Exploring the Association Between Help-Seeking Intentions and Suicidal Ideation in Australian Adult Men.

Background: Men account for three-quarters of suicide deaths in Australia. Self-reliant masculine norms may act as barriers to men's help-seeking and contribute to suicidal ideation. Men who seek help may be less likely to experience suicidal ideation. Aim: We evaluated the association between help-seeking intentions and suicidal ideation in Australian adult men using data from Wave 2 of the Australian Longitudinal Study on Male Health (Ten to Men). Method: Using scores on the General Help-Seeking Questionnaire, we explored the association between informal help-seeking intentions (e.g., friend, family), formal help-seeking intentions (e.g., psychologist), overall help-seeking intentions (all sources), and new-onset suicidal ideation. We conducted logistic regression analyses using a sample of 7,828 men aged 18-60 years. Results: Increased overall help-seeking intentions and informal help-seeking intentions were significantly associated with lower odds of new-onset suicidal ideation, whereas formal help-seeking intentions were not significantly associated. Limitations: The cross-sectional design limits inferences about causality. Conclusion: Men who have greater informal help-seeking intentions may be less likely to experience a new onset of suicidal ideation; however, more longitudinal research is needed.

Exercise and Artery Function in Twins: Sex Differences in a Cross-Over Trial.

BACKGROUND: Physical activity reduces cardiovascular risk, partly via direct effects on the arterial wall. We hypothesized that vascular function responses would be modality-specific, sex-dependent, and express a high degree of heritability. METHODS: We recruited 90 same-sex twins (31 monozygotic, 14 dizygotic dizygotic pairs; 25.8±6.0 years) and randomized 70 (25 monozygotic, 10 dizygotic) to complete, as pairs, 3 months each of resistance and endurance training, separated by a 3-month washout. RESULTS: Brachial artery flow-mediated (FMD%) and glyceryl-trinitrate induced dilation (GTN%) both increased following endurance (FMD%: ∆1.46%, P<0.001; GTN%: ∆1.76%, P=0.004) and resistance (FMD%: ∆1.73%, P<0.001; GTN%: ∆1.68%, P=0.045). About one-third of participants failed to respond to one or other mode; 10% failed to respond to both for FMD% (17% for GTN%). FMD% and GTN% increased significantly in response to both resistance and endurance in females (P<0.05), but not males. Twin analysis revealed that responses to both FMD% and GTN% with exercise training for both modalities were dependent on factors shared by monozygotic pairs and that a large contribution from genetic effects is unlikely. CONCLUSIONS: Our findings indicate that both endurance and resistance can enhance vascular function and that responses in females were more marked. Most individuals respond to one or other form of training, with few unresponsive to both; a finding that has implications for optimizing exercise-based approaches for individualized benefit. Focusing on characteristics of exercise prescription may be more important than the impact of distinct candidate genes when considering exercise as a form of vascular medicine. REGISTRATION: URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=371222; Unique identifier: ACTRN 12616001095459.

Computed tomography scan radiation and brain cancer incidence.

BACKGROUND: Computed tomography (CT) scans make substantial contributions to low-dose ionizing radiation exposures, raising concerns about excess cancers caused by diagnostic radiation. METHODS: Deidentified medicare records for all Australians aged 0-19 years between 1985-2005 were linked to national death and cancer registrations to 2012. The National Cancer Institute CT program was used to estimate radiation doses to the brain from CT exposures in 1985-2005, Poisson regression was used to model the dependence of brain cancer incidence on brain radiation dose, which lagged by 2 years to minimize reverse causation bias. RESULTS: Of 10 524 842 young Australians, 611 544 were CT-exposed before the age of 20 years, with a mean cumulative brain dose of 44 milligrays (mGy) at an average follow-up of 13.5 years after the 2-year lag period. 4472 were diagnosed with brain cancer, of whom only 237 had been CT-exposed. Brain cancer incidence increased with radiation dose to the brain, with an excess relative risk of 0.8 (95% CI 0.57-1.06) per 100 mGy. Approximately 6391 (95% CI 5255, 8155) persons would need to be exposed to cause 1 extra brain cancer. CONCLUSIONS: For brain tumors that follow CT exposures in childhood by more than 2 years, we estimate that 40% (95% CI 29%-50%) are attributable to CT Radiation and not due to reverse causation. However, because of relatively low rates of CT exposure in Australia, only 3.7% (95% CI 2.3%-5.4%) of all brain cancers are attributable to CT scans. The population-attributable fraction will be greater in countries with higher rates of pediatric scanning.

Evaluating the Effectiveness of Components of National Suicide Prevention Strategies.

Background: National suicide prevention strategies support development of suicide prevention activities and their evaluation. Aims: To describe components included in national suicide prevention strategies and analyze the potential contribution of individual components to reduce suicide rates. Method: We conducted a narrative review and statistical analysis of national suicide prevention strategies. The narrative review was based on a framework of 12 components and included 29 countries (14 lower middle-income countries [LMICs] and 15 high-income countries [HICs]) with a national suicide prevention strategy. The statistical analyses covered suicide mortality data for 24 countries with a national strategy (9 LMICs and 15 HICs). Results: The number of components adopted in national strategies ranged from 4 to 11, and training and education were included in 96.5% of strategies. Estimated period effects for total suicide rates in individual countries ranged from a significant decrease in the yearly suicide rate (RR = 0.80; 95% CI 0.69-0.93) to a significant increase (RR = 1.12; 95% CI 1.05-1.19). There were no changes in suicide mortality associated with individual components of national strategies. Limitations: The limitations of existing suicide mortality data apply to our study. Conclusion: Further detailed evaluations will help identify the specific contribution of individual components to the impact national strategies. Until then, countries should be encouraged to implement and evaluate comprehensive national suicide prevention strategies.

Evidence for ethnicity and location as regulators of the newborn blood metabolome: a monozygous twin study.

Introduction: Monochorionic, diamniotic (MCDA) monozygotic twins share nearly all genetic variation and a common placenta in utero. Despite this, MCDA twins are often discordant for a range of common phenotypes, including early growth and birth weight. As such, MCDA twins represent a unique model to explore variation in early growth attributable primarily to in utero environmental factors. Methods: MCDA twins with a range of within-pair birth weight discordance were sampled from the peri/postnatal epigenetic twin study (PETS, Melbourne; n = 26 pairs), Beijing twin study (BTS, Beijing; n = 25), and the Chongqing longitudinal twin study (LoTiS, Chongqing; n = 22). All PETS participants were of European-Australian ancestry, while all Chinese participants had Han ancestry. The average of the birth weight difference between the larger and smaller co-twins for all twin pairs was determined and metabolomic profiles of amino acids, TCA cycle intermediates, fatty acids, organic acids, and their derivatives generated from cord blood plasma by gas chromatograph mass spectrometry. Within and between co-twin pair analyses were performed to identify metabolites specifically associated with discordance in birth weight. Multivariable regression and pathway enrichment analyses between different regions were performed to evaluate the geographical effects on the metabolism of MCDA twin pairs. Results: PETS twins showed a markedly different metabolic profile at birth compared to the two Chinese samples. Within-pair analysis revealed an association of glutathione, creatinine, and levulinic acid with birth weight discordance. Caffeine, phenylalanine, and several saturated fatty acid levels were uniquely elevated in PETS twins and were associated with maternal BMI and average within pair birth weight, in addition to birth weight discordance. LoTiS twins had higher levels of glutathione, tyrosine, and gamma-linolenic acid relative to PETS and BTS twins, potentially associated with eating habits. Conclusion: This study highlights the potential role of underlying genetic variation (shared by MZ twins), in utero (non-shared by MZ twins) and location-specific (shared by MZ twins) environmental factors, in regulating the cord blood metabolome of uncomplicated MCDA twins. Future research is needed to unravel these complex relationships that may play a key role in phenotypic metabolic alterations of twins independent of genetic diversity.

Cohort profile: The Australian Paediatric Exposure to Radiation Cohort (Aust-PERC).

Although the carcinogenic effects of high-dose radiation are well-established, the risks at low doses, such as from diagnostic X-rays, are less well understood. Children are susceptible to radiation induced cancers, and in the last decade, several cohort studies have reported increased cancer risks following computed tomography (CT) scans in childhood. However, cohort studies can be limited by insufficient follow-up, indication bias, reverse causation, or by lack of organ doses from CT scans or other exposures. Aust-PERC is a retrospective cohort designed to study the effects of low-dose medical radiation exposure, primarily from CT scans, in young Australians. The cohort was ascertained using deidentified billing records from patients who were aged 0-19 years while enrolled in Medicare (Australia's universal healthcare system) between 1985 and 2005. All procedures billed to Medicare in this age/time window that involved low-dose radiation were identified, and persons without such procedures were flagged as unexposed. The Aust-PERC cohort has been linked, using confidential personal identifiers, to the Australian Cancer Database and the National Death Index, on two occasions (to Dec. 2007 and Dec. 2012) by the responsible government agency (Australian Institute of Health and Welfare). Deidentified Medicare service records of all radiological procedures including CT scans, nuclear medicine (NM) scans and fluoroscopy and plain X-ray procedures have been available to derive estimated radiation doses in the cohort. Records of other medical and surgical procedures, together with demographic and socioeconomic variables are being used in analyses to assess biases arising from reverse causation and confounding. After excluding patients with errant records, 11 802 846 persons remained in the baseline cohort, with an average follow-up time of 22.3 years to December 2012. There were 275 489 patients exposed to diagnostic nuclear medicine scans and 688 363 patients exposed to CT scans before age 20 and before cancer diagnosis. Between 1 January 1985 and 31 December 2012, there were 105 124 deaths and 103 505 incident cancers. Dose-response analyses based on the relevant organ doses are underway for individual cancers, and we plan to extend the follow-up for another 8 years to Dec 2020. Analyses using this very large Aust-PERC cohort, with extended follow-up, will help to resolve international uncertainties about the causal role of diagnostic medical radiation as a cause of cancer.

Three trajectories of gestational weight gain identified in an Australian twin study.

OBJECTIVES: Gestational weight gain (GWG) has been associated with maternal and child health outcomes, but knowledge of appropriate GWG for twin gestations is limited. STUDY DESIGN: The Peri/Postnatal Epigenetic Twins Study is a prospective twin cohort study of 250 women and their twin children in Melbourne, Australia. We modeled trajectories of GWG using group-based growth modeling and compared these trajectories to GWG categories (within, above, or below current GWG recommendations for twin pregnancy). We fitted robust linear and Poisson regression models to assess associations of maternal pre-pregnancy and gestational exposures with risk of gaining weight outside the recommendations. RESULTS: Of the 250 women enrolled in the PETS, GWG measures were available for 172 women. Forty-seven percent of women had GWG within the current recommendations. We identified three GWG trajectories - 23.6% of women had low GWG throughout pregnancy, 34.5% had average GWG throughout pregnancy, and 42.0% had average initial GWG, followed by high GWG from trimester two until delivery. Gestational diabetes mellitus (GDM) was associated with increased risk of inadequate GWG (RR: 2.40, 95%CI: 1.53, 3.75). Pre-pregnancy obesity (RR: 1.88, 95%CI: 1.09, 3.26) and hypertensive disorders of pregnancy (RR: 2.64, 95%CI: 1.20, 5.81) were associated with increased risk of excessive GWG. CONCLUSIONS: More than half of the women in the PETS did not meet the current GWG recommendations. Women with GDM or hypertensive disorders were more likely to gain weight outside these guidelines. More research is needed to establish comprehensive guidelines for twin pregnancies.

Studies of Twin Responses to Understand Exercise THerapy (STRUETH): cerebrovascular function.

We studied monozygotic (MZ) and dizygotic (DZ) twin pairs following resistance (RES) and endurance (END) training to assess genetic and environmental contributions to cerebrovascular function. Cerebrovascular function (rest, autoregulation, hypercapnia, exercise) was assessed in 86 healthy same-sex MZ (30 pairs) and DZ (13 pairs) twins, who underwent 3 months of END and RES. Carbon dioxide ( PETCO2${P_{{\rm{ETC}}{{\rm{O}}_{\rm{2}}}}}$ ), mean arterial pressure (MAP) and middle cerebral artery velocity (MCAv) were measured and MCAv resistance (MCACVRi ) was calculated. Resting MCAv reduced by -2.8 cm/s following RES (P = 0.024), with no change following END (-0.3 cm/s, P = 0.758). Change in MCACVRi following RES was +0.11 mmHg/cm/s (P < 0.001), which was significantly greater than END (+0.02 mmHg/cm/s, P = 0.030). MAP also increased following RES (+4 mmHg, P = 0.010), but not END (+1 mmHg, P = 0.518). No changes were apparent in PETCO2${P_{{\rm{ETC}}{{\rm{O}}_{\rm{2}}}}}$ . At rest, positive response rates following RES ranged from 27 to 71% and from 40 to 64% following END. Intraclass correlations between twins were moderate for most variables at baseline. In response to training, only MZ pairs were significantly correlated for a change in MCAv (P = 0.005) and low frequency phase (P = 0.047) following RES.This study is the first to compare cerebrovascular function following RES and END in MZ and DZ twins. Most individuals who did not respond to one modality were able to respond by switching modality, and baseline heritability estimates were higher than training response. Exercise professionals should therefore consider modality and environmental factors when optimising interventions. KEY POINTS: Characterising individual responses to resistance and endurance exercise training can inform optimal strategies for exercise prescription. This study utilised monozygotic and dizygotic twins in a randomised cross-over study to determine individual responsiveness to different modalities of exercise training. The influence of environment vs. genetics on cerebrovascular responses to training was determined. It is apparent that individuals respond differently to distinct exercise stimuli and that switching modality may be a beneficial way to obtain positive responses in cerebrovascular function. This study has implications for improving individualised exercise prescription to maintain or improve cerebrovascular structure and function.

Gestational weight gain is associated with childhood height, weight and BMI in the Peri/Postnatal Epigenetic Twins Study.

Multifetal pregnancies are at risk of adverse maternal, neonatal and long-term health outcomes, and gestational weight gain (GWG) is a potentially modifiable risk factor for several of these. However, studies assessing the associations of GWG with long-term health in twins are rare, and studies which do assess these associations in twins often do not account for gestational age. Since longer gestations are likely to lead to larger GWG and lower risk of adverse outcomes, adjusting for gestational age is necessary to better understand the association of GWG with twin health outcomes. We aimed to explore long-term associations of GWG-for-gestational-age with twin anthropometric measures. The Peri/Postnatal Epigenetic Twins Study (PETS) is a prospective cohort study, which recruited women pregnant with twins from 2007 to 2009. Twins were followed-up at 18 months and 6 years of age. GWG-for-gestational-age z-scores were calculated from pre-pregnancy weight and weight at delivery. We fitted regression models to assess associations of GWG with twin weight, height and BMI at birth, 18 months, and 6 years. Of the 250 women in the PETS, 172 had GWG measured throughout pregnancy. Overall, higher GWG-for-gestational-age z-scores were associated with higher birthweight (ß: 0.32 z-scores, 95% Confidence Interval (95% CI): 0.19, 0.45), BMI (ß: 0.29 z-scores, 95% CI: 0.14, 0.43) and length (ß: 0.27 z-scores, 95% CI: 0.09, 0.45). However, these associations were not observed at 18 months or 6 years of age. GWG was associated with twin length, weight and BMI at birth but not during childhood. Further research is needed to determine the long-term effects of GWG on twin health outcomes.

Left Ventricular Adaptation to Exercise Training via Magnetic Resonance Imaging: Studies of Twin Responses to Understand Exercise THerapy.

PURPOSE: Changes in left ventricular mass (LVM) and end-diastolic volume (EDV) in response to exercise training are important determinants of functional capacity in health and disease, but the impact of different exercise modalities remains unclear. METHODS: Using a randomized crossover design we studied the impact of resistance (RES) and endurance (END) training using cardiac magnetic resonance imaging in previously untrained monozygotic (MZ) and dizygotic (DZ) twin pairs (n = 72; 22 MZ pairs, 14 DZ same-sex pairs; 26.1 ± 5.4 yr). Twins, as pairs, undertook 3 months of RES and 3 months of END training (order randomized), separated by a 3-month washout. RESULTS: Group results revealed that END increased LVM (P < 0.001) and EDV (P = 0.007), whereas RES did not (P > 0.05). A higher proportion of individuals responded to END than RES for LVM (72% vs 38%, P < 0.001) and EDV (67% vs 40%, P = 0.003). Baseline cross-sectional intraclass correlations were higher for MZ than DZ twin pairs for all variables (e.g., LVM heritability = 0.42), but no significant correlations were apparent between pairs for change in any variable in response to either RES or END (P > 0.05). CONCLUSIONS: Our findings indicate that cardiac adaptation in response to exercise is modality-specific and that low responders to one mode of exercise can be high responders to an alternative. Heritability estimates based on cross-sectional data, which suggested a genetic contribution to LVM, do not accord with estimates based on training effects, which indicated limited genetic impact on adaptation in this 3-month study of exercise training. This study has implications for understanding the physiological and health impacts of typically used exercise modalities on cardiac adaptation in previously untrained individuals.

Thoughts of suicide or self-harm among Australian healthcare workers during the COVID-19 pandemic.

OBJECTIVE: To identify the prevalence and predictors of (a) thoughts of suicide or self-harm among healthcare workers during the COVID-19 pandemic and (b) help-seeking among those healthcare workers with thoughts of suicide or self-harm. METHOD: Analysis of data from the Australian COVID-19 Frontline Healthcare Workers Study, an online survey of healthcare workers conducted during the second wave of the COVID-19 pandemic in Australia. Outcomes of interest were thoughts of suicide or self-harm as measured through the Patient Health Questionnaire for depression and help-seeking behaviours. RESULTS: Overall, 819 (10.5%) of 7795 healthcare workers reported thoughts of suicide or self-harm over a 2-week period. Healthcare workers with these thoughts experienced higher rates of depression, anxiety, post-traumatic stress disorder and burnout than their peers. In multivariable models, the odds of suicide or self-harm thoughts were higher among workers who had friends or family infected with COVID-19 (odds ratio = 1.24, 95% confidence interval = [1.06, 1.47]), were living alone (odds ratio = 1.32, 95% confidence interval = [1.06, 1.64]), younger (⩽30 years cf. >50 years; odds ratio = 1.70, 95% confidence interval = 1.36-2.13), male (odds ratio = 1.81, 95% confidence interval = [1.49, 2.20]), had increased alcohol use (odds ratio = 1.58, 95% confidence interval = [1.35, 1.86]), poor physical health (odds ratio = 1.62, 95% confidence interval = [1.36, 1.92]), increased income worries (odds ratio = 1.81, 95% confidence interval = [1.54, 2.12]) or prior mental illness (odds ratio = 3.27, 95% confidence interval = [2.80, 3.82]). Having dependent children was protective (odds ratio = 0.75, 95% confidence interval = [0.61, 0.92]). Fewer than half (388/819) of the healthcare workers who reported thoughts of suicide or self-harm sought professional support. Healthcare workers with thoughts of suicide or self-harm were more likely to seek support if they were younger (⩽30 years cf. >50 years; odds ratio = 1.78, 95% confidence interval = [1.13, 2.82]) or had prior mental health concerns (odds ratio = 4.47, 95% confidence interval = [3.25, 6.14]). CONCLUSION: One in 10 Australian healthcare workers reported thoughts of suicide or self-harm during the pandemic, with certain groups being more vulnerable. Most healthcare workers with thoughts of suicide or self-harm did not seek professional help. Strong and sustained action to protect the safety of healthcare workers, and provide meaningful support, is urgently needed.

Birthweight-for-gestational-age z-scores are associated with early childhood cardiometabolic health in the Peri/Postnatal Epigenetic Twin Study.

Birthweight has been consistently related to risk of cardiometabolic disorders in later life. Twins are at higher risk of low birthweight than singletons, so understanding the links between birthweight and cardiometabolic health may be particularly important for twins. However, evidence for the association of birthweight with childhood markers of cardiometabolic health in twins is currently lacking. Previous studies have often failed to appropriately adjust for gestational age or fully implement twin regression models. Therefore, we aimed to evaluate the association of birthweight-for-gestational-age z-scores with childhood cardiometabolic health in twins, using within-between regression models. The Peri/Postnatal Epigenetic Twins Study is a Melbourne-based prospective cohort study of 250 twin pairs. Birthweight was recorded at delivery, and childhood anthropometric measures were taken at 18-month and 6-year follow-up visits. Associations of birthweight with markers of cardiometabolic health were assessed at the individual, between- and within-pair level using linear regression with generalised estimating equations. Birthweight-for-gestational-age z-scores were associated with height, weight and BMI at 18 months and 6 years, but not with blood pressure (twins-as-individual SBP: ß = 0.15, 95% CI: -0.81, 1.11; twins-as-individual DBP: ß = 0.22, 95% CI: -0.34, 0.77). We found little evidence to indicate that the within-between models improved on the twins-as-individuals models. Birthweight was associated with childhood anthropometric measures, but not blood pressure, after appropriately adjusting for gestational age. These associations were consistent across the within-between and twins-as-individuals models. After adjusting for gestational age, results from the twins-as-individuals models are consistent with singleton studies, so these results can be applied to the general population.

Birthweight, gestational age and familial confounding in sex differences in infant mortality: a matched co-twin control study of Brazilian male-female twin pairs identified by population data linkage.

BACKGROUND: In infancy, males are at higher risk of dying than females. Birthweight and gestational age are potential confounders or mediators but are also familial and correlated, posing epidemiological challenges that can be addressed by studying male-female twin pairs. METHODS: We studied 28 558 male-female twin pairs born in Brazil between 2012 and 2016, by linking their birth and death records. Using a co-twin control study matched for gestational age and familial factors, we applied logistic regression with random effects (to account for paired data) to study the association between male sex and infant death, adjusting for: birthweight, within- and between-pair effects of birthweight, birth order and gestational age, including interactions. The main outcome was infant mortality (0-365 days) stratified by neonatal (early and late) and postneonatal deaths. RESULTS: Males were 100 g heavier and more at risk of infant death than their female co-twins before [odds ratio (OR) = 1.28, 95% confidence interval (CI): 1.11-1.49, P = 0.001] and after (OR = 1.60, 95% CI: 1.39-1.83, P <0.001) adjusting for birthweight and birth order. When adjusting for birthweight within-pair difference and mean separately, the OR attenuated to 1.40 (95% CI: 1.21-1.61, P <0.001), with evidence of familial confounding (likelihood ratio test, P <0.001). We found evidence of interaction (P = 0.001) between male sex and gestational age for early neonatal death. CONCLUSIONS: After matching for gestational age and familial factors by design and controlling for birthweight and birth order, males remain at greater risk of infant death than their female co-twins. Birthweight's role as a confounder can be partially explained by familial factors.

Pregnancy and birth characteristics of Aboriginal twins in two Australian states: a data linkage study.

INTRODUCTION: Perinatal outcomes for singleton pregnancies are poorer, on average, for Aboriginal people than non-Aboriginal people, but little is known about Aboriginal multifetal pregnancies. Yet multifetal pregnancies and births are often more complicated and have poorer outcomes than singleton pregnancies. We describe the pregnancies, births and perinatal outcomes for Aboriginal twins born in Western Australia (WA) and New South Wales (NSW) with comparisons to Aboriginal singletons in both states and to non-Aboriginal births in NSW. MATERIALS AND METHODS: Whole-population birth records and birth and death registrations were linked for all births during 2000-2013 (WA) and 2002-2008 (NSW). Hospital records and the WA Register of Developmental Anomalies - Cerebral Palsy were linked for all WA births and hospital records for a subset of NSW births. Descriptive statistics are reported for maternal and child demographics, maternal health, pregnancy complications, births and perinatal outcomes. RESULTS: Thirty-four thousand one hundred twenty-seven WA Aboriginal, 32,352 NSW Aboriginal and 601,233 NSW non-Aboriginal births were included. Pregnancy complications were more common among mothers of Aboriginal twins than Aboriginal singletons (e.g. 17% of mothers of WA twins had hypertension/pre-eclampsia/eclampsia vs 8% of mothers of singletons) but similar to mothers of NSW non-Aboriginal twins. Most Aboriginal twins were born in a principal referral, women's or large public hospital. The hospitals were often far from the mother's home (e.g. 31% of mothers of WA Aboriginal twins gave birth at hospitals located more than 3 h by road from their home). Outcomes were worse for Aboriginal liveborn twins than Aboriginal singletons and non-Aboriginal twins (e.g. 58% of NSW Aboriginal twins were preterm compared to 9% of Aboriginal singletons and 49% non-Aboriginal twins). CONCLUSIONS: Mothers of Aboriginal twins faced significant challenges during the pregnancy, birth and the postnatal period in hospital and, in addition to accessible specialist medical care, these mothers may need extra practical and psychosocial support throughout their journey.

Association of Adult Socioeconomic Status with Body Mass Index: A Within- and Between-Twin Study.

Adult socioeconomic status (SES) has been consistently associated with body mass index (BMI), but it is unclear whether it is linked to BMI independently of childhood SES or other potentially confounding factors. Twin studies can address this issue by implicitly controlling for childhood SES and unmeasured confounders. This co-twin control study used cross-sectional data from Twins Research Australia's Health and Lifestyle Questionnaire (N = 1918 twin pairs). We investigated whether adult SES, as measured by both the Index of Relative Socioeconomic Disadvantage (IRSD) and the Australian Socioeconomic Index 2006 (AUSEI06), was associated with BMI after controlling for factors shared by twins within a pair. The primary analysis was a linear mixed-effects model that estimated effects both within and between pairs. Between pairs, a 10-unit increase in AUSEI06 was associated with a 0.29 kg/m2 decrease in BMI (95% CI [-.42, -.17], p < .001), and a 1-decile increase in IRSD was associated with a 0.26 kg/m2 decrease in BMI (95% CI [-.35, -.17], p < .001). No association was observed within pairs. In conclusion, higher adult SES was associated with lower BMI between pairs, but no association was observed within pairs. Thus, the link between adult SES and BMI may be due to confounding factors common to twins within a pair.

Studies of Twin Responses to Understand Exercise Therapy (STRUETH): Body Composition.

PURPOSE: We studied individual variability in exercise responses in twins. We hypothesized that 1) endurance (END) training would reduce fat mass whereas resistance (RES) training would increase lean mass, 2) individuals who did not respond to one modality would respond to the other, and 3) cross-sectional heritability estimates would be higher than estimates based on training responses. METHODS: DXA was undertaken in 84 same-sex untrained twins (30 monozygotic [MZ], 12 dizygotic [DZ]). Participants underwent 3 months of END and RES training, separated by 3 months washout. Twins trained in pairs. RESULTS: RES (P < 0.001) and END (P = 0.002) increased lean mass, with a greater change in RES (P < 0.001). Similarly, RES (P = 0.04) and END (P = 0.006) decreased fat mass. Eighty-four percent of subjects responded positively to RES for lean mass and 58% to END (P < 0.001). For fat mass, RES and END induced 56% and 66% responder rates, respectively (P = 0.28). Cross-sectional intraclass correlations, used to assess the similarity in twin responses, were higher for MZ than DZ pairs for all variables. Following training, only MZ pairs were significantly correlated (P < 0.001) for change in lean mass to RES. CONCLUSION: To our knowledge, this study is the first to report individual responsiveness in body composition to both RES and END in the same subjects. Although RES and END induced favorable changes in fat mass, RES was superior for lean mass. The frequency of lean mass responders to RES exceeded that for END, whereas response rates for fat mass were similar. Cross-sectional heritability estimates were higher than training response estimates, and shared environment had the largest influence on changes in body composition. This study suggests that exercise professionals should consider modality and environmental factors when optimizing exercise interventions.

Conducting Clinical Trials in Twin Populations: A Review of Design, Analysis, Recruitment and Ethical Issues for Twin-Only Trials.

Although twins often participate in medical research, few clinical trials are conducted entirely in twin populations. The purpose of this review is to demonstrate the substantial benefits and address the key challenges of conducting clinical trials in twin populations, or 'twin-only trials'. We consider the unique design, analysis, recruitment and ethical issues that arise in such trials. In particular, we describe the different approaches available for randomizing twin pairs, highlight the similarity or correlation that exists between outcomes of twins, and discuss the impact of this correlation on sample size calculations and statistical analysis methods for estimating treatment effects. We also consider the role of both monozygotic and dizygotic twins for studying variation in outcomes, the factors that may affect recruitment of twins, and the ethics of conducting trials entirely in twin populations. The advantages and disadvantages of conducting twin-only trials are also discussed. Finally, we recommend that twin-only trials should be considered more often.

Ct Dosimetry for The Australian Cohort Data Linkage Study.

Children undergoing computed tomography (CT) scans have an increased risk of cancer in subsequent years, but it is unclear how much of the excess risk is due to reverse causation bias or confounding, rather than to causal effects of ionising radiation. An examination of the relationship between excess cancer risk and organ dose can help to resolve these uncertainties. Accordingly, we have estimated doses to 33 different organs arising from over 900 000 CT scans between 1985 and 2005 in our previously described cohort of almost 12 million Australians aged 0-19 years. We used a multi-tiered approach, starting with Medicare billing details for government-funded scans. We reconstructed technical parameters from national surveys, clinical protocols, regulator databases and peer-reviewed literature to estimate almost 28 000 000 individual organ doses. Doses were age-dependent and tended to decrease over time due to technological improvements and optimisation.

Developmental origins of cardiometabolic health outcomes in twins: A systematic review and meta-analysis.

BACKGROUND AND AIMS: Studies of twins can reduce confounding and provide additional evidence about the causes of disease, due to within-pair matching for measured and unmeasured factors. Although findings from twin studies are typically applicable to the general population, few studies have taken full advantage of the twin design to explore the developmental origins of cardiometabolic health outcomes. We aimed to systematically review the evidence from twin studies and generate pooled estimates for the effects of early-life risk factors on later-life cardiometabolic health. METHODS AND RESULTS: An initial search was conducted in March 2018, with 55 studies of twins included in the review. Risk of bias was assessed using the Newcastle-Ottawa Scale, and eligible studies were included in a meta-analysis, where pooled estimates were calculated. Twenty-six studies analysed twins as individuals, and found that higher birthweight was associated with lower SBP (ß = -2.02 mmHg, 95%CI: -3.07, -0.97), higher BMI (ß = 0.52 kg/m2, 95%CI: 0.20, 0.84) and lower total cholesterol (ß = -0.07 mmol/L, 95%CI: -0.11, -0.04). However, no associations were reported in studies which adjusted for gestational age. Few of the included studies separated their analyses into within-pair and between-pair associations. CONCLUSIONS: Early-life risk factors were associated with cardiometabolic health outcomes in twin studies. However, many estimates from studies in this review were likely to have been confounded by gestational age, and few fully exploited the twin design to assess the developmental origins of cardiometabolic health outcomes.