Heritability of white matter in twins: A diffusion neuroimaging review.

Diffusion neuroimaging has emerged as an essential non-invasive technique to explore in vivo microstructural characteristics of white matter (WM), whose integrity allows complex behaviors and cognitive abilities. Studying the factors contributing to inter-individual variability in WM microstructure can provide valuable insight into structural and functional differences of brain among individuals. Genetic influence on this variation has been largely investigated in twin studies employing different measures derived from diffusion neuroimaging. In this context, we performed a comprehensive literature search across PubMed, Scopus and Web of Science of original twin studies focused on the heritability of WM. Overall, our results highlighted a consistent heritability of diffusion indices (i.e., fractional anisotropy, mean, axial and radial diffusivity), and network topology among twins. The genetic influence resulted prominent in frontal and occipital regions, in the limbic system, and in commissural fibers. To enhance the understanding of genetic influence on WM microstructure further studies in less heterogeneous experimental settings, encompassing all diffusion indices, are warranted.

Exploring the effects of family and life events on genetic and environmental architecture of schizotypal and hypomanic dimensions: Insights from a twin study.

BACKGROUND: Strategies of prevention for psychiatric disorders need a deep understanding of the aetiological factors involved in the psychopathological processes. Our twin study aims at disentangling the contributions of genes and environment to schizotypal and hypomanic dimensions, considering the role of stressful life events (LEs) and the quality of family relationships. METHODS: The Magical Ideation Scale (MIS) and Perceptual Aberration Scale (PAS) were used to assess positive schizotypy, while Hypomanic Personality Scale (HPS) and its sub-scales were used to investigate proneness to affective disorders. 268 twins (54.5 % female; aged 18.0 ± 6.68) were included. Participants filled out a questionnaire on LEs and their parents provided an evaluation of intra-family relationship (Relationship Quality Index, RQI). Classic univariate twin models for quantitative traits were fitted for scales, and the effects of covariates (LEs and RQI) were assessed. RESULTS: For MIS, HPS and its sub-scales, significant common and unique environmental effects were detected, with genetic factors affecting only HPS Social Vitality sub-scale. Unique environment was the only source of variance of PAS score. The number of recent LEs influenced MIS and PAS models, while RQI score affected MIS model. LIMITATIONS: The main limitation of the study is the small sample size, which reduces statistical power and may potentially lead to an underestimation of heritability. Additionally, the cross-sectional design limits the possibility to draw causal considerations. CONCLUSIONS: Findings provide preliminary evidence for a significant environmental role in modulating states of vulnerability. Moreover, the expression of positive schizotypy resulted influenced by recent stressors and intra-family relationships.

Connecting psychosocial and personality characteristics with mental health outcomes. An Italian co-twin control study.

Exposure to stressful life events is common, and it is linked to increased psychological issues. As most likely people respond to stressors depending on environmental and genetic factors, we assessed in a twin study the association of some personal characteristics such as resilience and self-perception with anxiety, depression and stress in the late Covid pandemic period, to verify the underlying genetic and shared familial components. With this design, the strength of the associations was compared between individual-level and intrapair-level analyses. From June 2020 to December 2021, the Italian Twin Registry conducted a three-wave longitudinal study among adult twins using validated questionnaires, and 1,763 adult twins participated in the study (mean age 46 years, 67 % females, 70 % monozygotic). A regression-based within-pair differences model was applied to control for genetic and shared environmental confounding. Results showed that anxiety was linked negatively with resilience, social support and perceived health, and positively with risk perception and hypochondria. Depression was associated negatively with resilience, social support and perceived health, and positively with financial concern and hypochondria. Stress was associated negatively with resilience and perceived health, and positively with financial concern, risk perception and hypochondria. These results suggest potential etiological effects of the above-mentioned risk factors. While our findings need to be confirmed by longitudinal studies, they propose potential etiological models for mental disorders, indicating that addressing in the clinical practice factors such as self-perception, personality traits (resilience), environmental resources (social support), and comorbid disorders (hypochondria) could have therapeutic benefits while treating certain common mental disorders.

An Italian Survey and Focus Groups on Fibromyalgia Impairment: Impact on Work and Possible Reasonable Accommodations.

Fibromyalgia symptoms affect the sufferers' working life; however, through reasonable accommodations in workplaces, they can continue to work satisfactorily. There are no Italian studies on factors that facilitate or hinder fibromyalgia-affected people's working life. Our objective was to explore, in a pre-pandemic setting, the quality of working life of fibromyalgia sufferers and reasonable accommodations to improve it. Quantitative and qualitative methods were applied; a survey-questionnaire, participatory-developed, was online-administered to a sample of self-reported FM sufferers (N = 1176). Then, two Focus Groups (FGs), involving 15 fibromyalgia-affected women, were held. Data were analyzed by a thematic analysis approach. Among survey-respondents, 20% were unemployed and only 14% went to work gladly. Variability of pain (84%) and fatigue (90%) were the most perceived reasons for difficulties at work. Negative relationships at work were reported by most participants. The FGs' discussions addressed different strategies for overcoming the main obstacle of "not being believed by colleagues and employers" and reasonable accommodations. However, a negative hopeless attitude towards the solution of problems at work was also apparent. Different critical issues in the workplace emerged from the survey and the FGs. Coordinated actions, according to a transdisciplinary approach, are needed to manage fibromyalgia-induced difficulties in the workplace.

Investigating Genetic and Environmental Substrates of the Relationship between Positive Mental Health and Biological Aging-A Study Protocol.

BACKGROUND: The Italian National Institute of Health (Istituto Superiore di Sanità) funded a 30-month project (July 2021-January 2024) to conduct a twin study of the relationships between Positive Mental Health (PMH) and cellular longevity. Only a few previous studies have focused on the biomarkers of aging in relation to psychological well-being, and none of them exploited the potential of the twin design. METHOD: In this project, following the standard procedures of the Italian Twin Registry (ITR), we aim to recruit 200 adult twin pairs enrolled in the ITR. They are requested to complete a self-report questionnaire battery on PMH and to undergo a blood withdrawal for the assessment of aging biomarkers, i.e., telomere length and mitochondrial DNA functionality. The association between psychological and aging biomarker measures will be assessed, controlling for genetic and familial confounding effects using the twin study design. RESULTS AND CONCLUSIONS: Biomarker assays are underway. Once data are available for the total study sample, statistical analyses will be performed. The project's results may shed light on new mechanisms underlying the mind-body connection and may prove helpful to promote psychological well-being in conjunction with biological functioning.

Environmental effects on brain functional networks in a juvenile twin population.

The brain's intrinsic organization into large-scale functional networks, the resting state networks (RSN), shows complex inter-individual variability, consolidated during development. Nevertheless, the role of gene and environment on developmental brain functional connectivity (FC) remains largely unknown. Twin design represents an optimal platform to shed light on these effects acting on RSN characteristics. In this study, we applied statistical twin methods to resting-state functional magnetic resonance imaging (rs-fMRI) scans from 50 young twin pairs (aged 10-30 years) to preliminarily explore developmental determinants of brain FC. Multi-scale FC features were extracted and tested for applicability of classical ACE and ADE twin designs. Epistatic genetic effects were also assessed. In our sample, genetic and environmental effects on the brain functional connections largely varied between brain regions and FC features, showing good consistency at multiple spatial scales. Although we found selective contributions of common environment on temporo-occipital connections and of genetics on frontotemporal connections, the unique environment showed a predominant effect on FC link- and node-level features. Despite the lack of accurate genetic modeling, our preliminary results showed complex relationships between genes, environment, and functional brain connections during development. A predominant role of the unique environment on multi-scale RSN characteristics was suggested, which needs replications on independent samples. Future investigations should especially focus on nonadditive genetic effects, which remain largely unexplored.

Stability and change in genetic and environmental influences on depressive symptoms in response to COVID-19 pandemic.

Background: The rapid spread of the new Coronavirus and the consequent restrictions to contain transmission generated an unprecedented psychological impact on the general population. The Italian Twin Registry performed a longitudinal study to investigate to what extent genetic and environmental influences contributed to changes in depressive symptoms. Methods: Data from adult twins were collected. All participants completed an online questionnaire including the 2-item Patient Health Questionnaire (PHQ-2) just before (February 2020) and immediately after the Italian lockdown (June 2020). Genetic modeling based on Cholesky decomposition was used to estimate the role of genetic (A) and both shared (C) and unshared (E) environmental factors in the observed longitudinal course of depressive symptoms. Results: Longitudinal genetic analysis was based on 348 twin pairs (215 monozygotic and 133 dizygotic pairs) with a mean age of 42.6 years (range 18-93 years). An AE Cholesky model provided heritability estimates for depressive symptoms of 0.24 and 0.35 before and after the lockdown period, respectively. Under the same model, the observed longitudinal trait correlation (0.44) was approximately equally contributed by genetic (46%) and unshared environmental (54%) influences, while longitudinal environmental correlation was lower than genetic correlation (0.34 and 0.71, respectively). Conclusions: Although the heritability of depressive symptoms was rather stable across the targeted time window, different environmental as well as genetic factors seemed to act before and after the lockdown, which suggests possible gene-environment interaction.

A Twin Study of the Relationships between Cognitive Disengagement Syndrome and Anxiety Phenotypes in Childhood and Adolescence.

Data on the etiological factors underlying the co-occurrence of Cognitive Disengagement Syndrome (CDS) with anxiety symptoms are very limited. The present study investigated the nature of latent shared etiological elements in 400 Italian twin pairs aged 8-18, explaining the covariation between CDS and anxiety symptoms. Preliminary analysis demonstrated significant correlations between Child Behaviour Checklist/6-18 Sluggish Cognitive Tempo Scale and two (Somatic Anxiety, Generalized Anxiety) out of five Screen for Child Anxiety Related Disorders anxiety subscales. Results from causal analysis seem to exclude the hypothesis that co-occurrence between CDS and Anxiety Symptoms could be due to a direct phenotypic effect of one trait upon the other. Model fitting-analysis indicated that the aforementioned associations were partially explained by shared genetic and environmental factors influencing a common liability factor. A latent variable capturing the covariation between CDS and anxiety problems can be considered as a unifying (patho)physiological mechanism/system common to these constructs. Our results support the adoption of a broader view of the relationships between CDS and anxiety phenotypes in childhood and adolescence for both clinicians and educators.

Age-Related Variations of Genetic and Environmental Contributions to the Covariation of Fear, Distress and Externalizing Symptoms: A Twin Study in Childhood and Adolescence.

The frequency with which Internalizing and Externalizing symptoms co-occur suggests that, behind both domains, there may be a common susceptibility represented by a general psychopathology factor. However, it's still unclear whether this common susceptibility is affected by age-related variations. Internalizing (i.e., Fear and Distress) and Externalizing symptoms were evaluated in 803 twin pairs from the population-based Italian Twin Registry. Model-fitting analysis was performed separately in the 6-14 and 15-18 age groups to estimate genetic and environmental contributions to the covariance among symptoms. For the 6-14 group, a multivariate Cholesky model best fitted the data, while, for the 15-18 group, the best fit was provided by a Common Pathway model in which nearly 50% of total variance of each trait was mediated by common genetic factors. Our findings support a common susceptibility behind Internalizing and Externalizing symptoms, mainly genetic in origin, that becomes more evident at the beginning of puberty.

A multi-marker integrative analysis reveals benefits and risks of bariatric surgery.

Bariatric surgery (BS) is an effective intervention for severe obesity and associated comorbidities. Although several studies have addressed the clinical and metabolic effects of BS, an integrative analysis of the complex body response to surgery is still lacking. We conducted a longitudinal data study with 36 patients with severe obesity who were tested before, 6 and 12 months after restrictive BS for more than one hundred blood biomarkers, including clinical, oxidative stress and metabolic markers, peptide mediators and red blood cell membrane lipids. By using a synthetic data-driven modeling based on principal component and correlation analyses, we provided evidence that, besides the early, well-known glucose metabolism- and weight loss-associated beneficial effects of BS, a tardive, weight-independent increase of the hepatic cholesterol metabolism occurs that is associated with potentially detrimental inflammatory and metabolic effects. Canonical correlation analysis indicated that oxidative stress is the most predictive feature of the BS-induced changes of both glucose and lipids metabolism. Our results show the power of multi-level correlation analysis to uncover the network of biological pathways affected by BS. This approach highlighted potential health risks of restrictive BS that are disregarded with the current practice to use weight loss as surrogate of BS success.

An Italian Twin Study of Non-Cancer Chronic Pain as a Wide Phenotype and Its Intensity.

Background and Objectives: Non-cancer chronic pain (CP) results from the interaction between genetic and environmental factors. Twin studies help to estimate genetic and environmental contributions to complex traits such as CP. To date, twin studies on the heritability of pain phenotypes have relied almost exclusively on specific diagnoses, neglecting pain intensity. This study aims to estimate the genetic and environmental contributions to CP occurrence as a wide phenotype and its intensity among a non-clinical population. Materials and Methods: A nationwide online survey was conducted in February 2020 on 6000 adult twins enrolled in the Italian Twin Registry. A five-item questionnaire, designed and validated by our study group, was administered to detect the CP condition along with its intensity, underlying causes or triggers, treatments, and self-perceived efficacy. The twin study design was used to infer the relative weight of genes and environment on CP occurrence and intensity, and biometrical modelling was applied to these phenotypes. Results: A total of 3258 twins, aged ≥18, replied to the online survey (response rate 54%). These included 762 intact pairs (mean age: 39 years; age range: 18-82 years; 34% male; CP prevalence: 24%), of whom 750 pairs were subjected to biometrical modelling after the exclusion of pairs with either unknown zygosity or cancer-associated CP. Broad-sense heritability estimates were driven by non-additive genetic effects and were 0.36 (0.19-0.51) for CP occurrence and 0.31 (0.16-0.44) for CP intensity. No evidence emerged for either sex differences in genetic and environmental variance components or interactions of these components with age. Conclusions: Moderate non-additive genetic components were suggested for non-cancer CP occurrence and its intensity. These results encourage further research on the gene-gene interactions underlying CP liability and associated phenotypes, and also strengthen the need for prevention strategies to avoid CP occurrence or to decrease pain intensity.

Development and Validation of the Italian "Brief Five-Item Chronic Pain Questionnaire" for Epidemiological Studies.

Background: Chronic pain (CP) prevalence estimates addressing a wide phenotype are still quite fragmented and may vary widely due to the lack of standardized tools of investigation. There is an urgent need to update general population CP estimates. Methods: For this purpose, the Brief Five-item Chronic Pain Questionnaire was developed through experts' consultations for design and content validity assessment; literature analysis of measures used to investigate CP for general population surveys; understandability evaluation through a survey on a convenience sample of affected and non-affected individuals; reliability assessment by means of two double-wave online surveys carried out by the Italian Twin Registry; criterion and construct validity assessment through the third wave of the 2019 European Health Interview Survey (Ehis). Results: Key dimensions were defined to describe CP main aspects from a public health perspective. Literature analysis showed that validated questionnaires were rarely used to address important public health CP aspects. Understandability of the measure was good. Test-retest analyses showed adequate reliability of the measure: k values were at least "moderate" with highest values regarding CP "occurrence" and "intensity". Correlations of CP with well-known comorbidities (cancer, depression), and specific traits (age, education) as well as of CP and its intensity with "physical pain occurrence and intensity" detected in the Ehis 2019, confirmed, respectively, a good construct and criterion validity. Construct validity was also evaluated through the correlation between "perceived treatment effectiveness" and "interference of pain in daily life activities" as recorded in the Ehis 2019. Conclusion: The designed questionnaire is a brief self-administered measure, particularly suitable to detect persistent states of pain and related intensity in large-scale general population surveys by means of a first filtering item followed by four further items. It is, in fact, designed to detect CP possible underlying causes/triggers, drugs/treatments taking and frequency, and self-perceived effectiveness among CP sufferers. Further validation of the measure in different social and cultural contexts is desirable.

Genetic and environmental contributions to psychopathological symptoms stability and change across the COVID-19 pandemic.

Several longitudinal studies investigated changes in mental health related to the pandemic event. However, little research has focused on the mediating role of environmental and genetic factors. The current prospective study aimed to evaluate the genetic and environmental contributions to the stability of symptoms of depression, anxiety and stress during the COVID-19 crisis. A total of 798 adult twins, previously enrolled in the Italian Twin Register, participated in the study and completed on-line questionnaires sent out on June 2020 and December 2020. The nine-item Patient Health Questionnaire (PHQ-9), the six-item State-Trait Anxiety Inventory (STAI-6), and the Impact of Event Scale - Revised (IES-R) were administered to assess depressive and anxiety symptoms, and pandemic-related subjective distress, respectively. A considerable longitudinal stability was observed for each trait (range: 0.57, STAI-6 - 0.67, PHQ-9). Bivariate Cholesky decomposition indicated that genetic factors explained from 53% (IES-R) to 61% (STAI-6) of between-wave covariance and that genetic overlap between the two waves was almost complete (range: 0.91, STAI-6 - 0.99, PHQ-9). Our findings support the hypothesis, at least over the 6-month period examined, of a genetic stability between waves and of an environmental discontinuity due to changes in life conditions during the pandemic.

The COVID-19 pandemic in Italy: Depressive symptoms immediately before and after the first lockdown.

BACKGROUND: Italy was one of the first countries to be heavily hit by the spread of the new Coronavirus. Longitudinal studies are needed to investigate the real effect of COVID-19 on adult mental health. The Italian Twin Registry carried out a study to investigate, over time, the course of depressive symptoms in the general population. METHODS: The study relies on data collected just before the beginning (February 2020) and the end (June 2020) of the first lockdown. Symptoms of depression were assessed using the Patient Health Questionnaire, and total scores or categorized depression scores were considered in the analyzes. RESULTS: A total of 1690 adult twins were recruited. The study showed a mean depression score of 1.11 immediately before lockdown and 1.20 immediately after, with an overall prevalence of depressive symptoms increasing from 33.6 to 38.9%. Depressive symptoms immediately after the restriction period were associated with Covid-19 symptoms affecting households, financial problems due to the pandemic and poor social support. Independently of the baseline risk of depressive symptoms, we observed an increased risk among younger and less educated people. Compared to the pre-lockdown period, women and middle-aged people also were found to be at greater risk of developing depressive symptoms. LIMITATIONS: Possible participation bias and residual selection bias. CONCLUSIONS: The study shows that the COVID-19 pandemic was associated with an increased depressive symptomatology and that, in such health emergency times, the most vulnerable persons are young adults, women, and those living in a socially, culturally, or economically disadvantaged environment.

Adolescent pain, anxiety, and depressive problems: a twin study of their co-occurrence and the relationship to substance use.

ABSTRACT: Data on the etiological factors underlying the co-occurrence of common adolescent pain with anxiety and depression symptoms are very limited. Opioid prescriptions for adolescent pain problems are on the rise in North America and constitute a risk factor for diversion, misuse, and substance use. In this study, we aimed to investigate the phenotypic and etiological association among pain, depression, and anxiety and to test their link to substance use in adolescents. By taking advantage of the Italian National Twin Registry and of the relatively low incidence of opioid prescriptions in Italy, we applied multivariate modelling analyses to 748 Italian adolescent twins (374 pairs, mean age 16 ± 1.24 years). Twins' responses to the Achenbach Youth Self-Report questionnaire were used to build a composite adolescent pain index and to measure anxiety, depression, and substance use. All monozygotic within-pair correlations were higher than the dizygotic correlations, indicating genetic influences for adolescent pain, anxiety, and depressive problems. A common latent liability factor influenced by genetic and environmental elements shared among pain, depression, and anxiety provided the best fit to explain the co-occurrence of adolescent pain, anxiety, and depression problems. A common phenotypic factor capturing all 3 phenotypes was positively associated (ß = 0.19, P < 0.001, confidence interval: 0.10-0.27) with substance use. These findings indicate that several intertwined mechanisms, including genetic factors, can explain a shared liability to common adolescent pain, anxiety, and depression problems. Their association with substance use remains traceable even in societies with relatively low prevalence of opioid prescriptions.

Genetic and Environmental Architecture of Five Factor Model and Super-Factors: An Italian Twin Study.

No previous research explored the genetic and environmental structure of Big Five dimensions of personality and higher-order factors in a single twin study, except, in part, for just one study. We used the twin design to estimate the effects of genes and environment on both Five Factor model and related second- and third-order factors (i.e., Alpha [stability], Beta [plasticity], and GFP [general factor of personality]). We analyzed data from 314 adult twins (157 pairs: 83 monozygotic, 74 dizygotic; mean age: 52 years) enrolled in the Italian Twin Register. Participants underwent clinical and instrumental evaluations, and completed a 25-adjective list drawn from the Short Adjectives Checklist to Measure Big Five (SACBIF). We applied quantitative genetic models to unravel the sources of variation and covariation for the Big Five and higher-order factors. We found a similar etiological architecture across the different levels of analysis, with moderate to substantial non-additive genetic and unique environmental influences on all the personality traits, and no shared environmental contribution for any of them. We also detected significant genetic correlations for the Big Five dimensions and the Alpha and Beta super-factors. With some limitations, our results suggest that the etiological architecture of personality may be invariant to the factor level of analysis.

Intestinal Permeability and Circulating CD161+CCR6+CD8+T Cells in Patients With Relapsing-Remitting Multiple Sclerosis Treated With Dimethylfumarate.

Background: The changes of the gut-brain axis have been recently recognized as important components in multiple sclerosis (MS) pathogenesis. Objectives: To evaluate the effects of DMF on intestinal barrier permeability and mucosal immune responses. Methods: We investigated intestinal permeability (IP) and circulating CD161+CCR6+CD8+T cells in 25 patients with MS, who met eligibility criteria for dimethyl-fumarate (DMF) treatment. These data, together with clinical/MRI parameters, were studied at three time-points: baseline (before therapy), after one (T1) and 9 months (T2) of treatment. Results: At baseline 16 patients (64%) showed altered IP, while 14 cases (56%) showed active MRI. During DMF therapy we found the expected decrease of disease activity at MRI compared to T0 (6/25 at T1, p = 0.035 and 3/25 at T2, p < 0.00), and a reduction in the percentage of CD161+CCR6+CD8+ T cells (16/23 at T2; p < 0.001). The effects of DMF on gut barrier alterations was variable, without a clear longitudinal pattern, while we found significant relationships between IP changes and drop of MRI activity (p = 0.04) and circulating CD161+CCr6+CD8+ T cells (p = 0.023). Conclusions: The gut barrier is frequently altered in MS, and the CD161+ CCR6+CD8+ T cell-subset shows dynamics which correlate with disease course and therapy.

Attitude of potential biobank donors screened for depression towards disclosure of individual health results.

BACKGROUND: Research based on biological material with linked health and clinical data may produce new strategies for disease prevention, diagnosis and treatment. A survey was conducted among individuals previously screened for major depressive disorder (MDD) to explore participants' attitude towards research biobanking. METHODS: The survey used self-report questionnaires about donation for research biobanks, self-perceived health and life satisfaction. Means and percentages were compared across groups by using t test, ANOVA and chi-square test. RESULTS: Of 416 subjects who underwent the MDD screening, 51 (12.2%) responded to the survey, with the majority of them (42) agreeing to the use of their biological samples only in absence of feedbacks about health or diseases. Agreement towards biobanking was not affected by life satisfaction or self-perceived health. CONCLUSIONS: Our findings show a prevailing preference against health results disclosure among MDD-screened subjects, suggesting a role of personal - particularly psychosocial - factors in research biobanking individuals' contribution.

Genetic and environmental factors on heart rate, mean arterial pressure and carotid intima-media thickness: A longitudinal twin study.

BACKGROUND: Heart rate (HR), mean arterial pressure (MAP) and carotid intima-media thickness (cIMT) are moderately heritable cardiovascular traits, but the environmental effects on the longitudinal change of their heritability have never been investigated. METHODS: 368 Italian and Hungarian twins (107 monozygotic, 77 dizygotic) underwent oscillometric measurement and B-mode sonography of bilateral carotid arteries in 2009/2010 and 2014. Within- -individual/cross-study wave, cross-twin/within-study wave and cross-twin/cross-study wave correlations were estimated, and bivariate Cholesky models were fitted to decompose the total variance at each wave and covariance between study waves into additive genetic, shared and unique environmental components. RESULTS: For each trait, a moderate longitudinal stability was observed, with within-individual/crosswave correlations of 0.42 (95% CI: 0.33-0.51) for HR, 0.34 (95% CI: 0.24-0.43) for MAP, and 0.23 (95% CI: 0.12-0.33) for cIMT. Cross-twin/cross-wave correlations in monozygotic pairs were all significant and substantially higher than the corresponding dizygotic correlations. Genetic continuity was the main source of longitudinal stability, with across-time genetic correlations of 0.52 (95% CI: 0.29-0.71) for HR, 0.56 (95% CI: 0.31-0.81) for MAP, and 0.36 (95% CI: 0.07-0.64) for cIMT. Overlapping genetic factors explained respectively 57%, 77%, and 68% of the longitudinal covariance of the HR, MAP and cIMT traits. CONCLUSIONS: Genetic factors have a substantial role in the longitudinal change of HR, MAP and cIMT; however, the influence of unique environmental factors remains relevant. Further studies should better elucidate whether epigenetic mechanisms have a role in influencing the stability of the investigated traits over time.