Response to early literacy instruction in the United States, Australia, and Scandinavia A behavioral-genetic analysis

Abstract Genetic and environmental influences on early reading and spelling at the end of kindergarten and Grade 1 were compared across three twin samples tested in the United States, Australia, and Scandinavia. Proportions of variance due to genetic influences on kindergarten reading were estimated at .84 in Australia, .68 in the U.S., and .33 in Scandinavia. The effects of shared environment on kindergarten reading were estimated at .09 in Australia, .25 in the U.S., and .52 in Scandinavia. A similar pattern of genetic and environmental influences was obtained for kindergarten spelling. One year later when twins in all three samples had received formal literacy instruction for at least one full school year, heritability was similarly high across country, with estimated genetic influences varying between .79 and .83 for reading and between .62 and .79 for spelling. These findings indicate that the pattern of genetic and environmental influences on early reading and spelling development varies according to educational context, with genetic influence increasing as a function of increasing intensity of early instruction. Longitudinal analyses revealed genetic continuity for both reading and spelling between kindergarten and Grade 1 across country. However, a new genetic factor comes into play accounting for independent variance in reading at Grade 1 in the U.S. and Scandinavia, suggesting a change in genetic influences on reading. Implications for responseto-instruction are discussed. 4 Historically, and as late as 1800, more than 50% of the population in most western countries was illiterate. The opportunity to learn to read and write was a privilege, to a large extent determined by social-cultural conditions In this article, we continue to report on our International Longitudinal Twin Study (ILTS) of early language and literacy development The main purpose here was to compare genetic and environmental influences on early reading and spelling skills across three twin samples tested in the United States, Australia, and Scandinavia (i.e., Sweden and Norway) and across time of testing (i.e., kindergarten and Grade 1). Two questions are addressed: First, are there any differences in the pattern of genetic and environmental influences on early reading and spelling skills across country? Second, what are the changes in the pattern of genetic and environmental influences on reading and spelling from kindergarten to Grade 1? The general expectation is that the effects of environment on literacy skills should decrease and the genetic contribution increase as a function of intensity and consistency of instruction, across countries and time. This approach should also inform recent interest in response-to-intervention, or RTI, as a method to ascertain, define, and remediate 5 reading difficulties The ILTS has previously documented substantial effects of genes and relatively minor However, in a recent ILTS study of data collected near the end of kindergarten ), individual differences in reading and spelling skills were mainly 6 accounted for by genetic factors in a sample of Australian twins, with estimates of .91 and .84, respectively. In contrast, in a sample of U.S. twins from the state of Colorado, only approximately half of the variance in reading and spelling was accounted for by genetic influences, with the other half attributed to shared and non-shared environment. Although these country differences in genetic and environmental influences on individual differences in reading and spelling were not statistically significant with the available sample sizes, we hypothesized that the trends might be explained by country differences in educational practice. Compulsory school starts at around age five in both Australia and Colorado, but in New South Wales, Australian children enter a school system regulated by a state-wide curriculum mandating that at least 35% of a full school week (9 am to 3 pm, five days a week) should be devoted to language and literacy instruction. In contrast, in Colorado children attend kindergarten school for only 3-4 hours each day, and there is no state-mandated curriculum for teaching reading and spelling. One plausible explanation for the different pattern of genetic and environmental influences on reading and spelling in Australia and U.S. is that a state-wide curriculum emphasizing intense literacy instruction reduces the environmental range in the population, and thus, the amount of variance in reading and spelling skills that can be accounted for by environmental factors. Another explanation is that the greater intensity of instruction in NSW engages genetically-influenced learning processes earlier than in the US, resulting in a higher genetic contribution to overall variability. To further explore these hypotheses, the present study includes a sample of Scandinavian twins. In Scandinavia, compulsory school starts when the child is seven years old, that is, one to two years later compared to Australia and the U.S. Nevertheless, almost all children do attend kindergarten prior to compulsory attendance in Grade 1, but kindergarten curriculum in Sweden and Norway emphasizes social, emotional, and aesthetic development rather than early literacy acquisition. In this way, Scandinavia represents a population where environmental 7 variation outside of school might have a substantial impact on individual differences in kindergarten reading and spelling skills because there is no formal reading instruction in kindergarten. Instead, literacy socialization is mainly given informally at home. However, at seven years of age, in Grade 1, teaching reading and spelling is the target activity in school, and literacy instruction is guided by a master plan common to all schools in Sweden and Norway. This change from informal literacy teaching taking place at the children's home to a countrywide curriculum emphasizing formal reading and spelling instruction should reduce environmental range and increase the intensity of engagement. From kindergarten to Grade 1, we hypothesize, therefore, that the heritability of literacy skills increases and the importance of shared environment decreases in Scandinavia. To summarize, we hypothesize different contributions from genes and environment to kindergarten literacy skills across countries. We also hypothesize an increase in genetic effects on literacy from kindergarten to Grade 1, especially in Scandinavia where formal reading instruction is introduced one year later than in Australia and the U.S. These questions are addressed in the present study through univariate behavior-genetic analyses of data from identical and same-sex fraternal twins tested near the end of kindergarten and first grade. In addition to comparing the magnitudes of genetic and environmental influences between countries and grades in univariate analyses, with a multivariate approach we also address the question whether the same or different sources of genetic and environmental influences account for individual differences in literacy at kindergarten and Grade 1. Based on the differences in the curriculum for literacy instruction across countries summarized above, we hypothesize continuity in the pattern of genetic and environmental influences on reading and spelling from kindergarten to Grade 1 in Australia, but a possible change in genetic and environmental effects on literacy skills in Scandinavia, with the US representing an intermediate case. Method Participants The kindergarten sample comprised a total of 812 same-sex twin pairs recruited from the Colorado Twin Registry in the U.S., the National Heath and Medical Research Council's Australian Twin Registry, and from the Medical Birth Registries in Norway and Sweden (see Actual attrition because of families leaving the project is virtually zero. Only participants for whom the predominant language of their country (i.e., English, Swedish, or Norwegian) was the first language spoken at home were selected. There were no significant differences in parents' mean years of education across twin samples. Also, the means were around 14 years suggesting that level of education is representative for each country. Zygosity was determined by DNA analysis from cheek swab collection, or, in a minority of cases, by selected items from the questionnaire by Literacy skills Reading. Reading skills in kindergarten and Grade 1 were measured by both the word and nonword subtests from the Test of Word Reading Efficiency (TOWRE; Torgesen, Wagner, & Rashotte, 1999), with both Forms A and B administered and averaged to increase reliability (test-retest reliability for children aged 6-9 years, .97 for word and .90 for nonword standard scores). In each Form, children read a list of words and a list of nonwords as quickly as possible in 45 sec. A composite measure of reading skill was created for phenotypic analyses, justified by high correlations, .83 and .86 on average, between word and nonword reading at both kindergarten and at the end of Grade 1. For the behavior genetic analyses, we modelled the four subtests of word and nonword reading as latent traits. Spelling. At kindergarten, spelling was measured by a test developed by Byrne and Fielding- Procedure Children were assessed individually by trained examiners in their homes and/or schools at the end of kindergarten and Grade 1. To foster fidelity of assessment between testers and sites, we have adopted the practice of videotaping samples of test sessions and having each tester inspect the tapes of other testers. In this study, we only report on reading and spelling measures performed at each age. However, in single one-hour sessions at each of kindergarten and Grade 1, several other measures such as phonological awareness, RAN, and verbal abilities were included (for details, see Analysis One-way analyses of variance (ANOVA) and Tukey HSD post hoc tests were performed to test differences between country samples for reading and spelling at kindergarten and Grade 1. The magnitude of the mean differences was calculated using Cohen's d. Genetic and environmental influences on reading and spelling skills across country and within country 11 across time were analyzed using monozygotic (MZ) and dizygotic (DZ) twin correlations, and models were fitted from raw data using maximum likelihood estimation in Mx Results Reading and spelling skills across country Means and standard deviations for reading and spelling at kindergarten and Grade 1 across country and effect size estimations for mean differences are presented in Behavior-genetic analyses Standardized raw data adjusted for age and gender effects within each twin sample were used as input for all behavior-genetic analyses. To estimate the relative influence on individual differences from additive genetic effects (a 2 ), shared-environment effects (c 2 ), and nonsharedenvironment effects (e 2 ), the data for reading and spelling skills were subjected to structural equation modelling by use of the Mx statistical modelling package (Neale, Boker, Xie, & Maes, 2002). In this section, we start by presenting correlations between MZ and DZ twins

A Genetic Epidemiological Mega Analysis of Smoking Initiation in Adolescents

Introduction. Previous studies in adolescents were not adequately powered to accurately disentangle genetic and environmental influences on smoking initiation across adolescence. Methods. Mega-analysis of pooled genetically informative data on smoking initiation was performed, with structural equation modeling, to test equality of prevalence and correlations across cultural backgrounds, and to estimate the significance and effect size of genetic and environmental effects according to the classical twin study, in adolescent male and female twins from same-sex and opposite-sex twin pairs (N=19 313 pairs) between age 10 and 19, with 76 358 longitudinal assessments between 1983 and 2007, from 11 population-based twin samples from the US, Europe and Australia. Results. Although prevalences differed between samples, twin correlations did not, suggesting similar etiology of smoking initiation across developed countries. The estimate of additive genetic contributions to liability of smoking initiation increased from approximately 15% to 45% from age 13 to 19. Correspondingly, shared environmental factors accounted for a substantial proportion of variance in liability to smoking initiation at age 13 (70%) and gradually less by age 19 (40%). Conclusions. Both additive genetic and shared environmental factors significantly contribute to variance in smoking initiation throughout adolescence. The present study, the largest genetic epidemiological study on smoking initiation to date, found consistent results across 11 studies for the etiology of smoking initiation. Environmental factors, especially those shared by siblings in a family, primarily influence smoking initiation variance in early adolescence, while an increasing role of genetic factors is seen at later ages, which has important implications for prevention strategies. IMPLICATIONS: This is the first study to find evidence of genetic factors in liability to smoking initiation at ages as young as 12. It also shows the strongest evidence to date for decay of effects of the shared environment from early adolescence to young adulthood. We found remarkable consistency of twin correlations across studies reflecting similar etiology of liability to initiate smoking across different cultures and time periods. Thus familial factors strongly contribute to individual differences in who starts to smoke with a gradual increase in the impact of genetic factors and a corresponding decrease in that of the shared environment

Product Diversity and Spectrum of Choice in Hospital ePrescribing Systems in England

Background: ePrescribing systems have considerable potential for improving healthcare quality and safety. With growing expectations about the benefits of such systems, there is evidence of widespread plans to implement these systems in hospitals in England where hitherto they have had a low uptake. Given the international drive away from developing home-grown to systems to procuring commercial applications, we aimed to identify available ePrescribing systems in England and to use the findings to develop a taxonomy of the systems offered by suppliers. Methods and Findings: We undertook a scoping review of the published and grey literature, and conducted expert interviews with vendors, healthcare organisations and national ePrescribing experts in order to identify the spectrum of available systems, identify and map their key features, and then iteratively develop and validate a taxonomy of commercial ePrescribing systems available to English hospitals. There is a wide range of available systems including 13 hospital-wide applications and a range of specialty systems. These commercial applications can be grouped into four sub-categories: standalone systems, modules within integrated systems, functionalities spread over several modules, and specialty systems. The findings also reveal that apart from four packaged applications (two of which are specialty systems), all other systems have none or less than two live implementations across England. Conclusions: The wide range of products developed in the last few years by different national and international suppliers, and the low uptake of these products by English hospitals indicate that the English ePrescribing market is still in its infancy. This market is undergoing rapid cycles of change, both with respect to the number of suppliers and their diversity of offerings. Constant renewal of knowledge is needed on the status of this evolving market, encompassing the products development and adoption, to assist implementation decisions and facilitate market maturity

Association between birthweight and later body mass index : an individual-based pooled analysis of 27 twin cohorts participating in the CODATwins project

Background: There is evidence that birthweight is positively associated with body mass index (BMI) in later life, but it remains unclear whether this is explained by genetic factors or the intrauterine environment. We analysed the association between birthweight and BMI from infancy to adulthood within twin pairs, which provides insights into the role of genetic and environmental individual-specific factors. Methods: This study is based on the data from 27 twin cohorts in 17 countries. The pooled data included 78 642 twin individuals (20 635 monozygotic and 18 686 same-sex dizygotic twin pairs) with information on birthweight and a total of 214 930 BMI measurements at ages ranging from 1 to 49 years. The association between birthweight and BMI was analysed at both the individual and within-pair levels using linear regression analyses. Results: At the individual level, a 1-kg increase in birthweight was linearly associated with up to 0.9 kg/m(2) higher BMI (P <0.001). Within twin pairs, regression coefficients were generally greater (up to 1.2 kg/m(2) per kg birthweight, P <0.001) than those from the individual-level analyses. Intra-pair associations between birthweight and later BMI were similar in both zygosity groups and sexes and were lower in adulthood. Conclusions: These findings indicate that environmental factors unique to each individual have an important role in the positive association between birthweight and later BMI, at least until young adulthood.Peer reviewe

Genetic and environmental variation in educational attainment : an individual-based analysis of 28 twin cohorts

We investigated the heritability of educational attainment and how it differed between birth cohorts and cultural-geographic regions. A classical twin design was applied to pooled data from 28 cohorts representing 16 countries and including 193,518 twins with information on educational attainment at 25 years of age or older. Genetic factors explained the major part of individual differences in educational attainment (heritability: a(2)=0.43; 0.41-0.44), but also environmental variation shared by co-twins was substantial (c(2)=0.31; 0.30-0.33). The proportions of educational variation explained by genetic and shared environmental factors did not differ between Europe, North America and Australia, and East Asia. When restricted to twins 30 years or older to confirm finalized education, the heritability was higher in the older cohorts born in 1900-1949 (a(2)=0.44; 0.41-0.46) than in the later cohorts born in 1950-1989 (a(2)=0.38; 0.36-0.40), with a corresponding lower influence of common environmental factors (c(2)=0.31; 0.29-0.33 and c(2)=0.34; 0.32-0.36, respectively). In conclusion, both genetic and environmental factors shared by co-twins have an important influence on individual differences in educational attainment. The effect of genetic factors on educational attainment has decreased from the cohorts born before to those born after the 1950s.Peer reviewe

Association of the OPRM1 Variant rs1799971 (A118G) with Non-Specific Liability to Substance Dependence in a Collaborative de novo Meta-Analysis of European-Ancestry Cohorts

Peer reviewe

Distinct Loci in the CHRNA5 / CHRNA3 / CHRNB4 Gene Cluster Are Associated With Onset of Regular Smoking

Neuronal nicotinic acetylcholine receptor (nAChR) genes (CHRNA5/CHRNA3/CHRNB4) have been reproducibly associated with nicotine dependence, smoking behaviors, and lung cancer risk. Of the few reports that have focused on early smoking behaviors, association results have been mixed. This meta-analysis examines early smoking phenotypes and SNPs in the gene cluster to determine: (1) whether the most robust association signal in this region (rs16969968) for other smoking behaviors is also associated with early behaviors, and/or (2) if additional statistically independent signals are important in early smoking. We focused on two phenotypes: age of tobacco initiation (AOI) and age of first regular tobacco use (AOS). This study included 56,034 subjects (41 groups) spanning nine countries and evaluated five SNPs including rs1948, rs16969968, rs578776, rs588765, and rs684513. Each dataset was analyzed using a centrally generated script. Meta-analyses were conducted from summary statistics. AOS yielded significant associations with SNPs rs578776 (beta = 0.02, P = 0.004), rs1948 (beta = 0.023, P = 0.018), and rs684513 (beta = 0.032, P = 0.017), indicating protective effects. There were no significant associations for the AOI phenotype. Importantly, rs16969968, the most replicated signal in this region for nicotine dependence, cigarettes per day, and cotinine levels, was not associated with AOI (P = 0.59) or AOS (P = 0.92). These results provide important insight into the complexity of smoking behavior phenotypes, and suggest that association signals in the CHRNA5/A3/B4 gene cluster affecting early smoking behaviors may be different from those affecting the mature nicotine dependence phenotype

Genome-wide association meta-analysis of age at first cannabis use

Cannabis is one of the most commonly used substances among adolescents and young adults. Earlier age at cannabis initiation is linked to adverse life outcomes including multi-substance use and dependence. This study estimated the heritability of age at first cannabis use and identify associations with genetic variants. A twin-based heritability analysis using 8,055 twins from three cohorts was performed. We then carried-out a genome wide survival meta-analysis of age at first cannabis use in a discovery sample of 24,953 individuals from nine European, North American, and Australian cohorts, and a replication sample of 3,735 individuals. The twin-based heritability for age at first cannabis use was 38% (95% confidence interval [CI] 19-60%). Shared and unique environmental factors explained 39% (95% CI 20-56%) and 22% (95% CI 16-29%). The genome wide survival meta-analysis identified five SNPs on chromosome 16 within the Calcium-transporting ATPase gene (ATP2C2) at P 0.8) with the strongest association at the intronic variant rs1574587 (P=4.09E-09). Gene-based tests of association identified the ATP2C2 gene on 16q24.1 (P=1.33e-06). Although the five SNPs and ATP2C2 did not replicate, ATP2C2 has been associated with cocaine dependence in a previous study. ATP2B2, which is a member of the same calcium signalling pathway, has been previously associated with opioid dependence. SNP-based heritability for age at first cannabis use was non-significant. Age at cannabis initiation appears to be moderately heritable in Western countries, and individual differences in onset can be explained by separate but correlated genetic liabilities. The significant association between age of initiation and ATP2C2 is consistent with the role of calcium signalling mechanisms in substance use disorders