Australian Twin Research Articles

Anorexia nervosa polygenic risk, beyond diagnoses: relationship with adolescent disordered eating and behaviors in an Australian female twin population.

It is well established that there is a substantial genetic component to eating disorders (EDs). Polygenic risk scores (PRSs) can be used to quantify cumulative genetic risk for a trait at an individual level. Recent studies suggest PRSs for anorexia nervosa (AN) may also predict risk for other disordered eating behaviors, but no study has examined if PRS for AN can predict disordered eating as a global continuous measure. This study aimed to investigate whether PRS for AN predicted overall levels of disordered eating, or specific lifetime disordered eating behaviors, in an Australian adolescent female population. PRSs were calculated based on summary statistics from the largest Psychiatric Genomics Consortium AN genome-wide association study to date. Analyses were performed using genome-wide complex trait analysis to test the associations between AN PRS and disordered eating global scores, avoidance of eating, objective bulimic episodes, self-induced vomiting, and driven exercise in a sample of Australian adolescent female twins recruited from the Australian Twin Registry (N = 383). After applying the false-discovery rate correction, the AN PRS was significantly associated with all disordered eating outcomes. Findings suggest shared genetic etiology across disordered eating presentations and provide insight into the utility of AN PRS for predicting disordered eating behaviors in the general population. In the future, PRSs for EDs may have clinical utility in early disordered eating risk identification, prevention, and intervention.

Twin Data Support a Sensitive Period for Singing Ability.

As with many other musical traits, the social environment is a key influence on the development of singing ability. While the familial singing environment is likely to be formative, its role relative to other environmental influences such as training is unclear. We used structural equation modeling to test relationships among demographic characteristics, familial environmental variables (early and current singing with family), vocal training, and singing ability in a large, previously documented sample of Australian twins (N = 1163). Notably, early singing with family, and to a lesser extent vocal training, predicted singing ability, whereas current singing with family did not. Early familial singing also mediated the relationship between sex and singing ability, with men who sang less with family during childhood showing poorer ability. Bivariate twin models between early familial singing and singing ability showed the phenotypic correlation was largely explained by shared environmental influences. This raises the possibility of a sensitive period for singing ability, with sociocultural expectations around singing potentially differentiating the developmental trajectories of this skill for men and women.

Identifying a Birth Cohort of Twins from Linked Data – Challenges and Opportunities

ObjectiveIn the absence of accurate perinatal records, identifying and differentiating twins in administrative records is difficult because of their similarity; they share surnames, dates of birth, and residences. In administrative databases, events within twin pairs are often incorrectly identified as being from one individual, representing a threat to data accuracy. An inability to identify twins in administrative data precludes applying powerful twin-based causal inference methods to understand health and social well-being. ApproachWe developed an algorithm using linked administrative birth, perinatal, emergency department, and hospital records in Victoria, Australia from 1 January 1993 to 31 December 2023. We probabilistically linked a sample of 1,434 ‘known’ twin pairs from the Australian Twin Registry to validate the sensitivity of our algorithm. We calculated specificity using a sample of non-twins derived from linked data. ResultsOur algorithm identified 37,900 twin pairs, 75,800 twin individuals, in the Victorian linked dataset. The accuracy of our ascertainment of twins by key characteristics will be presented and discussed. ConclusionsThe birth cohort we have generated is one of the largest twin cohorts in the world with unprecedented granularity in longitudinal health and social data. ImplicationsOur algorithm improves the accuracy of administrative data repositories and linkage, providing novel information on where errors in previous linkages have occurred due to limited familial or intergenerational information. Our large population-based birth cohort of twins can be used to investigate the familial and non-familial determinants of health using advanced causal inference which leverages the natural similarity between twins.

Differential etiologic associations of heroin use and prescription opioid misuse with psychopathology.

Patterns of association with externalizing and internalizing features differ across heroin use and prescription opioid misuse (POM). The present study examined whether heroin use and POM display differential etiologic overlap with symptoms of conduct disorder (CD), adult antisocial behavior (AAB), and major depressive episodes (MDEs), how aggregating heroin use and POM into a single phenotype may bias results, and explored potential sex differences. Seven thousand one hundred and sixty-four individual twins from the Australian Twin Registry (ATR; 59.81% female; Mage = 30.58 years) reported lifetime heroin use, POM, CD symptoms, AABs, and MDE symptoms within a semi-structured interview. Biometric models decomposed phenotypic variance and covariance into additive genetic, common environmental, and unique environmental effects. The proportion of variance in heroin use attributable to factors shared with CD, AAB, and MDE, respectively, was 41%, 41%, and 0% for men and 26%, 19%, and 42% for women; for POM, the proportions were 33%, 35%, and 20% for men and 15%, 9%, and 13% for women. CD and AAB were more strongly genetically correlated with heroin use among women and with POM among men. MDE was more strongly genetically correlated with POM than with heroin use among men, but more strongly genetically correlated with heroin use than with POM among women. Analyses using an aggregate opioid (mis)use variable were biased toward POM, which was the more prevalent phenotype. Magnitude and source of etiologic influence may differ across forms of opioid (mis)use and sex. Disaggregating heroin use and POM in future opioid research may be warranted. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Abstract PO4-08-06: Causal Relationships and Familial Aggregation of Mammogram Risk Scores: Insights from Breast Cancer in Twins and Families

Abstract Background: Mammogram risk scores based on texture and density, determined by brightness thresholds, are associated with breast cancer risk differently and could reveal distinct information about breast cancer risk. This study aimed to investigate the causal relationships between these intercorrelated risk scores and the familial aggregation of a texture-based mammogram measure, shedding light on the relevance to breast cancer aetiology. Methods: We analysed data from the Australian Mammographic Density Twins and Sisters Study, including 3195 breast-cancer-free women from 1519 families. The dataset comprised 527 pairs of monozygotic (MZ) twins, 271 pairs of dizygotic (DZ) twins, and 1599 sisters. The average age at mammography for sister pairs ranged from 40 to 70 years. Mammogram risk scores based on texture (named Cirrus) and three density-defined areas (light, bright, and brightest) that were spatially independent were generated. The Inference about Causation from Examination of Familial Confounding (ICE FALCON) method was employed for causal inference. Familial aggregation and the variance of Cirrus were assessed as a function of age using a multivariate normal model for pedigree analysis. The classic twin model was employed but allowing for varying shared environmental effects among different sister pairs. The single-nucleotide polymorphism (SNP)-based heritability was estimated using genetic variants from both closely and distantly related individuals. Model fits were compared using likelihood ratio tests and the Akaike Information Criterion. Results: Causal analysis using ICE FALCON revealed significant positive causal effects, with Cirrus, light areas, and bright areas influencing the brightest areas (accounting for 34%, 55%, and 85% of the associations, respectively). Similarly, light areas and bright areas demonstrated causal effects on Cirrus (accounting for 37% and 28% of the associations, respectively). No age-related differences in familial correlations or Cirrus variance were found for women aged 40 to 70 years. Familial correlations were estimated at 0.51 (0.03) for MZ pairs and 0.16 (0.03) for combined DZ and non-twin sister pairs, with no significant difference between DZ and non-twin sister pairs (P=0.3). Additive genetic effects accounted for up to 32% (5%) of the variance, consistent with SNP-based heritability estimates of 36% (12%). MZ-specific environmental effects contributed to at least 20% (3%), while shared environmental effects for DZ and non-twin sibling pairs accounted for less than 40% of that for MZ pairs. Conclusion: In a mammogram, the lighter (less dense) areas causally influence the brightest (highly dense) areas, including through textural features. These causal relationships provide insights into the relative importance of different mammogram features in breast cancer aetiology. For example, the brightest areas are more aetiologically important for screen-detected breast cancer, while the light areas are more aetiologically important for interval breast cancer. Additionally, specific textural features capture aetiologically independent breast cancer risk information from dense areas. We also confirm the partial heritability of Cirrus, the texture-based mammogram measure, substantially influenced by environmental factors (familial and non-familial). As well as genetic factors, Cirrus could be determined by factors operating at times of life when MZ pairs share their environments to a greater extent than do DZ and non-twin sisters, starting in utero and prior to adulthood, and remaining constant thereafter. These insights from twin and family data enhance our understanding of mammogram risk scores and their implications for breast cancer risk assessment. Citation Format: Zhoufeng Ye, Shuai Li, Gill Dite, Tuong Nguyen, Robert MacInnis, John Hopper. Causal Relationships and Familial Aggregation of Mammogram Risk Scores: Insights from Breast Cancer in Twins and Families [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-08-06.

Genetic and shared environmental factors explain the association between adolescent polysubstance use and high school noncompletion.

Examine the nature of the relationship between adolescent polysubstance use and high school noncompletion. Among a sample of 9,579 adult Australian twins (58.63% female, Mage = 30.59), we examined the association between the number of substances used in adolescence and high school noncompletion within a discordant twin design and bivariate twin analysis. In individual-level models controlling for parental education, conduct disorder symptoms, childhood major depression, sex, zygosity, and cohort, each additional substance used in adolescence was associated with a 30% increase in the odds of high school noncompletion (OR = 1.30 [1.18, 1.42]). Discordant twin models found that the potentially causal effect of adolescent use on high school noncompletion was nonsignificant (OR = 1.19 [0.96, 1.47]). Follow-up bivariate twin models suggested genetic (35.4%, 95% CI [24.5%, 48.7%]) and shared environmental influences (27.8%, 95% CI [12.7%, 35.1%]) each contributed to the covariation in adolescent polysubstance use and early school dropout. The association between polysubstance use and early school dropout was largely accounted for by genetic and shared environmental factors, with nonsignificant evidence for a potentially causal association. Future research should examine whether underlying shared risk factors reflect a general propensity for addiction, a broader externalizing liability, or a combination of the two. More evidence using finer measurement of substance use is needed to rule out a causal association between adolescent polysubstance use and high school noncompletion. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Genetic effects on variability in visual aesthetic evaluations are partially shared across visual domains

The aesthetic values that individuals place on visual images are formed and shaped over a lifetime. However, whether the formation of visual aesthetic value is solely influenced by environmental exposure is still a matter of debate. Here, we considered differences in aesthetic value emerging across three visual domains: abstract images, scenes, and faces. We examined variability in two major dimensions of ordinary aesthetic experiences: taste-typicality and evaluation-bias. We build on two samples from the Australian Twin Registry where 1547 and 1231 monozygotic and dizygotic twins originally rated visual images belonging to the three domains. Genetic influences explained 26% to 41% of the variance in taste-typicality and evaluation-bias. Multivariate analyses showed that genetic effects were partially shared across visual domains. Results indicate that the heritability of major dimensions of aesthetic evaluations is comparable to that of other complex social traits, albeit lower than for other complex cognitive traits. The exception was taste-typicality for abstract images, for which we found only shared and unique environmental influences. Our study reveals that diverse sources of genetic and environmental variation influence the formation of aesthetic value across distinct visual domains and provides improved metrics to assess inter-individual differences in aesthetic value.

The heritability of subjective cognitive complaints in older Australian twins

AbstractBackgroundSubjective cognitive complaints (SCCs) may be a precursor to mild cognitive impairment (MCI) and dementia. This study aimed to examine the heritability of SCCs, and the influence of personality and mood on the relationship between SCCs and memory performance.MethodThe heritability of SCCs were examined in 306 twin pairs using structural equation modelling. Genetic, environmental, and phenotypic correlations between SCCs and memory performance, personality, and mood scores were determined.ResultSCCs were low to moderately heritable. Mood appeared to be related to SCCs by an environmental correlation, whereas memory performance was related to SCCs by a genetic correlation. SCCs had a significant amount of both genetic and environmental variances not explained by memory performance, personality, or mood.ConclusionOur results suggest that SCCs are influenced both by a person’s mood and their memory performance, and that these determinants are not mutually exclusive. Much of the genetic and environmental components to SCCs were specific to SCCs, with the specific factors yet to be determined.

How accurate are self-evaluations of singing ability?

Research has shown that people inaccurately assess their own abilities on self-report measures, including academic, athletic, and music ability. Evidence suggests this is also true for singing, with individuals either overestimating or underestimating their level of singing competency. In this paper, we present the Melbourne Singing Tool Questionnaire (MST-Q), a brief 16-item measure exploring people's self-perceptions of singing ability and engagement with singing. Using a large sample of Australian twins (n = 996), we identified three latent factors underlying MST-Q items and examined whether these factors were related to an objective phenotypic measure of singing ability. The three factors were identified as Personal Engagement, Social Engagement, and Self-Evaluation. All factors were positively associated with objective singing performance, with the Self-Evaluation factor yielding the strongest correlation (r = 0.66). Both the Self-Evaluation factor and a single self-report item of singing ability shared the same predictive strength. Contrary to expectations, our findings suggest that self-evaluation strongly predicts singing ability, and this self-evaluation is of higher predictive value than self-reported engagement with music and singing.

Causal relationships between breast cancer risk factors based on mammographic features

BackgroundMammogram risk scores based on texture and density defined by different brightness thresholds are associated with breast cancer risk differently and could reveal distinct information about breast cancer risk. We aimed to investigate causal relationships between these intercorrelated mammogram risk scores to determine their relevance to breast cancer aetiology.MethodsWe used digitised mammograms for 371 monozygotic twin pairs, aged 40–70 years without a prior diagnosis of breast cancer at the time of mammography, from the Australian Mammographic Density Twins and Sisters Study. We generated normalised, age-adjusted, and standardised risk scores based on textures using the Cirrus algorithm and on three spatially independent dense areas defined by increasing brightness threshold: light areas, bright areas, and brightest areas. Causal inference was made using the Inference about Causation from Examination of FAmilial CONfounding (ICE FALCON) method.ResultsThe mammogram risk scores were correlated within twin pairs and with each other (r = 0.22–0.81; all P < 0.005). We estimated that 28–92% of the associations between the risk scores could be attributed to causal relationships between the scores, with the rest attributed to familial confounders shared by the scores. There was consistent evidence for positive causal effects: of Cirrus, light areas, and bright areas on the brightest areas (accounting for 34%, 55%, and 85% of the associations, respectively); and of light areas and bright areas on Cirrus (accounting for 37% and 28%, respectively).ConclusionsIn a mammogram, the lighter (less dense) areas have a causal effect on the brightest (highly dense) areas, including through a causal pathway via textural features. These causal relationships help us gain insight into the relative aetiological importance of different mammographic features in breast cancer. For example our findings are consistent with the brightest areas being more aetiologically important than lighter areas for screen-detected breast cancer; conversely, light areas being more aetiologically important for interval breast cancer. Additionally, specific textural features capture aetiologically independent breast cancer risk information from dense areas. These findings highlight the utility of ICE FALCON and family data in decomposing the associations between intercorrelated disease biomarkers into distinct biological pathways.

Beneficial and harmful effects of physical activity on care-seeking for low back pain: the AUTBACK study

PurposePeople who seek more care for low back pain (LBP) tend to experience poorer recovery (e.g. higher pain and disability levels). Understanding the factors associated with care-seeking for LBP might improve patient outcomes and potentially alleviate the burden of LBP on global health systems. This study aimed to investigate the relationship between different intensities, volumes, and domains of physical activity and care-seeking behaviours, in people with a history of LBP.MethodsLongitudinal data from adult twins were drawn from the AUstralian Twin BACK study. The primary outcome was the total self-reported frequency (counts) of overall utilisation of care for LBP, over 1 year. Secondary outcomes were the utilisation of health services, and the utilisation of self-management strategies, for LBP (assessed as total frequency over 1 year). Explanatory variables were device-based measures of sedentary behaviour and moderate-to-vigorous intensity physical activity, and self-reported physical workload, and work, transport, household, and leisure domain physical activity, at baseline.ResultsData from 340 individuals were included. Median age was 56.4 years (IQR 44.9–62.3 years) and 73% of participants were female. Medium-to-high baseline volumes of sedentary behaviour were significantly associated with greater counts of overall care utilisation (IRR 1.60, 95%CI 1.04–2.44) and utilisation of self-management strategies (IRR 1.60, 95%CI 1.02–2.50) for LBP, over 1 year. Medium-to-high baseline volumes of household domain physical activity were significantly associated with greater counts of utilising self-management strategies for LBP over 1 year (IRR 1.62, 95%CI 1.04–2.53). No explanatory variables were associated with the utilisation of health services for LBP.ConclusionPeople who engage in higher baseline volumes of sedentary behaviour or physical activity in the household setting (e.g. housework, gardening, yard work, general household maintenance) utilise 1.6 times more care for LBP over 1 year. Findings suggest that higher volumes of these behaviours may be harmful for LBP. No intensities, volumes, or domains of physical activity demonstrated clear benefits for LBP. Where feasible, patients and clinicians should collaborate to screen and develop strategies to reduce engagement in sedentary behaviour or physical activity in the household setting. Contextual factors (e.g. patient symptom severity, sociocultural roles, occupational demands) should be considered when devising appropriate behaviour change strategies.

The impact of aggregate positive lifestyle behaviors on low back pain resilience and care seeking

BACKGROUND CONTEXTLow back pain (LBP) is a global issue, and the high associated costs are mainly attributed to a small proportion of people with LBP who seek care. Importantly, the impact of aggregate positive lifestyle behaviors on LBP resilience and care seeking is not known. PURPOSEThis study aimed to evaluate the relationship between positive lifestyle behaviors and LBP resilience. STUDY DESIGNThis study was a prospective longitudinal cohort study. PATIENT SAMPLEData was collected as part of the AUstralian Twin BACK Study (AUTBACK). Participants who reported a lifetime previous history of LBP at baseline were included in this analysis (n = 340). OUTCOME MEASURESThe outcomes of interest were the number of weeks without activity limiting LBP and total number of days of healthcare usage, health practitioner care, self-management care, and medication intake. METHODSA lifestyle behavior score was built using variables of body mass index (BMI), physical activity, smoking status, and sleep quality. Negative binomial regression analyses were used to assess the relationship between the positive lifestyle behavior score and the count outcomes of number of weeks without activity limiting LBP and number of days participants used care. RESULTSAfter adjusting for covariates, no association was found between participants’ positive lifestyle behavior score and their number of weeks without activity limiting LBP (IRR: 1.02, 95% CI 1.00–1.05). There was a statistically significant relationship between higher positive lifestyle behavior scores and fewer number of days of participants’ total healthcare usage (IRR:0.69, 95% CI 0.56–0.84), healthcare practitioner visits (IRR:0.62, 95% CI 0.45–0.84), use of self-management strategies (IRR:0.74, 95% CI 0.60–0.91), and use of pain medication (IRR:0.55, 95% CI 0.44–0.68). CONCLUSIONPeople who adopt optimal lifestyle behaviors, such as engaging in adequate physical activity, achieving optimal quality sleep, maintaining an ideal BMI, and not smoking, may not experience less time suffering from activity limiting LBP, but are less likely to use healthcare and pain medication for their LBP.

Correlated compound geometric frailty models based on reversed hazard rate

Frailty models are used in the survival analysis to account for the unobserved heterogeneity in individual risks to disease and death. To analyze the bivariate data on related survival times (e.g. matched pairs experiments, twin or family data), the shared frailty models were suggested. Shared frailty models are used despite their limitations. To overcome their disadvantages correlated frailty models may be used. In this paper, we introduce the correlated compound geometric frailty models based on reversed hazard rate with three different baseline distributions namely, the generalized log-logistic type I, the generalized log-logistic type II and the modified inverse Weibull. We introduce the Bayesian estimation procedure using Markov Chain Monte Carlo (MCMC) technique to estimate the parameters involved in these models. We present a simulation study to compare the true values of the parameters with the estimated values. We also apply the proposed models to the Australian twin data set and a better model is suggested.

On Modeling Bivariate Left Censored Data Using Reversed Hazard Rates

In this paper, we propose a model for analysing the bivariate left-censored data incorporating the dependence enjoyed between the components. This is achieved through the dynamic bivariate vector reversed hazard rate by Gürler (J Am Stat Assoc 91:1152–1165, 1996). The properties of the proposed model is studied. The maximum likelihood method of estimation and the Bayesian method of estimation of parameters is presented. The complexity of the likelihood function is handled through the Metropolis - Hastings algorithm. Interval estimation techniques of the parameters are also considered. Applications of this model is demonstrated by illustrating the usefulness of the model in analysing Australian twin dataset (Duffy in Am J Human Genet 47:530, 1990).

The Heritability of Subjective Cognitive Complaints in Older Australian Twins.

Subjective cognitive complaints (SCCs) may be a precursor to mild cognitive impairment (MCI) and dementia. This study aimed to examine the heritability of SCCs, correlations between SCCs and memory ability, and the influence of personality and mood on these relationships. Participants were 306 twin pairs. The heritability of SCCs and the genetic correlations between SCCs and memory performance, personality, and mood scores were determined using structural equation modelling. SCCs were low to moderately heritable. Memory performance, personality and mood were genetically, environmentally, and phenotypically correlated with SCCs in bivariate analysis. However, in multivariate analysis, only mood and memory performance had significant correlations with SCCs. Mood appeared to be related to SCCs by an environmental correlation, whereas memory performance was related to SCCs by a genetic correlation. The link between personality and SCCs was mediated by mood. SCCs had a significant amount of both genetic and environmental variances not explained by memory performance, personality, or mood. Our results suggest that SCCs are influenced both by a person's mood and their memory performance, and that these determinants are not mutually exclusive. While SCCs had genetic overlap with memory performance and environmental association with mood, much of the genetic and environmental components that comprised SCCs were specific to SCCs, though these specific factors are yet to be determined.

Specificity in genetic and environmental risk for prescription opioid misuse and heroin use.

Many studies aggregate prescription opioid misuse (POM) and heroin use into a single phenotype, but emerging evidence suggests that their genetic and environmental influences may be partially distinct. In total, 7164 individual twins (84.12% complete pairs; 59.81% female; mean age = 30.58 years) from the Australian Twin Registry reported their lifetime misuse of prescription opioids, stimulants, and sedatives, and lifetime use of heroin, cannabis, cocaine/crack, illicit stimulants, hallucinogens, inhalants, solvents, and dissociatives via telephone interview. Independent pathway models (IPMs) and common pathway models (CPMs) partitioned the variance of drug use phenotypes into general and drug-specific genetic (a), common environmental (c), and unique environmental factors (e). An IPM with one general a and one general e factor and a one-factor CPM provided comparable fit to the data. General factors accounted for 55% (a = 14%, e = 41%) and 79% (a = 64%, e = 15%) of the respective variation in POM and heroin use in the IPM, and 25% (a = 12%, c = 8%, e = 5%) and 80% (a = 38%, c = 27%, e = 15%) of the respective variation in POM and heroin use in the CPM. Across both models, POM emerged with substantial drug-specific genetic influence (26-39% of total phenotypic variance; 69-74% of genetic variance); heroin use did not (0% of total phenotypic variance; 0% of genetic variance in both models). Prescription sedative misuse also demonstrated significant drug-specific genetic variance. Genetic variation in POM, but not heroin use, is predominantly drug-specific. Misuse of prescription medications that reduce experiences of subjective distress may be partially influenced by sources of genetic variation separate from illicit drug use.

Association between physical activity, sedentary behaviour and the trajectory of low back pain

BACKGROUNDLow back pain (LBP) is one of the world's most prevalent health issues. Patients with LBP experience various intensities and durations of symptoms, which can lead to distinctive course patterns commonly described as symptom trajectories. PURPOSEThis study aimed to investigate the association between different amounts of physical activity and sedentary behavior and the trajectory of LBP, in people with a lifetime history of LBP. STUDY DESIGNThe study involved a secondary analysis of observational longitudinal data collected from the AUstralian Twin low BACK pain (AUTBACK) study. METHODSA total of 329 individual twins met the inclusion criteria for analysis. Latent Class Growth Analysis was used to identify distinct patterns of LBP and select the primary outcome (probability of having a severe LBP trajectory, 0%–100%). Linear regression models were used to investigate the association between different amounts of physical activity or sedentary behavior at baseline, and the probability of having a severe LBP trajectory. Results were expressed as β coefficients and 95% confidence intervals (CI). RESULTSModerate-to-vigorous intensity physical activity was significantly associated with the probability of having a severe LBP trajectory (unadjusted β -0.0276; 95%CI -0.0456 to -0.0097, p=.003). For every 1-minute increase in moderate-to-vigorous intensity physical activity per week, there was a 2.8%-point reduction in a participant's probability of having a severe LBP trajectory. No significant associations were identified between sedentary behavior or light intensity physical activity, and the probability of having a severe LBP trajectory. CONCLUSIONSIn people with a lifetime history of LBP, engagement in higher volumes of moderate to vigorous intensity physical activity at baseline was associated with a lower probability of developing a severe trajectory of LBP over 1 year.

Big Five personality traits and illicit drug use: Specificity in trait-drug associations.

High neuroticism, low agreeableness, and low conscientiousness are consistent correlates of drug use, though such patterns may be due to common familial influences rather than effects of personality per se. The present study aimed to explore associations of Big Five traits with various forms of drug use independent of confounding familial influences by leveraging differences within twin pairs to identify potentially causal (i.e., within-pair) effects of personality on use. 980 same-sex twin pairs from the Australian Twin Registry Cohort III (Mage = 31.70, 71% female) were interviewed regarding lifetime (mis)use of cannabis, cocaine/crack, prescription and illicit stimulants, prescription and illicit opioids, sedatives, hallucinogens, dissociatives, inhalants, and solvents, and completed a Big Five inventory. Co-twin control analyses predicted the use of each drug from all traits simultaneously. Individual-level analyses generally showed the expected associations of neuroticism, agreeableness, and conscientiousness with drug use. Familial effects were also somewhat generalized: high neuroticism, high openness to experience, and low agreeableness were associated with the use of several drug types. More specificity emerged for within-pair effects. High neuroticism was associated with prescription drug misuse; high extraversion was associated with cocaine/crack and stimulant use; high openness to experience was associated with cannabis use; low agreeableness was associated with cocaine/crack use and illicit opioid use; and no within-pair effects emerged for conscientiousness. Trait associations common across drugs may be primarily attributable to familial effects. There appears to be more drug-specific influence of personality on use with respect to potentially causal within-pair effects. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Establishing conversion of the 16-item Informant Questionnaire on Cognitive Decline in the Elderly scores into interval-level data across multiple samples using Rasch methodology.

The 16-item Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE-16) is a well-validated and widely-used measure of cognitive changes (CCs) among older adults. This study aimed to use Rasch methodology to establish psychometric properties of the IQCODE-16 and validate the existing ordinal-to-interval transformation algorithms across multiple large samples. A Partial Credit Rasch model was employed to examine psychometric properties of the IQCODE-16 using data (n=918) from two longitudinal studies of participants aged 57-99 years: the Older Australian Twins Study (n=450) and the Canberra Longitudinal Study (n=468), and reusing the Sydney Memory and Ageing Study (MAS) sample (n=400). Initial analyses indicated good reliability for the IQCODE-16 (Person Separation Index range: 0.82-0.90). However, local dependency was identified between items, with several items showing misfit to the model. Replicating the existing Rasch solution could not reproduce the best Rasch model fit for all samples. Combining locally dependent items into three testlets resolved all misfit and local dependency issues and resulted in the best Rasch model fit for all samples with evidence of unidimensionality, strong reliability, and invariance across person factors. Accordingly, new ordinal-to-interval transformation algorithms were produced to convert the IQCODE-16 ordinal scores into interval data to improve the accuracy of its scores. The findings of this study support the reliability and validity of the IQCODE-16 in measuring CCs among older adults. New ordinal-to-interval conversion tables generated using samples from multiple independent datasets are more generalizable and can be used to enhance the precision of the IQCODE-16 without changing its original format. An easy-to-use converter has been made available for clinical and research use.

Genetic and environmental influences on fruit and vegetable consumption and depression in older adults

BackgroundPrior work suggests that higher fruit and vegetable consumption may protect against depression in older adults. Better understanding of the influence of genetic and environmental factors on fruit and vegetable intakes may lead to the design of more effective dietary strategies to increase intakes. In turn this may reduce the occurrence of depression in older adults.ObjectivesThe primary aim of this study is to estimate the genetic and environmental influences on the consumption of fruit and vegetables in older adults. The secondary aim is an exploratory analysis into possible shared genetic influences on fruit and vegetable intakes and depression.MethodsAnalysis of observational data from 374 twins (67.1% female; 208 monozygotic (MZ); 166 dizygotic (DZ)) aged ≥ 65 years drawn from the Older Australian Twins Study. Dietary data were obtained using a validated food frequency questionnaire and depressive symptoms were measured using the 15-item short form Geriatric Depression Scale. The contribution of genetic and environmental influences on fruit and vegetable intake were estimated by comparing MZ and DZ twin intakes using structural equation modelling. A tri-variate twin model was used to estimate the genetic and environmental correlation between total fruit and vegetable intakes and depression.ResultsIn this study, vegetable intake was moderately influenced by genetics (0.39 95%CI 0.22, 0.54). Heritability was highest for brassica vegetables (0.40 95%CI 0.24, 0.54). Overall fruit intake was not significantly heritable. No significant genetic correlations were detected between fruit and vegetable intake and depressive symptoms.ConclusionsVegetable consumption, particularly bitter tasting brassica vegetables, was significantly influenced by genetics, although environmental influences were also apparent. Consumption of fruit was only influenced by the environment, with no genetic influence detected, suggesting strategies targeting the food environment may be particularly effective for encouraging fruit consumption.