-
Sports Medicine - Open Dec 2017There is evidence for considerable heterogeneity in the responsiveness to regular physical activity (PA) which might reflect the influence of genetic factors. The aim of... (Review)
Review
BACKGROUND
There is evidence for considerable heterogeneity in the responsiveness to regular physical activity (PA) which might reflect the influence of genetic factors. The aim of this systematic review was to assess whether the response to a PA intervention for measures of body composition and cardiorespiratory fitness is (i) correlated within twin pairs and/or families and (ii) more correlated in monozygotic twins (MZ) compared to dizygotic twins (DZ), which would be consistent with genetic effects.
METHODS
We performed electronic database searches, combining key words relating to "physical activity" and "genetics", in MEDLINE, CINAHL, EMBASE, SPORTS Discuss, AMED, PsycINFO, WEB OF SCIENCE, and SCOPUS from the earliest records to March 2016. Twin and family studies were included if they assessed body composition and/or cardiorespiratory fitness following a PA intervention, and provided a heritability estimate, maximal heritability estimate, or within MZ twin pair correlation (r). Data on heritability (twin studies), maximal heritability (family studies), and the r were extracted from included studies, although heritability estimates were not reported as small sample sizes made them uninformative.
RESULTS
After screening 224 full texts, nine twin and five family studies were included in this review. The pooled r in response to PA was significant for body mass index (r = 0.69, n = 58), fat mass (r = 0.58, n = 48), body fat percentage (r = 0.55, n = 72), waist circumference (r = 0.50, n = 27), and VOmax (r = 0.39, n = 48), where "n" represents the total number of twin pairs from all studies. Maximal heritability estimates ranged from 0-21% for measures of body composition, and 22-57% for cardiorespiratory fitness. Twin studies differed in sample age, baseline values, and PA intervention, although the exclusion of any one study did not affect the results.
CONCLUSIONS
Shared familial factors, including genetics, are likely to be a significant contributor to the response of body composition and cardiorespiratory fitness following PA. Genetic factors may explain individual variation in the response to PA.
TRIAL REGISTRATIONS
PROSPERO Registration No CRD42015020056 .
PubMed: 28074345
DOI: 10.1186/s40798-016-0073-9 -
Human Reproduction Update Jul 2018The incidence of monozygotic twins (MZT) after ART appears to be higher than the incidence after spontaneous conceptions contradicting the aim of ART to avoid multiple... (Meta-Analysis)
Meta-Analysis
BACKGROUND
The incidence of monozygotic twins (MZT) after ART appears to be higher than the incidence after spontaneous conceptions contradicting the aim of ART to avoid multiple pregnancies because of the associated risks.
OBJECTIVE AND RATIONALE
The aim was to study the frequency of MZT after IVF and ICSI and how it is influenced by the day of embryo transfer, maternal age, zona pellucida manipulation, controlled ovarian stimulation, stimulation protocol, culture media and embryo quality.
SEARCH METHODS
Original studies and reviews were identified by searching the PubMed, Embase and Cochrane databases up to March 2017. The inclusion criterion was publications focusing on the five study questions related to MZT in our study. The exclusion criteria were articles that did not include blastocyst transfer, were on non-humans, were not published in peer-reviewed journals, and were based only on case studies. All of the articles were categorized according to the Oxford Centre for Evidence-based Medicine's 'Levels of Evidence', and quality and risk of bias assessment was performed with 'The Cochrane Collaboration's Risk of Bias Tools'. A meta-analysis was performed to study the impact of the day of embryo transfer on the MZT rate.
OUTCOMES
The literature search resulted in a total of 42 articles, including 38 original studies, for analysis. The included original studies reported a MZT rate with blastocyst transfer from zero to 13.2%. Our meta-analysis found a higher frequency of MZT after blastocyst transfer compared with cleavage-stage embryos transfer: odds ratio = 2.18, 95% CI: 1.93-2.48 (fixed effect meta-analysis). A younger maternal age may increase the MZT rate, and recent studies regarding the use of zona pellucida manipulating techniques have disagreed with the previous suspicion of a higher MZT rate after the use of these methods. The extended culture to-blastocyst stage is a potential risk factor for MZT, but it is uncertain whether this phenomenon is due to the extended time, culture media or greater likelihood of younger oocytes to reach the blastocyst stage. An increased frequency of MZT following the GnRH-agonist suppression protocol has been suggested, as well as a decreased frequency of MZT with high gonadotrophin doses, which could reflect an age-related effect. Only limited literature has focused on the role of embryo morphology in the MZT rate, therefore, this issue remains unresolved.
WIDER IMPLICATIONS
We found blastocyst transfer to be a risk factor for MZT. Hence, the results of this meta-analysis may weaken the previously proposed view that greater experience with blastocyst transfer and improved culture media could decrease the high rate of MZT after blastocyst transfer. To minimize the rate of MZT and the associated complications, the mechanisms underlying blastocyst transfer and MZT pregnancy must be elucidated.
Topics: Embryo Transfer; Female; Humans; Incidence; Infant, Newborn; Pregnancy; Pregnancy Rate; Pregnancy, Twin; Reproductive Techniques, Assisted; Risk Factors; Twinning, Monozygotic; Twins, Monozygotic
PubMed: 29538675
DOI: 10.1093/humupd/dmy006 -
EFORT Open Reviews May 2022Idiopathic scoliosis is the most common spinal deformity and affects 1-3% of children and adolescents. Idiopathic scoliosis may run in families and the purpose of this... (Review)
Review
PURPOSE
Idiopathic scoliosis is the most common spinal deformity and affects 1-3% of children and adolescents. Idiopathic scoliosis may run in families and the purpose of this systematic review was to describe the degree of heritability.
METHODS
We searched Medline, Web of Science and EMBASE for family and twin studies reporting heritability estimates for idiopathic scoliosis, or studies from which heritability estimates could be calculated. Reference lists were screened for additional papers. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol was registered at PROSPERO (registration number: CRD42022307329).
RESULTS
The literature search identified 1134 reports. After full-text screening, nine eligible reports were included for data extraction. Seven were twin studies containing between 5 and 526 pairs, and two were family studies with 1149 and 2732 individuals, respectively. Quality was 'good' in four studies and 'fair' in five studies. In general, studies with radiograph-confirmed diagnosis reported higher heritability estimates than studies with self-reported diagnosis. Population-based twin studies reported lower heritability estimates than clinic-based twin studies. Family-based studies reported higher heritability estimates than twin studies. Pairwise concordance for scoliosis ranged from 0.11 to 1.00 in monozygotic twins and from 0 to 1.0 in dizygotic twins. A meta-analysis of three studies resulted in a narrow sense heritability estimate of 0.57 (95% CI: 0.29-0.86).
CONCLUSION
Twin and family studies indicate a hereditary component in idiopathic scoliosis, but study heterogeneity is large, and the degree of the heritability is uncertain. Nevertheless, known genetic variants associated with idiopathic scoliosis can still only explain a minor part of heritability.
PubMed: 35638601
DOI: 10.1530/EOR-22-0026 -
BJOG : An International Journal of... Sep 2001To review the experience of the University of Toronto Perinatal Complex, Ontario, Canada concerning antenatally diagnosed monoamniotic twin pregnancies; and to compare... (Review)
Review
OBJECTIVES
To review the experience of the University of Toronto Perinatal Complex, Ontario, Canada concerning antenatally diagnosed monoamniotic twin pregnancies; and to compare our results with cases reported in the literature with respect to antenatal surveillance and perinatal outcome.
METHODS
A retrospective chart review of all twin gestations from 1993 to April 2000 was performed. A systematic review of the literature, 1966 to April 2000, of perinatal outcome in monoamniotic twin pregnancies was undertaken.
SETTING
All monoamniotic twin gestations at the University of Toronto.
RESULTS
Case-series: 25 prenatally diagnosed monoamniotic twin pregnancies were identified. Seven pregnancies were affected by fetal anomalies. One fetus died at 29 weeks. Neonatal complications occurred below 33 weeks of gestational age and were related to immaturity. Systematic review of the literature: 49 studies met our selection criteria and reported 88 cases diagnosed antenatally. Fourteen pregnancies were affected by major congenital anomalies. Twenty fetuses died after 24 weeks of gestation. Neonatal complications varied widely in severity and depended on gestational age at birth. The risk of intrauterine fetal death was 10% at the University of Toronto and 12% in the review of the literature.
DISCUSSION
Our experience, the largest so far, suggests that regular fetal surveillance and appropriate steroid administration leads to a good perinatal outcome. The risk of fetal death (10%-12%) is lower than the previously quoted risk of 30%-70%. A careful review of obstetric interventions and further work examining outpatient surveillance of monoamniotic twin pregnancies are needed. The best treatment of monoamniotic twin pregnancies can only be determined by randomised trials.
Topics: Adolescent; Adult; Female; Fetal Death; Gestational Age; Humans; Pregnancy; Pregnancy Outcome; Pregnancy, Multiple; Prenatal Care; Prenatal Diagnosis; Retrospective Studies; Twins, Monozygotic
PubMed: 11563462
DOI: 10.1111/j.1471-0528.2001.00216.x -
Human Reproduction Update 2009It is estimated that there is at least a 2-fold rise in the incidence of monozygotic twinning after assisted reproductive technology compared with natural conception.... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
It is estimated that there is at least a 2-fold rise in the incidence of monozygotic twinning after assisted reproductive technology compared with natural conception. This can result in adverse pregnancy outcomes.
METHODS
We searched MEDLINE, EMBASE and SCISEARCH for studies that estimated the risk of monozygotic twinning and its association with any particular assisted reproductive technique. Monozygotic twinning was defined by ultrasound or Weinberg criteria. A meta-analysis of the proportion of monozygotic twins was performed using both fixed and random effects models.
RESULTS
The search revealed 37 publications reporting on the incidence of monozygotic twins after assisted reproductive techniques. Twenty-seven studies met the inclusion criteria and were included in the meta-analysis. The summary incidence of monozygotic twins after assisted conception was 0.9% (0.8-0.9%). The incidence of monozygotic twins in natural conception is 0.4%. Blastocyst transfer and intracytoplasmic sperm injection are associated with 4.25 and 2.25 times higher risk of monozygotic twins.
CONCLUSIONS
The risk of monozygotic twins in assisted conception is 2.25 times higher than the natural conceptions. Larger studies reporting on monozygotic twinning following single-embryo transfer or after post-natal confirmation of zygosity with DNA analysis are warranted before definitive conclusions can be drawn and guidelines produced. In order to provide adequate pre-conceptional counselling, it is important to monitor the incidence of monozygotic twins in both natural and assisted conceptions. We suggest building a national multiple pregnancy database based on accurate diagnosis of zygosity.
Topics: Embryonic Development; Female; Humans; Reproductive Techniques, Assisted; Risk Assessment; Twinning, Monozygotic
PubMed: 18927071
DOI: 10.1093/humupd/dmn045 -
European Journal of Obstetrics,... Jul 2022Determine the impact of indication for selective reduction (SR) on co-twin survival in monochorionic gestations undergoing radiofrequency ablation (RFA) or bipolar cord... (Meta-Analysis)
Meta-Analysis Review
Co-twin survival after selective fetal reduction in complicated multiple gestations: A systematic review and meta-analysis of survival rate according to indication for intervention.
OBJECTIVE
Determine the impact of indication for selective reduction (SR) on co-twin survival in monochorionic gestations undergoing radiofrequency ablation (RFA) or bipolar cord coagulation (BCC).
METHODS
PubMed and Web of Science were systematically searched from inception of databases to April 2021. Frequency of indications was compared between post-intervention co-twin survival and demise groups undergoing SR. Random-effect model was used to pool mean differences or odds ratios (OR) and corresponding 95% confidence intervals (CIs). Heterogeneity was assessed using the I value.
RESULTS
Of 1060 studies assessed for eligibility, nine studies met criteria. A total of 666 pregnancies underwent RFA (n = 483 co-twin survival) and 235 pregnancies underwent BCC (n = 188 co-twin survival). Twin twin transfusion syndrome (TTTS), as an indication for RFA, was associated with decreased co-twin survival (OR 0.61, 95% CI 0.41, 0.90, P 0.01, I 0.0%). Other indications for RFA were not associated with significant difference in co-twin survival. With BCC, none of the indications were found to significantly influence the co-twin survival following intervention.
CONCLUSION
RFA was found to have lower co-twin survival when performed for TTTS. No other indications was associated with differences in co-twin survival. BCC was not associated with any differences in co-twin survival based on indication.
Topics: Female; Fetofetal Transfusion; Humans; Pregnancy; Pregnancy Complications; Pregnancy Outcome; Pregnancy Reduction, Multifetal; Pregnancy, Twin; Retrospective Studies; Survival Rate; Twins, Monozygotic
PubMed: 35661541
DOI: 10.1016/j.ejogrb.2022.05.028 -
Ultrasound in Obstetrics & Gynecology :... Mar 2020To explore the outcome of monochorionic monoamniotic (MCMA) twin pregnancies affected by twin-to-twin transfusion syndrome (TTTS). (Meta-Analysis)
Meta-Analysis
OBJECTIVES
To explore the outcome of monochorionic monoamniotic (MCMA) twin pregnancies affected by twin-to-twin transfusion syndrome (TTTS).
METHODS
MEDLINE and EMBASE databases were searched for studies reporting the outcome of MCMA twin pregnancies complicated by TTTS. The primary outcome was intrauterine death (IUD); secondary outcomes were miscarriage, single IUD, double IUD, neonatal death (NND), perinatal death (PND), survival of at least one twin, survival of both twins and preterm birth (PTB) before 32 weeks' gestation. Outcomes were assessed in MCMA twins affected by TTTS not undergoing intervention and in those treated with amniodrainage, laser therapy or cord occlusion. Subgroup analysis was performed including cases diagnosed before 24 weeks. Random-effects meta-analysis of proportions was used to analyze the data.
RESULTS
Fifteen cohort studies, including 888 MCMA twin pregnancies, of which 44 were affected by TTTS, were included in the review. There was no randomized trial comparing the different management options in MCMA twin pregnancies complicated by TTTS. In cases not undergoing intervention, miscarriage occurred in 11.0% of fetuses, while the incidence of IUD, NND and PND was 25.2%, 12.2% and 31.2%, respectively. PTB complicated 50.5% of these pregnancies. In cases treated by laser surgery, the incidence of miscarriage, IUD, NND and PND was 19.6%, 27.4%, 7.4% and 35.9%, respectively, and the incidence of PTB before 32 weeks' gestation was 64.9%. In cases treated with amniodrainage, the incidence of IUD, NND and PND was 31.3%, 13.5% and 45.7% respectively, and PTB complicated 76.2% of these pregnancies. Analysis of cases undergoing cord occlusion was affected by the very small number of included cases. Miscarriage occurred in 19.2%, while there was no case of IUD or NND of the surviving twin. PTB before 32 weeks occurred in 50.0% of these cases.
CONCLUSIONS
MCMA twin pregnancies complicated by TTTS are at high risk of perinatal mortality and PTB. Further studies are needed in order to elucidate the optimal type of prenatal treatment in these pregnancies. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.
Topics: Abortion, Spontaneous; Adult; Amnion; Chorion; Female; Fetal Death; Fetofetal Transfusion; Humans; Infant, Newborn; Perinatal Mortality; Pregnancy; Pregnancy Outcome; Pregnancy, Twin; Premature Birth; Twins, Monozygotic
PubMed: 31595578
DOI: 10.1002/uog.21889 -
The Spine Journal : Official Journal of... May 2015The relationships between obesity and low back pain (LBP) and lumbar disc degeneration (LDD) remain unclear. It is possible that familial factors, including genetics and... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND CONTEXT
The relationships between obesity and low back pain (LBP) and lumbar disc degeneration (LDD) remain unclear. It is possible that familial factors, including genetics and early environment, affect these relationships.
PURPOSE
To investigate the relationship between obesity-related measures (eg, weight, body mass index [BMI]) and LBP and LDD using twin studies, where the effect of genetics and early environment can be controlled.
STUDY DESIGN
A systematic review with meta-analysis.
METHODS
MEDLINE, CINAHL, Scopus, Web of Science, and EMBASE databases were searched from the earliest records to August 2014. All cross-sectional and longitudinal observational twin studies identified by the search strategy were considered for inclusion. Two investigators independently assessed the eligibility, conducted the quality assessment, and extracted the data. Metaanalyses (fixed or random effects, as appropriate) were used to pool studies' estimates of association.
RESULTS
In total, 11 articles met the inclusion criteria. Five studies were included in the LBP analysis and seven in the LDD analysis. For the LBP analysis, pooling of the five studies showed that the risk of having LBP for individuals with the highest levels of BMI or weight was almost twice that of people with a lower BMI (odds ratio [OR] 1.8; 95% confidence interval [CI] 1.6-2.0; I(2)=0%). A dose-response relationship was also identified. When genetics and the effects of a shared early environment were adjusted for using a within-pair twin case-control analysis, pooling of three studies showed a reduced but statistically positive association between obesity and prevalence of LBP (OR 1.5; 95% CI 1.1-2.1; I(2)=0%). However, the association was further diminished and not significant (OR 1.4; 95% CI 0.8-2.3; I(2)=0%) when pooling included two studies on monozygotic twin pairs only. Seven studies met the inclusion criteria for LDD. When familial factors were not controlled for, body weight was positively associated with LDD in all five cross-sectional studies. Only two cross-sectional studies investigated the relationship between obesity-related measures and LDD accounting for familial factors, and the results were conflicting. One longitudinal study in LBP and three longitudinal studies in LDD found no increase in risk in obese individuals, whether or not familial factors were controlled for.
CONCLUSIONS
Findings from this review suggest that genetics and early environment are possible mechanisms underlying the relationship between obesity and LBP; however, a direct causal link between these conditions appears to be weak. Further longitudinal studies using the twin design are needed to better understand the complex mechanisms underlying the associations between obesity, LBP, and LDD.
Topics: Case-Control Studies; Gene-Environment Interaction; Humans; Intervertebral Disc Degeneration; Low Back Pain; Lumbar Vertebrae; Obesity; Twins, Monozygotic
PubMed: 25661432
DOI: 10.1016/j.spinee.2015.02.001 -
Clinical Dysmorphology Oct 2012The VATER/VACTERL association is typically defined by the presence of at least three of the following congenital malformations: vertebral anomalies, anal atresia,... (Review)
Review
The VATER/VACTERL association is typically defined by the presence of at least three of the following congenital malformations: vertebral anomalies, anal atresia, cardiac malformations, tracheo-esophageal fistula, renal anomalies, and limb abnormalities. The identification of 14 twin pairs with an initial diagnosis of VATER/VACTERL association at our clinical centers led to the performance of a classical twin study. This involved a thorough evaluation of these 14 twin pairs and a further 55 twin pairs identified from a systematic review of the literature. The zygosity, concordance, and malformation status of all 69 twin pairs were evaluated. Twenty-four twin pairs fulfilled the criteria for inclusion in a comparison of the concordance rates between monozygous (MZ) and dizygous (DZ) twin pairs. The pairwise concordance rates were 15% [95% confidence interval (CI) 4-42%] for MZ and 18% (95% CI 5-48%) for DZ twin pairs (P=0.53). The probandwise concordance rates were 27% (95% CI 11-52%) for MZ and 31% (95% CI 13-58%) for DZ twin pairs (P=0.40). Although based on a limited number of twin pairs, the findings of the present study are consistent with the low number of familial cases reported to date, and suggest that the role of inherited genetic factors in the majority of VATER/VACTERL cases is limited.
Topics: Anus, Imperforate; Diseases in Twins; Esophagus; Heart Defects, Congenital; Humans; Radius; Spine; Trachea; Twins, Dizygotic; Twins, Monozygotic
PubMed: 22895008
DOI: 10.1097/MCD.0b013e328358243c -
Translational Psychiatry Jun 2023The first systematic review and meta-analysis of obsessive-compulsive disorder (OCD) genetic epidemiology was published approximately 20 years ago. Considering the... (Meta-Analysis)
Meta-Analysis
The first systematic review and meta-analysis of obsessive-compulsive disorder (OCD) genetic epidemiology was published approximately 20 years ago. Considering the relevance of all the studies published since 2001, the current study aimed to update the state-of-art knowledge on the field. All published data concerning the genetic epidemiology of OCD from the CENTRAL, MEDLINE, EMBASE, BVS, and OpenGrey databases were searched by two independent researchers until September 30, 2021. To be included, the articles had to fulfill the following criteria: OCD diagnosis provided by standardized and validated instruments; or medical records; inclusion of a control group for comparison and case-control, cohort or twin study designs. The analysis units were the first-degree relatives (FDRs) of OCD or control probands and the co-twins in twin pairs. The outcomes of interest were the familial recurrence rates of OCD and the correlations of OCS in monozygotic compared with dizygotic twins. Nineteen family, twenty-nine twin, and six population-based studies were included. The main findings were that OCD is a prevalent and highly familial disorder, especially among the relatives of children and adolescent probands, that OCD has a phenotypic heritability of around 50%; and that the higher OCS correlations between MZ twins were mainly due to additive genetic or to non-shared environmental components.
Topics: Adolescent; Child; Humans; Molecular Epidemiology; Twins, Dizygotic; Databases, Factual; Research Design
PubMed: 37380645
DOI: 10.1038/s41398-023-02433-2