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The International Collaboration for Autism Registry Epidemiology (iCARE) is the first multinational research consortium (Australia, Denmark, Finland, Israel, Norway, Sweden, USA) to promote research in autism geographical and temporal heterogeneity, phenotype, family and life course patterns, and etiology. iCARE devised solutions to challenges in multinational collaboration concerning data access security, confidentiality and management. Data are obtained by integrating existing national or state-wide, population-based, individual-level data systems and undergo rigorous harmonization and quality control processes. Analyses are performed using database federation via a computational infrastructure with a secure, web-based, interface. iCARE provides a unique, unprecedented resource in autism research that will significantly enhance the ability to detect environmental and genetic contributions to the causes and life course of autism.

Prevalence statistics for autism spectrum disorders (ASD) vary widely across geographical boundaries. Some variation can be explained by diagnostic methods, case ascertainment and age at diagnosis. This study compared prevalence statistics for two distinct geographical regions, Denmark and Western Australia, both of which have had population-based registers and consistent classification systems operating over the past decade. Overall ASD prevalence rates were higher in Denmark (68.5 per 10,000 children) compared with Western Australia (51.0 per 10,000 children), while the diagnosis of childhood autism was more prevalent in Western Australia (39.3 per 10,000 children) compared with Denmark (21.8 per 10,000 children). These differences are probably caused by local phenomena affecting case ascertainment but influence from biological or geographical factors may exist.

Aim: To evaluate the effects of a physical activity programme on sedentary behaviour and physical activity in ambulant individuals with Rett syndrome (RTT). Method: In this multicentre randomized waitlist‐controlled trial, we recruited 43 ambulatory individuals with RTT in Australia and Denmark. Adequate baseline data were obtained from 38 participants (mean age 20 years, range 6–41, SD 10 years 6 months, one male). All completed the trial. Participants received 12 weeks of usual care (n = 19) or a goal‐based, telehealth‐supported programme in which activities occurred in their familiar environments (n = 19). Sedentary time and daily steps were assessed at baseline, post‐test, and 12‐week follow‐up. The data analyst was blinded to group allocation. Results: Sedentary time decreased in the intervention group by 2.7% (95% confidence interval [CI] −6.0 to 0.6) and increased in the control group by 1.3% (95% CI −4.8 to 7.4). Intervention and control groups increased the number of their steps per day by 264.7 (95% CI −72.2 to 601.5) and 104.8 (95% CI −178.1 to 387.7) respectively. No significant differences were found on any outcomes at post‐test. There were three minor adverse events. Interpretation: A goal‐based telehealth intervention seemed to produce small improvements in physical activity for individuals with RTT. Families require more support to increase these individuals' extremely low physical activity levels. What this paper adds: A telehealth‐supported intervention may produce small changes in physical activity in Rett syndrome (RTT).Increasing physical activity in individuals with RTT is challenging for caregivers.Families require substantial out‐of‐home support to increase their children's activity levels. [ABSTRACT FROM AUTHOR]

Importance: The origins and development of autism spectrum disorder (ASD) remain unresolved. No individual-level study has provided estimates of additive genetic, maternal, and environmental effects in ASD across several countries.Objective: To estimate the additive genetic, maternal, and environmental effects in ASD.Design, Setting, and Participants: Population-based, multinational cohort study including full birth cohorts of children from Denmark, Finland, Sweden, Israel, and Western Australia born between January 1, 1998, and December 31, 2011, and followed up to age 16 years. Data were analyzed from September 23, 2016 through February 4, 2018.Main Outcomes and Measures: Across 5 countries, models were fitted to estimate variance components describing the total variance in risk for ASD occurrence owing to additive genetics, maternal, and shared and nonshared environmental effects.Results: The analytic sample included 2 001 631 individuals, of whom 1 027 546 (51.3%) were male. Among the entire sample, 22 156 were diagnosed with ASD. The median (95% CI) ASD heritability was 80.8% (73.2%-85.5%) for country-specific point estimates, ranging from 50.9% (25.1%-75.6%) (Finland) to 86.8% (69.8%-100.0%) (Israel). For the Nordic countries combined, heritability estimates ranged from 81.2% (73.9%-85.3%) to 82.7% (79.1%-86.0%). Maternal effect was estimated to range from 0.4% to 1.6%. Estimates of genetic, maternal, and environmental effects for autistic disorder were similar with ASD.Conclusions and Relevance: Based on population data from 5 countries, the heritability of ASD was estimated to be approximately 80%, indicating that the variation in ASD occurrence in the population is mostly owing to inherited genetic influences, with no support for contribution from maternal effects. The results suggest possible modest differences in the sources of ASD risk between countries. [ABSTRACT FROM AUTHOR]

Background: Rett syndrome (RTT) is a rare neurodevelopmental disorder leading to multiple disabilities and high dependency on caregivers. This study aimed to: (1) describe the patterns of sedentary time and daily steps and (2) identify the association of individual and environmental characteristics with sedentary time. Methods: All Danish females with RTT older than 5 years of age and with a MECP2 mutation were invited to participate. The activPAL and StepWatch Activity Monitor (SAM) were worn by participants for at least four days. Sedentary time and step counts were plotted by time to examine daily activity patterns. Associations between sedentary time and individual and environmental covariates were assessed with linear regression models. Results: The median (interquartile range) age of participants was 22.0 (14.3-36.5) years. On average 83.3% (standard deviation 13.9%) of waking hours were spent in sedentary behaviours (n = 48) and the median (interquartile range) daily step count was 5128 (2829-7704) (n = 28). Females older than 33.5 years, and those unable to walk independently were more sedentary. Conclusions: This study demonstrated high levels of sedentary time and low daily step counts in a Danish population of females with RTT. Advancing age and lower walking skills were associated with higher levels of sedentary time. Implications for Rehabilitation: Sedentary lifestyles in individuals with disabilities have a negative impact on health and quality of life. High levels of sedentary time and low daily step counts were demonstrated in a Danish population of females with Rett syndrome. Advancing age and inability to walk independently were strongly associated with higher levels of sedentary time in females with Rett syndrome. Understanding patterns of sedentary behaviour and physical activity can aid health care professionals in developing health-promoting physical activity interventions. [ABSTRACT FROM AUTHOR]

Background:The repertoire of measures of walking in Rett syndrome is limited. This study aimed to determine measurement properties of a modified two-minute walk test (2MWT) and a modified Rett syndrome-specific functional mobility scale (FMS-RS) in Rett syndrome. Methods:Forty-two girls and women with Rett syndrome (median 18.4 years, range 2.4–60.9 years) were assessed for clinical severity, gross motor skills, and mobility. To measure walking capacity, 27 of this group completed a 2MWT twice on two different assessment days. To assess walking performance, the FMS-RS was administered to the total sample of parents (n = 42) on two occasions approximately one week apart. Results:There were negative correlations between clinical severity and 2MWT (r = −0.48) and FMS-RS (r = −0.60–0.66). There were positive correlations between gross motor skills and mobility and 2MWT (r = 0.51, 0.43) and FMS-RS (r = 0.71–0.93, 0.74–0.94), respectively. Test–retest reliability for the 2MWT was good with high intraday and interday correlations (ICC = 0.86–0.98). For the 2MWT, the standard error of measurement was 13.8 m and we would be 95% confident that changes greater than 38 m would be greater than within subject error. There was good test–retest reliability for all three distances on the FMS-RS (ICC = 0.94–0.99). Conclusions:Walking capacity as measured by the 2MWT showed expected but limited relationships with measures of different constructs, providing some support for concurrent validity. Walking performance as measured with the FMS-RS was more strongly consistent with other clinical measures supporting its concurrent validity. Test–retest reliability was good for both the FMS-RS and the 2MWT. Therefore, these measures have the potential to be used in clinical practice and research. Implications for RehabilitationWalking is one of the commonest daily physical activities in ambulant girls and women with RTT. Comprehensive knowledge about the walking abilities in this population is limited.Evidence of validity and test–retest reliability have been demonstrated for the modified two-minute walk test (2MWT) and the Rett syndrome-specific functional mobility scale (FMS-RS).The 2MWT and FMS-RS offer detailed information of the capacity and performance of walking, respectively, in girls and women with RTT [ABSTRACT FROM AUTHOR]

Season of birth has been hypothesized to be a risk factor for autism spectrum disorder (ASD). However, the evidence has been mixed and limited due to methodological challenges. We examine ASD birth trends for 5,464,628 births across 5 countries. ASD birth prevalence data were obtained from the International Collaboration for Autism Registry Epidemiology database, including children born in Denmark, Finland, Norway, Sweden, and Western Australia. Empirical mode decomposition and cosinor modeling were used to assess seasonality. We show seasonal variation in ASD births for the countries of Finland and Sweden. There was a modest increase in risk for children born in the fall and a modest decrease in risk for children born in the spring. Solar radiation levels around conception and the postnatal period were inversely correlated with seasonal trends in ASD risk. In the first multinational study of birth seasonality of ASD, there was evidence supporting the presence of seasonal trends in Finland and Sweden. The observations that risk was highest for fall births (i.e., conceived in the winter) and lowest for spring births (i.e., conceived in the summer), and sunlight levels during critical neurodevelopmental periods explained much of the seasonal trends, are consistent with the hypothesis that a seasonally fluctuating risk factor may influence risk of ASD.

Low Apgar score has been associated with higher risk for several neurological and psychiatric disorders, including cerebral palsy and intellectual disability. Studies of the association between Apgar score and autism spectrum disorder (ASD) have been inconsistent. We aimed to investigate (1) the association between low Apgar score at 5 min and risk for ASD, and (2) the modifying effects of gestational age and sex on this association in the largest multinational database of ASD. We included prospective data from 5.5 million individuals and over 33,000 cases of ASD from Norway, Sweden, Denmark and Western Australia who were born between 1984 and 2007. We calculated crude and adjusted risk ratios (RR) with 95% confidence intervals (95% CIs) for the associations between low Apgar score and ASD. All analyses for ASD were repeated for autistic disorder (AD). We used interaction terms and stratified analysis to investigate the effects of sex, gestational age, and birth weight on the association. In fully adjusted models, low Apgar scores (1-3) (RR, 1.42; 95% CI, 1.16-1.74), and intermediate Apgar scores (4-6) (RR, 1.50; 95% CI, 1.36-1.65) were associated with a higher RR of ASD than optimal Apgar score (7-10). The point estimates for low (RR, 1.88; 95% CI, 1.41-2.51) and intermediate Apgar score (RR, 1.54; 95% CI, 1.32-1.81) were larger for AD than for ASD. This study suggests that low Apgar score is associated with higher risk of ASD, and in particular AD. We did not observe any major modifying effects of gestational age and sex, although there seems to be substantial confounding by gestational age and birth weight on the observed association.

Rett syndrome is a pervasive neurodevelopmental disorder associated with a pathogenic mutation on the MECP2 gene. Impaired movement is a fundamental component and the Rett Syndrome Gross Motor Scale was developed to measure gross motor abilities in this population. The current study investigated the validity and reliability of the Rett Syndrome Gross Motor Scale. Video data showing gross motor abilities supplemented with parent report data was collected for 255 girls and women registered with the Australian Rett Syndrome Database, and the factor structure and relationships between motor scores, age and genotype were investigated. Clinical assessment scores for 38 girls and women with Rett syndrome who attended the Danish Center for Rett Syndrome were used to assess consistency of measurement. Principal components analysis enabled the calculation of three factor scores: Sitting, Standing and Walking, and Challenge. Motor scores were poorer with increasing age and those with the p.Arg133Cys, p.Arg294* or p.Arg306Cys mutation achieved higher scores than those with a large deletion. The repeatability of clinical assessment was excellent (intraclass correlation coefficient for total score 0.99, 95% CI 0.93-0.98). The standard error of measurement for the total score was 2 points and we would be 95% confident that a change 4 points in the 45-point scale would be greater than within-subject measurement error. The Rett Syndrome Gross Motor Scale could be an appropriate measure of gross motor skills in clinical practice and clinical trials.