Tessa L. Cutler

Understanding why children die in high-income countries

Many factors affect child and adolescent mortality in high-income countries. These factors can be conceptualised within four domains-intrinsic (biological and psychological) factors, the physical environment, the social environment, and service delivery. The most prominent factors are socioeconomic gradients, although the mechanisms through which they exert their effects are complex, affect all four domains, and are often poorly understood. Although some contributing factors are relatively fixed--including a childs sex, age, ethnic origin, and genetics, some parental characteristics, and environmental conditions--others might be amenable to interventions that could lessen risks and help to prevent future child deaths. We give several examples of health service features that could affect child survival, along with interventions, such as changes to the physical or social environment, which could affect upstream (distal) factors.

Indigenous Mortality (Revealed): The Invisible Illuminated

Inaccuracies in the identification of Indigenous status and the collection of and access to vital statistics data impede the strategic implementation of evidence-based public health initiatives to reduce avoidable deaths. The impact of colonization and subsequent government initiatives has been commonly observed among the Indigenous peoples of Australia, Canada, New Zealand, and the United States. The quality of Indigenous data that informs mortality statistics are similarly connected to these distal processes, which began with colonization. We discuss the methodological and technical challenges in measuring mortality for Indigenous populations within a historical and political context, and identify strategies for the accurate ascertainment and inclusion of Indigenous people in mortality statistics.

Why Accurate Knowledge of Zygosity is Important to Twins

All same-sex dizygotic (DZ) twins and approximately one-third of monozygotic (MZ) twin pairs have separate placentas, making it impossible to use the number of placentas to determine zygosity. Zygosity determination is further complicated because incorrect assumptions are often made, such as that only DZ pairs have two placentas and that all MZ pairs are phenotypically identical. These assumptions, by twins, their families and health professionals, along with the lack of universal zygosity testing for same-sex twins, has led to confusion within the twin community, yet little research has been conducted with twins about their understanding and assumptions about zygosity. We aimed to explore and quantify understanding and assumptions about zygosity using twins attending an Australian twin festival. We recruited 91 twin pairs younger than 18 years of age and their parents, and 30 adult twin pairs who were all uncertain of their zygosity, to complete one pen and paper questionnaire and one online questionnaire about their assumed zygosity, reasons for their assumptions and the importance of accurate zygosity knowledge. Responses were compared with their true zygosity measured using a genetic test. We found a substantial proportion of parents and twins had been misinformed by their own parents or medical professionals, and that knowledge of their true zygosity status provided peace of mind and positive emotional responses. For these reasons we propose universal zygosity testing of same-sex twins as early in life as possible and an increase in education of medical professionals, twins and families of twins about zygosity issues.

Zygosity testing should be encouraged for all same-sex twins: FOR: A genetic test is essential to determine zygosity.

FOR: A genetic test is essential to determine zygosity J.M. CRAIG, Group Leader, Early Life Epigenetics N.L. SEGAL, Director, Twin Studies Center M.P. UMSTAD, Director of Maternity Services T.L. CUTLER, Research Assistant L.A. KEOGH, Senior Lecturer, Centre for Health Equity J.L. HOPPER, Director, Australian Twin Registry M. RANKIN, Chairperson J. DENTON, Director CATHERINE A. DEROM, Scientific Director of the East Flanders Prospective Survey A. SUMATHIPALA J.R. HARRIS Professor on behalf of the International Society for Twin Studies (ISTS) and the International Council of Multiple Birth Organisations (ICOMBO)

Genetic and environmental influences on adult human height across birth cohorts from 1886 to 1994

Human height variation is determined by genetic and environmental factors, but it remains unclear whether their influences differ across birth-year cohorts. We conducted an individual-based pooled analysis of 40 twin cohorts including 143,390 complete twin pairs born 1886–1994. Although genetic variance showed a generally increasing trend across the birth-year cohorts, heritability estimates (0.69-0.84 in men and 0.53-0.78 in women) did not present any clear pattern of secular changes. Comparing geographic-cultural regions (Europe, North America and Australia, and East Asia), total height variance was greatest in North America and Australia and lowest in East Asia, but no clear pattern in the heritability estimates across the birth-year cohorts emerged. Our findings do not support the hypothesis that heritability of height is lower in populations with low living standards than in affluent populations, nor that heritability of height will increase within a population as living standards improve. DOI: http://dx.doi.org/10.7554/eLife.20320.001

Twin's Birth-Order Differences in Height and Body Mass Index From Birth to Old Age: A Pooled Study of 26 Twin Cohorts Participating in the CODATwins Project

We analyzed birth order differences in means and variances of height and body mass index (BMI) in monozygotic (MZ) and dizygotic (DZ) twins from infancy to old age. The data were derived from the international CODATwins database. The total number of height and BMI measures from 0.5 to 79.5 years of age was 397,466. As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood. After adjusting the results for birth weight, the birth order differences decreased and were no longer statistically significant. First-born twins had greater BMI than the second-born twins over childhood and adolescence. After adjusting the results for birth weight, birth order was still associated with BMI until 12 years of age. No interaction effect between birth order and zygosity was found. Only limited evidence was found that birth order influenced variances of height or BMI. The results were similar among boys and girls and also in MZ and DZ twins. Overall, the differences in height and BMI between first- and second-born twins were modest even in early childhood, while adjustment for birth weight reduced the birth order differences but did not remove them for BMI.

Twin's Birth-Order Differences in Height and Body Mass Index From Birth to Old Age: A Pooled Study of 26 Twin Cohorts Participating in the CODATwins Project.

We analyzed birth order differences in means and variances of height and body mass index (BMI) in monozygotic (MZ) and dizygotic (DZ) twins from infancy to old age. The data were derived from the international CODATwins database. The total number of height and BMI measures from 0.5 to 79.5 years of age was 397,466. As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood. After adjusting the results for birth weight, the birth order differences decreased and were no longer statistically significant. First-born twins had greater BMI than the second-born twins over childhood and adolescence. After adjusting the results for birth weight, birth order was still associated with BMI until 12 years of age. No interaction effect between birth order and zygosity was found. Only limited evidence was found that birth order influenced variances of height or BMI. The results were similar among boys and girls and also in MZ and DZ twins. Overall, the differences in height and BMI between first- and second-born twins were modest even in early childhood, while adjustment for birth weight reduced the birth order differences but did not remove them for BMI.

Association of current and former smoking with body mass index: A study of smoking discordant twin pairs from 21 twin cohorts

Background Smokers tend to weigh less than never smokers, while successful quitting leads to an increase in body weight. Because smokers and non-smokers may differ in genetic and environmental family background, we analysed data from twin pairs in which the co-twins differed by their smoking behaviour to evaluate if the association between smoking and body mass index (BMI) remains after controlling for family background. Methods and findings The international CODATwins database includes information on smoking and BMI measured between 1960 and 2012 from 156,593 twin individuals 18–69 years of age. Individual-based data (230,378 measurements) and data of smoking discordant twin pairs (altogether 30,014 pairwise measurements, 36% from monozygotic [MZ] pairs) were analysed with linear fixed-effects regression models by 10-year periods. In MZ pairs, the smoking co-twin had, on average, 0.57 kg/m2 lower BMI in men (95% confidence interval (CI): 0.49, 0.70) and 0.65 kg/m2 lower BMI in women (95% CI: 0.52, 0.79) than the never smoking co-twin. Former smokers had 0.70 kg/m2 higher BMI among men (95% CI: 0.63, 0.78) and 0.62 kg/m2 higher BMI among women (95% CI: 0.51, 0.73) than their currently smoking MZ co-twins. Little difference in BMI was observed when comparing former smoking co-twins with their never smoking MZ co-twins (0.13 kg/m2, 95% CI 0.04, 0.23 among men; -0.04 kg/m2, 95% CI -0.16, 0.09 among women). The associations were similar within dizygotic pairs and when analysing twins as individuals. The observed series of cross-sectional associations were independent of sex, age, and measurement decade. Conclusions Smoking is associated with lower BMI and smoking cessation with higher BMI. However, the net effect of smoking and subsequent cessation on weight development appears to be minimal, i.e. never more than an average of 0.7 kg/m2.

Birth size and gestational age in opposite-sex twins as compared to same-sex twins : An individual-based pooled analysis of 21 cohorts

It is well established that boys are born heavier and longer than girls, but it remains unclear whether birth size in twins is affected by the sex of their co-twin. We conducted an individual-based pooled analysis of 21 twin cohorts in 15 countries derived from the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), including 67,850 dizygotic twin individuals. Linear regression analyses showed that boys having a co-twin sister were, on average, 31 g (95% CI 18 to 45) heavier and 0.16 cm (95% CI 0.045 to 0.274) longer than those with a co-twin brother. In girls, birth size was not associated (5 g birth weight; 95% CI −8 to −18 and −0.089 cm birth length; 95% CI −0.202 to 0.025) with the sex of the co-twin. Gestational age was slightly shorter in boy-boy pairs than in boy-girl and girl-girl pairs. When birth size was standardized by gestational age, the magnitude of the associations was attenuated in boys, particularly for birth weight. In conclusion, boys with a co-twin sister are heavier and longer at birth than those with a co-twin brother. However, these differences are modest and partly explained by a longer gestation in the presence of a co-twin sister.

How ‘mental health smart’ are you? Analysis of responses to an Australian Broadcasting Corporation News website quiz

ABSTRACT Background: In Australia, 7.3 million people aged between 16 and 85 years of age will have a mental disorder during their lifetime and mental health knowledge can improve their long-term outcomes. Objective: This research examines the knowledge that the Australian public has about mental health and its associations with mental health training, personal experience, age and gender. Method: Data analyses were conducted on 16,783 (64% female) completed ‘How “mental health smart” are you?’ questionnaires from the Australian Broadcasting Corporation News website. Descriptive analyses were conducted, including examination of proportions of correct responses and multivariate logistic regression. Results: The descriptive analyses showed knowledge about depression was highest, while knowledge about anxiety and psychosis were lowest. People who reported experience with their own or friends/family mental health problems had higher odds of answering correctly, as did people who had completed any mental health training. Discussion: Insights in these areas could be used to target future interventions, including increased public awareness campaigns for mental illnesses with lower public health knowledge such as psychosis and anxiety. The results of this study support an increase in the availability of mental health training such as the Mental Health First Aid course to the Australian public.