Helen Margaret Leonard

Helen Margaret Leonard
University of Western Australia | UWA · Centre for Child Health Research

MBChB MPH

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394
Publications
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Publications

Publications (394)
Article
Objective To compare quality of life (QOL) across diagnoses associated with intellectual disability, construct QOL profiles and evaluate membership by diagnostic group, function and comorbidities. Method Primary caregivers of 526 children with intellectual disability (age 5–18 years) and a diagnosis of cerebral palsy, autism spectrum disorder, Dow...
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Prader-Willi syndrome (PWS) is a rare genetic disorder characterised by neurodevelopmental delays, hyperphagia, difficulties with social communication and challenging behaviours. Individuals require intensive supervision from caregivers which may negatively affect caregiver quality of life. This study used data collected in the Australasian PWS Reg...
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Aim: This systematic review aimed to identify the most important social, environmental, biological, and/or genetic risk factors for intellectual disability (ID). Methods: Eligible were published prospective or retrospective comparative studies investigating risk factors for ID in children 4-18 years. Exclusions were single group studies with no...
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Background While Aboriginal Australians are known to be disproportionately affected by intellectual disabilities (ID) and/or autism spectrum disorders (developmental disabilities), true prevalences among Aboriginal children are unclear, with evidence of delayed and missed diagnoses and barriers to services. This study estimated these prevalences an...
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This study investigated the influence of factors at birth and in infancy on the likelihood of achieving major motor milestones in CDKL5 Deficiency Disorder (CDD). Data on 350 individuals with a pathogenic CDKL5 variant was sourced from the International CDKL5 Disorder Database. A first model included factors available at birth (e.g., sex, variant g...
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The natural history of MECP2 duplication syndrome (MDS), a rare X-linked neurodevelopmental disorder with an estimated birth prevalence of 1/150,000 live births, is poorly understood due to a lack of clinical data collected for research. Such information is critical to the understanding of disease progression, therapeutic endpoints and outcome meas...
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Individuals with Prader-Willi syndrome (PWS) often have excessive daytime sleepiness and emotional/behavioral disturbances. The objective of this study was to examine whether daytime sleepiness was associated with these emotional/behavioral problems, independent of nighttime sleep-disordered breathing, or the duration of sleep. Caregivers of indivi...
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Background: This population-based cohort study investigated dental procedures in the hospital setting in Western Australian children with or without intellectual disability and/or autism spectrum disorder aged up to 18 years. Considering previously reported disparities in dental disease between Indigenous and non-Indigenous Australian children, th...
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Since the discovery of MECP2 duplication syndrome (MDS) in 1999, efforts to characterise this disorder have been limited by a lack of large datasets, with small case series often favouring the reporting of certain conditions over others. This study is the largest to date, featuring 134 males and 20 females, ascertained from the international MECP2...
Article
Pathogenic variants in the CDKL5 gene result in CDKL5 deficiency disorder (CDD), which is characterized by early-onset epilepsy, severe developmental delay, and often, cortical visual impairment. Validated clinical outcome measures are needed for future clinical trials to be successful. This study aimed to adapt the Rett Syndrome Hand Function Scal...
Article
Cyclin‐dependent kinase‐like 5 (CDKL5) gene pathogenic variants result in CDKL5 deficiency disorder (CDD). Early onset intractable epilepsy and severe developmental delays are prominent symptoms of CDD. Comorbid sleep disturbances are a major concerning symptom for families. We aimed to explore the relationship between insomnia, daytime sleepiness,...
Article
CDKL5 deficiency disorder (CDD) was first identified as a cause of human disease in 2004. Although initially considered a variant of Rett syndrome, CDD is now recognised as an independent disorder and classified as a developmental epileptic encephalopathy. It is characterised by early-onset (generally within the first 2 months of life) seizures tha...
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Background Accurate knowledge of the relationship between craniofacial anomalies (CFA), intellectual disability (ID) and autism spectrum disorder (ASD) is essential to improve services and outcomes. The aim is to describe the association between CFA, ID and ASD using linked population data. Methods All births (1983–2005; n = 566,225) including CFA...
Article
Intellectual and developmental disabilities are heterogeneous in aetiology and presentation, and one cannot make assumptions about the oral health barriers of those with Rett syndrome (RTT) based on findings from generic studies. This study investigated caregivers’ perceptions regarding access to dental care for those with (RTT), and associations o...
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Rett syndrome is associated with severe functional impairments and many comorbidities, each in urgent need of treatments. Mutations in the MECP2 gene were identified as causing Rett syndrome in 1999. Over the past 20 years there has been an abundance of preclinical research with some studies leading to human clinical trials. Despite this, few viabl...
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Full-text available
MECP2 duplication syndrome (MDS) is a rare, X-linked, neurodevelopmental disorder caused by a duplication of the methyl-CpG-binding protein 2 (MECP2) gene—a gene in which loss-of-function mutations lead to Rett syndrome (RTT). MDS has an estimated live birth prevalence in males of 1/150,000. The key features of MDS include intellectual disability,...
Article
Aim: To identify factors associated with quality of life (QoL) in children with intellectual disability. We aimed to identify patterns of association not observable in previous hypothesis-driven regression modelling using the same data set from a cross-sectional observational study. Method: A questionnaire was completed by 442 caregivers of chil...
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CDKL5 deficiency disorder (CDD), a severe developmental and epileptic encephalopathy, is being diagnosed earlier with improved access to genetic testing, but this may also have unanticipated impacts on parents’ experience receiving the diagnosis. This study explores the lived experience of parents receiving a diagnosis of CDD for their child using...
Article
Objective To describe trends, age, and sex-specific patterns of population hospital admissions with a diagnosis of craniosynostosis (CS) in Australia. Data Source Population data for hospital separations (in-patient) from public and private hospitals (July 1996-June 2018) were obtained from the publicly available Australian Institute of Health an...
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Objective The study investigated the effect of seizure and medication burden at initial contact with the International CDKL5 Disorder Database on subsequent development and clinical severity and compared quality of life among those whose development progressed, remained stable, or regressed between baseline and follow-up. Methods The effects of se...
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Purpose People with a disability may spend more time sitting and lying (“downtime”) and less time standing and walking (“uptime”). Caregivers and therapists supporting individuals with Rett syndrome were surveyed, aiming to gather insights on how to support participation in “uptime” activities. Method An anonymous online survey including open ende...
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PurposeThe measurement of quality of life (QOL) in children with intellectual disability often relies upon proxy report via caregivers. The current study investigated whether caregiver psychological distress mediates or moderates the effects of impairment on their ratings of QOL in children with intellectual disability.Methods Caregivers of 447 chi...
Article
Objective To describe birth prevalence of rare craniofacial anomalies and associations with antenatal and perinatal factors. Study design All live and stillbirths in Western Australia between 1980 and 2010 were identified from the Western Australian Birth Registrations and the Midwives Notification System (also provides information on antenatal an...
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Background Craniosysnostosis (CS) is a condition ensuing from premature fusion of cranial sutures, resulting in altered craniofacial morphology, requiring early neurosurgical interventions to improve prognosis and outcomes. This study aimed to describe total population hospital admissions related to craniosynostosis in Australia over a 22-year peri...
Article
Objective To describe patterns and demographic characteristics of total-population hospital admissions with a diagnosis of Treacher Collins syndrome (TCS) in Australia. Data Source Population summary data for inpatient hospitals admissions (public and private) with a principal diagnosis of TCS (ICD10-AM-Q87.04) were obtained from the Australian In...
Article
CDKL5 deficiency disorder (CDD) results in early-onset seizures and severe developmental impairments. A CDD clinical severity assessment (CCSA) was previously developed with clinician and parent-report items to capture information on a range of domains. Consistent with US Food and Drug Administration (FDA) guidelines, content validation is the firs...
Article
It is biologically plausible that risk of autism spectrum disorder (ASD) is elevated by both short and long interpregnancy intervals (IPI). We conducted a retrospective cohort study of singleton, non-nulliparous live births, 1998–2007 in Denmark, Finland, and Sweden (N = 925,523 births). Optimal IPI was defined as the IPI at which minimum risk was...
Article
Purpose This study investigated dental hospitalisations in Western Australian (WA) children with intellectual disability (ID) and/or autism spectrum disorder (ASD) aged up to 18 years. Methods Data on WA live births from 1983 to 2004 from the WA Midwives Notification System were linked to the Intellectual Disability Exploring Answers database, the...
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Introduction CDKL5 Deficiency Disorder (CDD) is a severe treatment-resistant form of early-onset epilepsy. Current treatment options are often ineffective and associated with adverse effects, forcing families to seek alternative therapies for their children including products derived from cannabis. Reports of miraculous cures and a public preferenc...
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Objective: To investigate the longitudinal stability of hand function in Rett syndrome and to analyze further the relationships between stability of hand function and genotype, age and walking ability. Study design: Longitudinal video data of functional abilities of individuals with genetically confirmed Rett syndrome were collected by families...
Article
Background There is a dearth of literature available on the comparative oral health status of those with Rett syndrome (RTT) despite diurnal bruxism being a supportive diagnostic criterion for the disorder. This study was designed to investigate the dental experiences of individuals with RTT in terms of perceived at-home and professional dental car...
Article
Children with intellectual disabilities are more likely to experience sleep disorders of insomnia, excessive daytime sleepiness and sleep breathing disorders than typically developing children. The present study examined risk factors for these sleep disorders in 447 children (aged 5–18 years), diagnosed with an intellectual disability and comorbid...
Article
Background: Many children with intellectual disability live with medical comorbidities. This study examined the impacts of comorbidities on quality of life (QOL) of children with intellectual disabilities and whether impacts varied with caregiver perceptions that medical needs had been met. Methods: Primary caregivers of 447 children (aged 5-19...
Article
Background CDKL5 Deficiency Disorder (CDD) is a rare genetic disorder caused by a mutation in the cyclin-dependent kinase-like 5 (CDKL5) gene. It is now considered to be a developmental and epileptic encephalopathy because of the early onset of seizures in association with severe global delay. Other features include cortical visual impairment, slee...
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Introduction Individuals with Rett syndrome (RTT) experience impaired gross motor skills, limiting their capacity to engage in physical activities and participation in activities. There is limited evidence of the effectiveness of supported physical activity interventions. This study aims to evaluate the effects of a telehealth-delivered physical ac...
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Objective To review the effectiveness of oral health education and oral health promotion interventions for children and adolescents with intellectual and developmental disabilities (IDD), in ensuring optimal gingival health, caries experience and oral health‐related quality of life, compared to no interventions or alternative interventions. Method...
Article
Characterized by early-onset seizures, global developmental delay and severe motor deficits, CDKL5 deficiency disorder is caused by pathogenic variants in the cyclin-dependent kinase-like 5 gene. Previous efforts to investigate genotype-phenotype relationships have been limited due to small numbers of recurrent mutations and small cohort sizes. Usi...
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Background Rett syndrome is a genetically caused neurodevelopmental disorder associated with functional deficits and comorbidities. This study investigated relationships between genotype, functional abilities and comorbidities and quality of life in Rett syndrome. Methods The International Rett Syndrome Database, InterRett, was used as a sampling...
Article
Alcohol exposure during pregnancy has been associated with altered brain development and facial dysmorphology. While autism spectrum disorder (ASD) is not specifically related to distinct facial phenotypes, recent studies have suggested certain facial characteristics such as increased facial masculinity and asymmetry may be associated with ASD and...
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Aims To investigate associations between functioning, community participation, and quality of life (QoL) and identify whether participation mediates the effects of functioning on QoL. Method The caregivers of 435 children (211 females, 224 males; mean age 12y; SD 3y 11mo; age range 5–18y) with intellectual disability and autism spectrum disorder,...
Article
Cyclin-dependent–like kinase 5 ( CDKL5 ) gene mutations lead to an X-linked disorder that is characterized by infantile epileptic encephalopathy, developmental delay, and hypotonia. However, we found that a substantial percentage of these patients also report a previously unrecognized anamnestic deficiency in pain perception. Consistent with a role...
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Purpose: To investigate modifiable child and caregiver factors influencing community participation among children with Down syndrome. Methods: Cross-sectional data from a study investigating quality of life of children with intellectual disability were analysed. Participants were caregivers of 89 children with Down syndrome (54 females; 83 school a...
Article
Background Children and adolescents with intellectual disability are at risk of developing psychiatric symptoms and disorders; yet, the estimates reported in the literature have been inconsistent, presenting a potential barrier for service planning and delivery. Sources of variability could arise from differences in measurement instruments as well...
Preprint
Full-text available
Background CDKL5 Deficiency Disorder (CDD) is a rare genetic disorder caused by a mutation in the cyclin-dependent kinase-like 5 (CDKL5) gene. It is now considered to be a developmental and epileptic encephalopathy because of the early onset of seizures in association with severe global delay. Other features include cortical visual impairment, slee...
Article
Objective: To assess responsiveness and reproducibility using the estimates of test-retest reliability for the Quality of Life Inventory-Disability (QI-Disability), accounting for changes in child health and parental stress. Method: Quality of Life Inventory-Disability was administered twice over a 1-month period to a sample of 55 primary caregi...
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Background Positive health outcomes have been observed following gastrostomy insertion in children with intellectual disability, which is being increasingly used at younger ages to improve nutritional intake. This study investigated the effect of gastrostomy insertion on survival of children with severe intellectual disability. Methods We used lin...
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Objective Children with intellectual disability and marked feeding difficulties may undergo gastrostomy insertion to assist with their nutritional and medication needs. Use has increased recently for younger children, and it is intended to provide long-term support. This study explored the perceived value of gastrostomy for the quality of life (QOL...
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Quantification of stillbirth risk has potential to support clinical decision-making. Studies that have attempted to quantify stillbirth risk have been hampered by small event rates, a limited range of predictors that typically exclude obstetric history, lack of validation, and restriction to a single classifier (logistic regression). Consequently,...
Article
Pathogenic variants in the cyclin‐dependent kinase‐like 5 (CDKL5) gene cause the neurodevelopmental disorder, the CDKL5 deficiency disorder. Reports of individuals with pathogenic variants in CDKL5 without seizures are exceedingly rare, and in‐depth analyses of their variants have been lacking. Whole‐genome sequencing was performed on a 29‐year‐old...
Article
Objective: The behavioral phenotype of neurogenetic disorders associated with intellectual disability often includes psychiatric comorbidity. The objectives of this systematic review and meta-analysis were to systematically review the prevalence of psychiatric disorders and symptoms in children and adolescents with these disorders and compare phen...
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Background: Preterm birth is a known risk factor for infant development but it is less clear whether fetal growth restriction (FGR) and early term birth between 37 and 39 weeks gestation are associated with risks for infant development. Aims: This study investigated risk factors for adverse developmental outcomes at 12 months of age in a populat...
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Objective: To examine the frequency of hospital admissions before and after gastrostomy insertion in children with severe intellectual disability. Study design: We conducted a retrospective cohort study using linked health administrative and disability data from Western Australia (WA) and New South Wales (NSW). Children born between 1983 and 200...
Article
Background: Pregnancy in women with intellectual disability (ID) is increasingly recognised, along with their increased likelihood of experiencing risk factors for adverse pregnancy and infant outcomes. Objectives: We aimed to compare risks of socio-demographic, pregnancy and infant outcomes of women with ID to other women. Methods: All mother...
Article
Data linkage holds great promise for generating new information about people with intellectual and developmental disabilities (IDD) as a population, yet few centers have developed the infrastructure to utilize this methodology. Two examples, from Canada and Australia, describe their efforts in building data linkage capabilities, and how linked data...
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Full-text available
Objectives Our overall aim was to evaluate the Western Australian Intellectual Disability Exploring Answers (IDEA) surveillance system. The primary objective was to evaluate the attributes of the system. The secondary objective was to provide recommendations to data custodians and stakeholders to strengthen the system. Method The IDEA system was e...
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Aim: To compare hospital admission patterns after the first year of life in Australian children with developmental disabilities and children with no known disability, according to maternal country of birth and Indigenous status. Method: This was a retrospective cohort study using linked data across health, disability, and hospital admission data...
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An increased prevalence of autism spectrum disorder (ASD) among children of immigrant backgrounds has been observed but clinical profiles are rarely compared. Diagnostic data from children with ASD notified to the Western Australian Register for Autism Spectrum Disorders were analysed according to maternal-race ethnicity and country of birth. A tot...
Article
Objective: To describe the long-term neurodevelopmental and cognitive outcomes for children born preterm. Study design: In this retrospective cohort study, information on children born in Western Australia between 1983 and 2010 was obtained through linkage to population databases on births, deaths, and disabilities. For the purpose of this study...
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Background: To compare the prevalence of preterm birth, post term birth, intra-uterine growth restriction and distribution of Apgar scores in offspring of foreign-born women in Western Australia with that of their Australian-born non-Indigenous and Indigenous counterparts. Methods: A population-based linked data study, involving 767,623 singleto...
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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 Epidemi...
Article
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 Particip...
Preprint
Full-text available
Alcohol exposure during pregnancy has been associated with altered brain development and facial dysmorphology. While autism spectrum disorder (ASD) is not specifically related to distinct facial phenotypes, recent studies have suggested certain facial characteristics—increased facial masculinity and asymmetry—may be associated with ASD and its clin...
Preprint
Cyclin-dependent-like kinase 5 ( Cdkl5) gene mutations lead to an X-linked disorder that is characterized by infantile epileptic encephalopathy, developmental delay and hypotonia. However, we found that a substantial percentage of these patients also report a previously unrecognised anamnestic deficiency in pain perception. Consistent with a role i...
Article
Full-text available
Prader‐Willi syndrome (PWS) is a rare genetic condition with multi‐system involvement. The literature was reviewed to describe neurodevelopment and the behavioural phenotype, endocrine and metabolic disorders and respiratory and sleep functioning. Implications for child and family quality of life were explored. Challenging behaviours contribute to...
Article
Background: Focus is shifting to better understand the lived experiences of children with intellectual disability in relation to their quality of life (QOL). Yet no available QOL measures are grounded in the domains important for this population. We previously conducted qualitative parent caregiver interviews identifying QOL domains in children wit...
Article
Purpose: Rett syndrome (RTT) is a rare neurodevelopmental disorder mainly affecting females and is caused by a mutation in the MECP2 gene. Recent research identified the domains of quality of life (QOL) important for children with RTT but there has been no investigation of domains important for adults. This qualitative study explored QOL in adults...
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Full-text available
Little longitudinal research has examined parental well-being in those with a child with specific genetic developmental disorder although the associated severe neurological impairments and multiple physical comorbidities likely place substantial burden of caregiving on the parent. We aimed to examine longitudinally the well-being of parents of indi...