclusively...
BACKGROUND
The literature is certain regarding the multifactorial etiology of rotator cuff degeneration. However, it remains unclear if rotator cuff degeneration exclusively depends on intrinsic and extrinsic factors or if it is also genetically determined. We compared the health status of cuff tendons, evaluated with a magnetic resonance imaging (MRI) study, between elderly monozygotic and dizygotic twins with the aim of separating the contributions of genetics from shared and unique environments.
METHODS
The rotator cuff tendon status was assessed using the Sugaya classification by MRI. Heritability, defined as the proportion of total variance of a specific characteristic in a particular population due to a genetic cause, was calculated as twice the difference between the intraclass correlation coefficients for monozygotic and dizygotic pairs. The influence of shared environment, which contributes to twin and sibling similarity, was calculated as the difference between the monozygotic correlation coefficient and the heritability index.
RESULTS
We identified 33 pairs of elderly twins: 17 monozygotic pairs and 16 dizygotic pairs, with a mean age (and standard deviation) of 64.62 ± 3.32 years. The polychoric correlation was 0.62 in monozygotic twins and 0.53 in dizygotic twins. The calculated heritability index was 0.18 (18%), and the contribution was 0.44 (44%) for the shared environment and 0.38 (38%) for the unique environment.
CONCLUSIONS
The role of genetics in rotator cuff degeneration is quantified by our study on elderly monozygotic and dizygotic twins; however, it is only partial with respect to the contribution of shared and unique environments.
Topics: Aged; Diseases in Twins; Employment; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Risk Factors; Rotator Cuff Tear Arthropathy; Twins, Dizygotic; Twins, Monozygotic
PubMed: 30946193
DOI: 10.2106/JBJS.18.00761 -
The Journal of Physiology Jun 2022We studied monozygotic (MZ) and dizygotic (DZ) twin pairs following resistance (RES) and endurance (END) training to assess genetic and environmental contributions to... (Randomized Controlled Trial)
Randomized Controlled Trial
We studied monozygotic (MZ) and dizygotic (DZ) twin pairs following resistance (RES) and endurance (END) training to assess genetic and environmental contributions to cerebrovascular function. Cerebrovascular function (rest, autoregulation, hypercapnia, exercise) was assessed in 86 healthy same-sex MZ (30 pairs) and DZ (13 pairs) twins, who underwent 3 months of END and RES. Carbon dioxide ( ), mean arterial pressure (MAP) and middle cerebral artery velocity (MCAv) were measured and MCAv resistance (MCA ) was calculated. Resting MCAv reduced by -2.8 cm/s following RES (P = 0.024), with no change following END (-0.3 cm/s, P = 0.758). Change in MCA following RES was +0.11 mmHg/cm/s (P < 0.001), which was significantly greater than END (+0.02 mmHg/cm/s, P = 0.030). MAP also increased following RES (+4 mmHg, P = 0.010), but not END (+1 mmHg, P = 0.518). No changes were apparent in . At rest, positive response rates following RES ranged from 27 to 71% and from 40 to 64% following END. Intraclass correlations between twins were moderate for most variables at baseline. In response to training, only MZ pairs were significantly correlated for a change in MCAv (P = 0.005) and low frequency phase (P = 0.047) following RES.This study is the first to compare cerebrovascular function following RES and END in MZ and DZ twins. Most individuals who did not respond to one modality were able to respond by switching modality, and baseline heritability estimates were higher than training response. Exercise professionals should therefore consider modality and environmental factors when optimising interventions. KEY POINTS: Characterising individual responses to resistance and endurance exercise training can inform optimal strategies for exercise prescription. This study utilised monozygotic and dizygotic twins in a randomised cross-over study to determine individual responsiveness to different modalities of exercise training. The influence of environment vs. genetics on cerebrovascular responses to training was determined. It is apparent that individuals respond differently to distinct exercise stimuli and that switching modality may be a beneficial way to obtain positive responses in cerebrovascular function. This study has implications for improving individualised exercise prescription to maintain or improve cerebrovascular structure and function.
Topics: Cerebrovascular Circulation; Cross-Over Studies; Endurance Training; Exercise; Humans; Middle Cerebral Artery; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35474455
DOI: 10.1113/JP282998 -
Placenta Mar 2023Villitis of unknown etiology (VUE), chronic chorioamnionitis (CC), chronic deciduitis (CD) and chronic histiocytic intervillositis (CHI) are most likely the result of a...
Villitis of unknown etiology, chronic deciduitis, chronic chorioamnionitis and chronic histiocytic intervillositis in monozygotic and dizygotic twin pregnancies. A retrospective analysis of 16 cases.
INTRODUCTION
Villitis of unknown etiology (VUE), chronic chorioamnionitis (CC), chronic deciduitis (CD) and chronic histiocytic intervillositis (CHI) are most likely the result of a pathologic immune reaction caused by maternal anti-fetal rejection. We analyzed placentas of twin pregnancies with manifestation of these lesions in monozygotic and dizygotic instances.
METHODS
Twin pregnancies from our archive with at least one chronic inflammatory lesion were selected for further analysis and assessed concerning zygosity (gender, chorionicity, short tandem repeat (STR)-analysis).
RESULTS
The cohort comprised sixteen twin placentas, monozygotic in five cases and dizygotic in 11 cases, respectively. VUE (n = 4), CC (n = 1) and CHI (n = 3) manifested concordantly in both placentas of the monozygotic pregnancies and affected discordantly one of the twin placentas in the dizygotic instances. CD (n = 10) manifested concordantly in two and discordantly in one of the monozygotic placentas, and concordantly in three and discordantly in four of the dizygotic instances. Intrauterine fetal demise (n = 3), preterm birth (n = 9) and low birth weight (n = 2) were recognized. Discordant fetal growth in live born children was recognized in two dizygotic cases with discordant manifestation of VUE and CHI.
DISCUSSION
The concordant manifestation of VUE, CC and CHI in monozygotic and the discordant pattern of inflammation in dizygotic pregnancies points to pathologic immune mechanisms against genetically determined fetal antigens being essential for the development of these entities. The heterogenous manifestation of CD could be a hint for diverse fetal or maternal etiologic factors that may contribute to this lesion.
Topics: Pregnancy; Female; Child; Infant, Newborn; Humans; Chorioamnionitis; Retrospective Studies; Pregnancy, Twin; Premature Birth; Placenta; Placenta Diseases; Pregnancy Complications; Twins, Monozygotic; Twins, Dizygotic
PubMed: 36791493
DOI: 10.1016/j.placenta.2023.02.002 -
Journal of Epidemiology Jan 2019Inherited factors and maternal behaviors are thought to play an important role in the etiology of several congenital malformations. Twin studies can offer additional...
BACKGROUND
Inherited factors and maternal behaviors are thought to play an important role in the etiology of several congenital malformations. Twin studies can offer additional evidence regarding the contribution of genetic and lifestyle factors to common birth anomalies, but few large-scale studies have been reported.
METHODS
We included data from twins (20,803 pairs) from the population-based California Twin Program. We compared concordance in monozygotic (MZ) to dizygotic (DZ) twins for the following birth anomalies: clubfoot, oral cleft, spina bifida, muscular dystrophy, deafness, cerebral palsy, strabismus, and congenital heart defects. Each birth anomaly was also examined for the associations with birth characteristics (birthweight and birth order) and parental exposures (age, smoking, and parental education).
RESULTS
The overall prevalence of any selected birth anomaly in California twins was 38 per 1,000 persons, with a slightly decreasing trend from 1957-1982. For pairwise concordance in 6,752 MZ and 7,326 like-sex DZ twin pairs, high MZ:DZ concordance ratios were observed for clubfoot (CR 5.91; P = 0.043) and strabismus (CR 2.52; P = 0.001). Among the total 20,803 pairs, parental smoking was significantly associated with risk of spina bifida (OR 3.48; 95% CI, 1.48-8.18) and strabismus (OR 1.61; 95% CI, 1.28-2.03). A significant quadratic trend of increasing risk for clubfoot, spina bifida, and strabismus was found when examining whether father smoked, mother smoked, or both parents smoked relative to non-smoking parents (P = 0.029, 0.026, and 0.0005, respectively).
CONCLUSIONS
Our results provide evidence for a multifactorial etiology underlying selected birth anomalies. Further research is needed to understand the biological mechanisms.
Topics: California; Congenital Abnormalities; Diseases in Twins; Female; Gene-Environment Interaction; Humans; Infant, Newborn; Male; Prevalence; Registries; Smoking; Twins, Dizygotic; Twins, Monozygotic
PubMed: 30270263
DOI: 10.2188/jea.JE20170159 -
Journal of Child Psychology and... Mar 2022Difficulties initiating and maintaining sleep (DIMS) are frequent features of autism, yet little is known about why these conditions co-occur. One possibility is that...
BACKGROUND
Difficulties initiating and maintaining sleep (DIMS) are frequent features of autism, yet little is known about why these conditions co-occur. One possibility is that they share etiological factors, yet this hypothesis remains to be tested using quantitative genetic designs. We thus investigated etiological links between autism and DIMS using familial co-aggregation and twin methods.
METHODS
Twins, siblings, half-siblings, and cousins of 50,097 individuals with autism were identified from Swedish population registries. Their risk of DIMS, defined through diagnoses of insomnia and/or melatonin prescriptions, was then estimated. Twin analyses conducted on 15,279 child and adolescent twin pairs investigated etiological links between DIMS and ASD.
RESULTS
22.8% of autistic individuals had DIMS. Monozygotic co-twins of individuals with autism were most at risk of DIMS compared to the reference group (OR = 6.6 [2.5-17.4]), followed by dizygotic co-twins (OR = 2.6 [1.5-4.5]) and full siblings (OR = 2.5 [2.4-2.6]). Half-siblings and cousins of individuals with autism were least likely to have DIMS relative to the reference group (OR range = 1.3-1.5). Twin analyses estimated a correlation of 0.57 (0.53-0.61) between autism and DIMS, with a genetic correlation of 0.62 (0.60-0.68). These overlapping genetic factors explained 94% of the covariance between these conditions. Autistic traits also showed genetic overlap with DIMS.
CONCLUSIONS
Our results suggest that shared genetic mechanisms underlie autism and DIMS, which may lead them to co-occur. Untangling the etiological overlap between these conditions has potential to assist in understanding the etiology of each condition, as well as their associated outcomes.
Topics: Adolescent; Autistic Disorder; Child; Diseases in Twins; Humans; Sleep; Twins, Dizygotic; Twins, Monozygotic
PubMed: 34213012
DOI: 10.1111/jcpp.13473 -
Twin Research and Human Genetics : the... Aug 2020The aim of the study was to examine the Family and School Psychosocial Environment (FSPE) questionnaire in relation to a possible genotype-environment correlation and...
The aim of the study was to examine the Family and School Psychosocial Environment (FSPE) questionnaire in relation to a possible genotype-environment correlation and genetic mediation between the FSPE variables and personality variables, assessed by the Junior Eysenck Personality Questionnaire. A sample of 506 Swedish children aged 10-20 years from 253 families were recruited via the Swedish state population and address register and SchoolList.Eu. The children were divided into 253 pairs: 46 monozygotic twin pairs, 42 dizygotic twin pairs, 140 pairs of full siblings and 25 pairs of half-siblings. The behavioral genetic analysis showed that both FSPE factors, Warmth and Conflicts, may be partly influenced by genetic factors (suggesting genotype-environment correlation) and that nonadditive genetic factors may mediate the relationship between FSPE factors and psychoticism/antisocial personality (P). An indication of a special shared monozygotic twin environment was found for P and Lie/social desirability, but based on prior research findings this factor may have a minor influence on P and L. P and L were negatively correlated, and the relationship seems to be partly mediated by nonadditive genetic factors. Nonshared environment and measurement errors seem to be the most influential mediating factors, but none of the cross-twin cross-dimension correlations suggest a common shared environmental mediating factor.
Topics: Adolescent; Child; Gene-Environment Interaction; Genotype; Humans; Personality; Sweden; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 32772950
DOI: 10.1017/thg.2020.63 -
Journal of Speech, Language, and... Oct 2020Purpose This review article summarizes a program of longitudinal investigation of twins' language acquisition with a focus on causal pathways for specific language... (Review)
Review
Purpose This review article summarizes a program of longitudinal investigation of twins' language acquisition with a focus on causal pathways for specific language impairment (SLI) and nonspecific language impairment in children at 4 and 6 years with known history at 2 years. Method The context of the overview is established by legacy scientific papers in genetics, language, and SLI. Five recent studies of twins are summarized, from 2 to 16 years of age, with a longitudinal perspective of heritability over multiple speech, language, and cognitive phenotypes. Results Replicated moderate-to-high heritability is reported across ages, phenotypes, full population estimates, and estimates for clinical groups. Key outcomes are documentation of a twinning effect of risk for late language acquisition in twins that persists through 6 years of age, greater for monozygotic than dizygotic twins (although zygosity effects disappear at 6 years); heritability is greater for grammar and morphosyntax than other linguistic dimensions, from age 2 years through age 16 years, replicated within twin samples at subsequent age levels and across twin samples at age 16 years. Conclusion There is consistent support for legacy models of genetic influences on language acquisition, updated with a more precise growth signaling disruption model supported by twin data, as well as singleton data of children with SLI and nonspecific language impairment. Presentation Video https://doi.org/10.23641/asha.13063727.
Topics: Adolescent; Child; Child, Preschool; Humans; Language Development; Specific Language Disorder; Speech; Twins, Dizygotic; Twins, Monozygotic
PubMed: 33064600
DOI: 10.1044/2020_JSLHR-20-00169 -
Alzheimer's & Dementia : the Journal of... Mar 2024Dementia predicts increased mortality. We used case-control and co-twin control models to investigate genetic and shared environmental influences on this association.
INTRODUCTION
Dementia predicts increased mortality. We used case-control and co-twin control models to investigate genetic and shared environmental influences on this association.
METHODS
Case-control design, including 987 twins with dementia and 2938 age- and sex-matched controls in the Swedish Twin Registry. Co-twin control design, including 90 monozygotic (MZ) and 288 dizygotic (DZ) twin pairs discordant for dementia. To test for genetic and environmental confounding, differences were examined in mortality risk between twins with dementia and their matched or co-twin controls.
RESULTS
Twins with dementia showed greater mortality risk than age- and sex-matched controls (HR = 2.02 [1.86, 2.18]). Mortality risk is significantly elevated but attenuated substantially in discordant twin pairs, for example, comparing MZ twins with dementia to their co-twin controls (HR = 1.48 [1.08, 2.04]).
DISCUSSION
Findings suggest that genetic factors partially confound the association between dementia and mortality and provide an alternative hypothesis to increased mortality due to dementia itself. Highlights We studied dementia and mortality in twin pairs discordant for dementia. People without dementia outlived people with dementia. Identical twins with dementia and their co-twin controls had similar survival time. Findings suggest genotype may explain the link between dementia and mortality.
Topics: Aged; Humans; Dementia; Genotype; Sweden; Twins, Dizygotic; Twins, Monozygotic; Male; Female
PubMed: 38078564
DOI: 10.1002/alz.13553